<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
<!--Generated by ThunderDome XBRL - 01:40AM UTC 2019-03-14--><link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedLabel" xlink:type="simple"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedPeriodEndLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodEndLabel" xlink:type="simple"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedPeriodStartLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodStartLabel" xlink:type="simple"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTotalLabel" xlink:type="simple"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTerseLabel" xlink:type="simple"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedNetLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedNetLabel" xlink:type="simple"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/netLabel" xlink:href="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd#netLabel" xlink:type="simple"/>
  <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:type="extended">
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_DocumentAndEntityInformation" xlink:label="bcrx_DocumentAndEntityInformation" xlink:type="locator"/>
    <link:label xlink:label="bcrx_DocumentAndEntityInformation-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document And Entity Information</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_DocumentAndEntityInformation" xlink:to="bcrx_DocumentAndEntityInformation-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeLossOnDerivative" xlink:label="us-gaap_DerivativeLossOnDerivative" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DerivativeLossOnDerivative-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DerivativeLossOnDerivative</link:label>
    <link:label xlink:label="us-gaap_DerivativeLossOnDerivative-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative, Loss on Derivative</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeLossOnDerivative" xlink:to="us-gaap_DerivativeLossOnDerivative-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expected Dividend Yield</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear" xlink:label="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear" xlink:type="locator"/>
    <link:label xlink:label="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Next Year</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Employee service share-based compensation nonvested awards compensation cost expected to be recognized next year.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear" xlink:to="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_DebtInstrumentMinimumLibor" xlink:label="bcrx_DebtInstrumentMinimumLibor" xlink:type="locator"/>
    <link:label xlink:label="bcrx_DebtInstrumentMinimumLibor-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_DebtInstrumentMinimumLibor</link:label>
    <link:label xlink:label="bcrx_DebtInstrumentMinimumLibor-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Minimum LIBOR</link:label>
    <link:label xlink:label="bcrx_DebtInstrumentMinimumLibor-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The minimum LIBOR interest that will be added to the basis spread.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_DebtInstrumentMinimumLibor" xlink:to="bcrx_DebtInstrumentMinimumLibor-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NoteToFinancialStatementDetailsTextual" xlink:label="bcrx_NoteToFinancialStatementDetailsTextual" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NoteToFinancialStatementDetailsTextual-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note To Financial Statement Details Textual</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NoteToFinancialStatementDetailsTextual" xlink:to="bcrx_NoteToFinancialStatementDetailsTextual-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-significant-accounting-policies-policies" xlink:label="bcrx_statement-statement-significant-accounting-policies-policies" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-significant-accounting-policies-policies-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Significant Accounting Policies</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-significant-accounting-policies-policies" xlink:to="bcrx_statement-statement-significant-accounting-policies-policies-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-tables" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-tables" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income tax benefit at federal statutory rate (21% for 2018 and 2017 and 35 % for 2016)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:to="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-2-property-and-equipment-tables" xlink:label="bcrx_statement-statement-note-2-property-and-equipment-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-2-property-and-equipment-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 2 - Property and Equipment</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-2-property-and-equipment-tables" xlink:to="bcrx_statement-statement-note-2-property-and-equipment-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Risk-Free Interest Rate</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-4-senior-credit-facility-tables" xlink:label="bcrx_statement-statement-note-4-senior-credit-facility-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-4-senior-credit-facility-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 4 - Senior Credit Facility</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-4-senior-credit-facility-tables" xlink:to="bcrx_statement-statement-note-4-senior-credit-facility-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Maturing in one year or less</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-tables" xlink:label="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 5 - Lease Obligations and Other Contingencies</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-tables" xlink:to="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeGainOnDerivative" xlink:label="us-gaap_DerivativeGainOnDerivative" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DerivativeGainOnDerivative-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DerivativeGainOnDerivative</link:label>
    <link:label xlink:label="us-gaap_DerivativeGainOnDerivative-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative, Gain on Derivative</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeGainOnDerivative" xlink:to="us-gaap_DerivativeGainOnDerivative-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-7-stockbased-compensation-tables" xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 7 - Stock-based Compensation</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-7-stockbased-compensation-tables" xlink:to="bcrx_statement-statement-note-7-stockbased-compensation-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NondesignatedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Not Designated as Hedging Instrument [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NondesignatedMember" xlink:to="us-gaap_NondesignatedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-8-income-taxes-tables" xlink:label="bcrx_statement-statement-note-8-income-taxes-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-8-income-taxes-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 8 - Income Taxes</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-8-income-taxes-tables" xlink:to="bcrx_statement-statement-note-8-income-taxes-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-tables" xlink:label="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-tables" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-tables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 11 - Quarterly Financial Information (Unaudited)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-tables" xlink:to="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-tables-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-fair-value-of-the-companys-investments-by-type-details" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-fair-value-of-the-companys-investments-by-type-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-fair-value-of-the-companys-investments-by-type-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk - Fair Value of the Company's Investments by Type (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-fair-value-of-the-companys-investments-by-type-details" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-fair-value-of-the-companys-investments-by-type-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxDisclosureTextBlock" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureTextBlock" xlink:to="us-gaap_IncomeTaxDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-scheduled-maturity-for-the-companys-investments-details" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-scheduled-maturity-for-the-companys-investments-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-scheduled-maturity-for-the-companys-investments-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk - Scheduled Maturity for the Company's Investments (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-scheduled-maturity-for-the-companys-investments-details" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-scheduled-maturity-for-the-companys-investments-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized (loss) gain on available for sale investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-receivables-details" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-receivables-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-receivables-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk- Summary of Receivables (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-receivables-details" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-receivables-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_HedgingDesignationAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Hedging Designation [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-accrued-expenses-details" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-accrued-expenses-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-accrued-expenses-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk - Accrued Expenses (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-accrued-expenses-details" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-accrued-expenses-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_HedgingDesignationDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Hedging Designation [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_HedgingDesignationDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expected Volatility</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-cumulative-effective-adopted-accounting-pronouncement-details" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-cumulative-effective-adopted-accounting-pronouncement-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-cumulative-effective-adopted-accounting-pronouncement-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk - Cumulative Effective Adopted Accounting Pronouncement (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-cumulative-effective-adopted-accounting-pronouncement-details" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-cumulative-effective-adopted-accounting-pronouncement-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-revenues-details" xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-revenues-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-revenues-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 1 - Significant Accounting Policies and Concentrations of Risk - Summary of Revenues (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-revenues-details" xlink:to="bcrx_statement-statement-note-1-significant-accounting-policies-and-concentrations-of-risk-summary-of-revenues-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LiabilitiesCurrent</link:label>
    <link:label xlink:label="us-gaap_LiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total current liabilities</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Maturities of Long-term Debt [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock" xlink:to="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-2-property-and-equipment-property-and-equipment-details" xlink:label="bcrx_statement-statement-note-2-property-and-equipment-property-and-equipment-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-2-property-and-equipment-property-and-equipment-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 2 - Property and Equipment - Property and Equipment (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-2-property-and-equipment-property-and-equipment-details" xlink:to="bcrx_statement-statement-note-2-property-and-equipment-property-and-equipment-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-4-senior-credit-facility-scheduled-principal-repayments-of-the-credit-facility-details" xlink:label="bcrx_statement-statement-note-4-senior-credit-facility-scheduled-principal-repayments-of-the-credit-facility-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-4-senior-credit-facility-scheduled-principal-repayments-of-the-credit-facility-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 4 - Senior Credit Facility - Scheduled Principal Repayments of the Credit Facility (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-4-senior-credit-facility-scheduled-principal-repayments-of-the-credit-facility-details" xlink:to="bcrx_statement-statement-note-4-senior-credit-facility-scheduled-principal-repayments-of-the-credit-facility-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-minimum-payments-under-operating-lease-obligations-details" xlink:label="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-minimum-payments-under-operating-lease-obligations-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-minimum-payments-under-operating-lease-obligations-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 5 - Lease Obligations and Other Contingencies - Minimum Payments under Operating Lease Obligations (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-minimum-payments-under-operating-lease-obligations-details" xlink:to="bcrx_statement-statement-note-5-lease-obligations-and-other-contingencies-minimum-payments-under-operating-lease-obligations-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expected Life (Year)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-7-stockbased-compensation-stockbased-compensation-allocation-details" xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-stockbased-compensation-allocation-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-stockbased-compensation-allocation-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 7 - Stock-Based Compensation - Stock-based Compensation Allocation (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-7-stockbased-compensation-stockbased-compensation-allocation-details" xlink:to="bcrx_statement-statement-note-7-stockbased-compensation-stockbased-compensation-allocation-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-7-stockbased-compensation-stock-incentive-plan-activities-details" xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-stock-incentive-plan-activities-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-stock-incentive-plan-activities-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 7 - Stock-based Compensation - Stock Incentive Plan Activities (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-7-stockbased-compensation-stock-incentive-plan-activities-details" xlink:to="bcrx_statement-statement-note-7-stockbased-compensation-stock-incentive-plan-activities-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-7-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-incentive-plan-details" xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-incentive-plan-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-7-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-incentive-plan-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 7 - Stock-based Compensation - Weighted Average Assumptions for Stock Option Awards Granted to Employees and Directors Under the Incentive Plan (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-7-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-incentive-plan-details" xlink:to="bcrx_statement-statement-note-7-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-incentive-plan-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-7-sharebased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details" xlink:label="bcrx_statement-statement-note-7-sharebased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-7-sharebased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 7 - Share-Based Compensation - Number of Stock Option Awards Exercisable and their Weighted Average Exercise Price (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-7-sharebased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details" xlink:to="bcrx_statement-statement-note-7-sharebased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-7-sharebased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details" xlink:label="bcrx_statement-statement-note-7-sharebased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-7-sharebased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 7 - Share-Based Compensation - Changes in the Number and Weighted-Average Grant-Date Fair Value (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-7-sharebased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details" xlink:to="bcrx_statement-statement-note-7-sharebased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details" xlink:label="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 8 - Income Taxes - Differences Between the Company's Effective Tax Rate and the Statutory Tax Rate (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details" xlink:to="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals" xlink:label="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 8 - Income Taxes - Differences Between the Company's Effective Tax Rate and the Statutory Tax Rate (Details) (Parentheticals)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals" xlink:to="bcrx_statement-statement-note-8-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-8-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details" xlink:label="bcrx_statement-statement-note-8-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-8-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 8 - Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-8-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details" xlink:to="bcrx_statement-statement-note-8-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-8-income-taxes-components-of-deferred-tax-assets-and-liabilities-details" xlink:label="bcrx_statement-statement-note-8-income-taxes-components-of-deferred-tax-assets-and-liabilities-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-8-income-taxes-components-of-deferred-tax-assets-and-liabilities-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 8 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-8-income-taxes-components-of-deferred-tax-assets-and-liabilities-details" xlink:to="bcrx_statement-statement-note-8-income-taxes-components-of-deferred-tax-assets-and-liabilities-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-schedule-of-quarterly-information-details" xlink:label="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-schedule-of-quarterly-information-details" xlink:type="locator"/>
    <link:label xlink:label="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-schedule-of-quarterly-information-details-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Note 11 - Quarterly Financial Information (Unaudited) - Schedule of Quarterly Information (Details)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-schedule-of-quarterly-information-details" xlink:to="bcrx_statement-statement-note-11-quarterly-financial-information-unaudited-schedule-of-quarterly-information-details-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NotesToFinancialStatements" xlink:label="bcrx_NotesToFinancialStatements" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NotesToFinancialStatements-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Notes To Financial Statements</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NotesToFinancialStatements" xlink:to="bcrx_NotesToFinancialStatements-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation, Stock Options, Activity [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NotesToFinancialStatementsAbstract" xlink:label="bcrx_NotesToFinancialStatementsAbstract" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NotesToFinancialStatementsAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Notes To Financial Statements [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NotesToFinancialStatementsAbstract" xlink:to="bcrx_NotesToFinancialStatementsAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation, Activity [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Awards available, Restricted stock awards cancelled (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sales and maturities of investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:to="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_USGovernmentAgenciesDebtSecuritiesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">US Government Agencies Debt Securities [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:to="us-gaap_USGovernmentAgenciesDebtSecuritiesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Awards available, Restricted stock awards granted (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="us-gaap_CorporateDebtSecuritiesMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CorporateDebtSecuritiesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Corporate Debt Securities [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CorporateDebtSecuritiesMember" xlink:to="us-gaap_CorporateDebtSecuritiesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CapitalLeaseObligationsCurrent" xlink:label="us-gaap_CapitalLeaseObligationsCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CapitalLeaseObligationsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CapitalLeaseObligationsCurrent</link:label>
    <link:label xlink:label="us-gaap_CapitalLeaseObligationsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lease financing obligation</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CapitalLeaseObligationsCurrent" xlink:to="us-gaap_CapitalLeaseObligationsCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAndExercisableTableTextBlock" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAndExercisableTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAndExercisableTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAndExercisableTableTextBlock" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAndExercisableTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other comprehensive income (loss)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Weighted average exercise price, ending balance (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NotesPayableCurrent" xlink:label="us-gaap_NotesPayableCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NotesPayableCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-recourse notes payable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayableCurrent" xlink:to="us-gaap_NotesPayableCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax" xlink:label="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax</link:label>
    <link:label xlink:label="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax" xlink:to="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ForeignExchangeContractMember" xlink:label="us-gaap_ForeignExchangeContractMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ForeignExchangeContractMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign Exchange Contract [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignExchangeContractMember" xlink:to="us-gaap_ForeignExchangeContractMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LinesOfCreditCurrent" xlink:label="us-gaap_LinesOfCreditCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LinesOfCreditCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LinesOfCreditCurrent</link:label>
    <link:label xlink:label="us-gaap_LinesOfCreditCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Senior credit facility</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LinesOfCreditCurrent" xlink:to="us-gaap_LinesOfCreditCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock option awards granted (in dollars per share)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock option awards vested (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock option awards forfeited (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Weighted average grant-date fair value (in dollars per share)</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Balance December 31, 2018 (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Stock option awards vested (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt</link:label>
    <link:label xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Purchases of investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:to="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount" xlink:label="bcrx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount" xlink:type="locator"/>
    <link:label xlink:label="bcrx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Orphan drug credit</link:label>
    <link:label xlink:label="bcrx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents orphan drug credit.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount" xlink:to="bcrx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Non-vested stock option awards (in shares)</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Balance December 31, 2018 (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Instruments [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Weighted average exercise price, beginning balance (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted average exercise price, stock option awards cancelled (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_FinancialInstrumentAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Instrument [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_FinancialInstrumentAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number, Ending Balance</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted average exercise price, stock option awards granted (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxesPayableCurrent" xlink:label="us-gaap_TaxesPayableCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TaxesPayableCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_TaxesPayableCurrent</link:label>
    <link:label xlink:label="us-gaap_TaxesPayableCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Duties and taxes</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxesPayableCurrent" xlink:to="us-gaap_TaxesPayableCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted average exercise price, stock option awards exercised (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="us-gaap_AccruedLiabilitiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accrued expenses</link:label>
    <link:label xlink:label="us-gaap_AccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total accrued expenses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedLiabilitiesCurrent" xlink:to="us-gaap_AccruedLiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_EmployeeRelatedLiabilitiesCurrent</link:label>
    <link:label xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Compensation and benefits</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MilestonePaymentReceived" xlink:label="bcrx_MilestonePaymentReceived" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MilestonePaymentReceived-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MilestonePaymentReceived</link:label>
    <link:label xlink:label="bcrx_MilestonePaymentReceived-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Milestone Payment Received</link:label>
    <link:label xlink:label="bcrx_MilestonePaymentReceived-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the amount of milestone payment received.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MilestonePaymentReceived" xlink:to="bcrx_MilestonePaymentReceived-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestPayableCurrent" xlink:label="us-gaap_InterestPayableCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InterestPayableCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest payable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestPayableCurrent" xlink:to="us-gaap_InterestPayableCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsPayableCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounts payable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableCurrent" xlink:to="us-gaap_AccountsPayableCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Options outstanding, beginning balance (in shares)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Options outstanding, ending balance (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromSaleOfFurnitureAndFixtures" xlink:label="us-gaap_ProceedsFromSaleOfFurnitureAndFixtures" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromSaleOfFurnitureAndFixtures-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from sale of property and equipment</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromSaleOfFurnitureAndFixtures" xlink:to="us-gaap_ProceedsFromSaleOfFurnitureAndFixtures-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Options outstanding, stock option awards cancelled (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CreditFacilityAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CreditFacilityDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_CreditFacilityDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OtherAccruedLiabilitiesCurrent</link:label>
    <link:label xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:to="us-gaap_OtherAccruedLiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PolicyTextBlockAbstract" xlink:label="us-gaap_PolicyTextBlockAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PolicyTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PolicyTextBlockAbstract</link:label>
    <link:label xlink:label="us-gaap_PolicyTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accounting Policies</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PolicyTextBlockAbstract" xlink:to="us-gaap_PolicyTextBlockAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireProductiveAssets" xlink:label="us-gaap_PaymentsToAcquireProductiveAssets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PaymentsToAcquireProductiveAssets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PaymentsToAcquireProductiveAssets</link:label>
    <link:label xlink:label="us-gaap_PaymentsToAcquireProductiveAssets-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Acquisition of property and equipment</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireProductiveAssets" xlink:to="us-gaap_PaymentsToAcquireProductiveAssets-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Awards available, beginning balance (in shares)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Awards available, ending balance (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:label="us-gaap_AccruedProfessionalFeesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccruedProfessionalFeesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AccruedProfessionalFeesCurrent</link:label>
    <link:label xlink:label="us-gaap_AccruedProfessionalFeesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Professional fees</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedProfessionalFeesCurrent" xlink:to="us-gaap_AccruedProfessionalFeesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_IncreaseDecreaseInFinancingLeaseObligations" xlink:label="bcrx_IncreaseDecreaseInFinancingLeaseObligations" xlink:type="locator"/>
    <link:label xlink:label="bcrx_IncreaseDecreaseInFinancingLeaseObligations-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">(Decrease) increase in lease financing obligation</link:label>
    <link:label xlink:label="bcrx_IncreaseDecreaseInFinancingLeaseObligations-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The increase (decrease) during the period for financing lease obligations.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_IncreaseDecreaseInFinancingLeaseObligations" xlink:to="bcrx_IncreaseDecreaseInFinancingLeaseObligations-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Awards available, plan amendment (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SeqirusUKLimitedMember" xlink:label="bcrx_SeqirusUKLimitedMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SeqirusUKLimitedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Seqirus UK Limited [Member]</link:label>
    <link:label xlink:label="bcrx_SeqirusUKLimitedMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to Seqirus UK Limited.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SeqirusUKLimitedMember" xlink:to="bcrx_SeqirusUKLimitedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">LIABILITIES AND STOCKHOLDERS&#8217; EQUITY</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VestingAxis" xlink:label="us-gaap_VestingAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_VestingAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Vesting [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VestingAxis" xlink:to="us-gaap_VestingAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VestingDomain" xlink:label="us-gaap_VestingDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_VestingDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Vesting [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VestingDomain" xlink:to="us-gaap_VestingDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProductMember" xlink:label="us-gaap_ProductMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProductMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Product [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProductMember" xlink:to="us-gaap_ProductMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_Assets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_Assets</link:label>
    <link:label xlink:label="us-gaap_Assets-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Assets" xlink:to="us-gaap_Assets-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PlanNameAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Plan Name [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PlanNameDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Plan Name [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameDomain" xlink:to="us-gaap_PlanNameDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_DesignatedForInterestOnNotesMember" xlink:label="bcrx_DesignatedForInterestOnNotesMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_DesignatedForInterestOnNotesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Designated for Interest on Notes [Member]</link:label>
    <link:label xlink:label="bcrx_DesignatedForInterestOnNotesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the restricted cash designated for interest on the notes.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_DesignatedForInterestOnNotesMember" xlink:to="bcrx_DesignatedForInterestOnNotesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized</link:label>
    <link:label xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SecuredCreditFacilityThirdTrancheMember" xlink:label="bcrx_SecuredCreditFacilityThirdTrancheMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SecuredCreditFacilityThirdTrancheMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Secured Credit Facility, Third Tranche [Member]</link:label>
    <link:label xlink:label="bcrx_SecuredCreditFacilityThirdTrancheMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represent the third tranche of a secured credit facility.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SecuredCreditFacilityThirdTrancheMember" xlink:to="bcrx_SecuredCreditFacilityThirdTrancheMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SecuredCreditFacilitySecondTrancheMember" xlink:label="bcrx_SecuredCreditFacilitySecondTrancheMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SecuredCreditFacilitySecondTrancheMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Secured Credit Facility, Second Tranche [Member]</link:label>
    <link:label xlink:label="bcrx_SecuredCreditFacilitySecondTrancheMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the second tranche of a secured credit facility.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SecuredCreditFacilitySecondTrancheMember" xlink:to="bcrx_SecuredCreditFacilitySecondTrancheMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SecuredCreditFacilityFirstTrancheMember" xlink:label="bcrx_SecuredCreditFacilityFirstTrancheMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SecuredCreditFacilityFirstTrancheMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Secured Credit Facility, First Tranche [Member]</link:label>
    <link:label xlink:label="bcrx_SecuredCreditFacilityFirstTrancheMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the first tranche of a secured credit facility.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SecuredCreditFacilityFirstTrancheMember" xlink:to="bcrx_SecuredCreditFacilityFirstTrancheMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Disclosure of Compensation Related Costs, Share-based Payments [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Award [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AwardDateAxis" xlink:label="us-gaap_AwardDateAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AwardDateAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Date [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AwardDateAxis" xlink:to="us-gaap_AwardDateAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AwardDateDomain" xlink:label="us-gaap_AwardDateDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AwardDateDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Date [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AwardDateDomain" xlink:to="us-gaap_AwardDateDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AwardTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_AwardTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net loss</link:label>
    <link:label xlink:label="us-gaap_NetIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net loss</link:label>
    <link:label xlink:label="us-gaap_NetIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net Loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_NetIncomeLoss-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="us-gaap_RestrictedStockUnitsRSUMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedStockUnitsRSUMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted Stock Units (RSUs) [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedStockUnitsRSUMember" xlink:to="us-gaap_RestrictedStockUnitsRSUMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PerformanceSharesMember" xlink:label="us-gaap_PerformanceSharesMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PerformanceSharesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Performance Shares [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PerformanceSharesMember" xlink:to="us-gaap_PerformanceSharesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AmortizationOfDiscountAndPremiumOnInvestments" xlink:label="bcrx_AmortizationOfDiscountAndPremiumOnInvestments" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AmortizationOfDiscountAndPremiumOnInvestments-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amortization of premium/discount on investments</link:label>
    <link:label xlink:label="bcrx_AmortizationOfDiscountAndPremiumOnInvestments-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Amount of amortization expense attributable to the discount and premium on investments.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AmortizationOfDiscountAndPremiumOnInvestments" xlink:to="bcrx_AmortizationOfDiscountAndPremiumOnInvestments-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EmployeeStockOptionMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Employee Stock Option [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeStockOptionMember" xlink:to="us-gaap_EmployeeStockOptionMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment</link:label>
    <link:label xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Less accumulated depreciation and amortization</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentNet-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property and equipment, net</link:label>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentNet-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Property and equipment, net</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="us-gaap_PropertyPlantAndEquipmentNet-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="us-gaap_PropertyPlantAndEquipmentGross" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentGross-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property and equipment</link:label>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentGross-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Gross, Ending Balance</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentGross" xlink:to="us-gaap_PropertyPlantAndEquipmentGross-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:label="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Calculated under Revenue Guidance in Effect before Topic 606 [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:to="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CapitalLeasesFutureMinimumPaymentsDue" xlink:label="us-gaap_CapitalLeasesFutureMinimumPaymentsDue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CapitalLeasesFutureMinimumPaymentsDue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CapitalLeasesFutureMinimumPaymentsDue</link:label>
    <link:label xlink:label="us-gaap_CapitalLeasesFutureMinimumPaymentsDue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Capital Leases, Future Minimum Payments Due, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CapitalLeasesFutureMinimumPaymentsDue" xlink:to="us-gaap_CapitalLeasesFutureMinimumPaymentsDue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_JPY" xlink:label="currency_JPY" xlink:type="locator"/>
    <link:label xlink:label="currency_JPY-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Japan, Yen</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="currency_JPY" xlink:to="currency_JPY-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments" xlink:label="us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Loss on foreign currency derivative</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments" xlink:to="us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DerivativeInstrumentRiskAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instrument [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeInstrumentRiskAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DerivativeContractTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Contract [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_DerivativeContractTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Estimated Fair Value</link:label>
    <link:label xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:label="us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInInterestPayableNet-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Interest payable</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInInterestPayableNet-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInInterestPayableNet</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:to="us-gaap_IncreaseDecreaseInInterestPayableNet-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxExpenseBenefit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncomeTaxExpenseBenefit</link:label>
    <link:label xlink:label="us-gaap_IncomeTaxExpenseBenefit-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Income tax expense</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxExpenseBenefit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Accounts payable and accrued expenses</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInAccountsPayable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsPayable" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayable-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentTerm" xlink:label="us-gaap_DebtInstrumentTerm" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtInstrumentTerm-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DebtInstrumentTerm</link:label>
    <link:label xlink:label="us-gaap_DebtInstrumentTerm-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Term</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentTerm" xlink:to="us-gaap_DebtInstrumentTerm-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount</link:label>
    <link:label xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Defined Contribution Plan, Employer Discretionary Contribution Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" xlink:to="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="currency_AllCurrenciesDomain" xlink:type="locator"/>
    <link:label xlink:label="currency_AllCurrenciesDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">All Currencies [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="currency_AllCurrenciesDomain" xlink:to="currency_AllCurrenciesDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted cash</link:label>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restricted Cash and Cash Equivalents, Current, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RoyaltyMember" xlink:label="us-gaap_RoyaltyMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RoyaltyMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Royalty [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RoyaltyMember" xlink:to="us-gaap_RoyaltyMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount" xlink:label="bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount" xlink:type="locator"/>
    <link:label xlink:label="bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount</link:label>
    <link:label xlink:label="bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Effect of ASU 2016-09</link:label>
    <link:label xlink:label="bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to the effect from the adoption of an accounting standards update.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount" xlink:to="bcrx_IncomeTaxRateReconciliationAdoptionOfAccountingStandardsUpdateAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AllocatedShareBasedCompensationExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AllocatedShareBasedCompensationExpense</link:label>
    <link:label xlink:label="us-gaap_AllocatedShareBasedCompensationExpense-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Allocated Share-based Compensation Expense, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AllocatedShareBasedCompensationExpense" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RoyaltyExpense" xlink:label="us-gaap_RoyaltyExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RoyaltyExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Royalty</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RoyaltyExpense" xlink:to="us-gaap_RoyaltyExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag" xlink:type="locator"/>
    <link:label xlink:label="dei_AmendmentFlag-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amendment Flag</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ComprehensiveIncomeNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ComprehensiveIncomeNetOfTax</link:label>
    <link:label xlink:label="us-gaap_ComprehensiveIncomeNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net comprehensive loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNetOfTax" xlink:to="us-gaap_ComprehensiveIncomeNetOfTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UseOfEstimates" xlink:label="us-gaap_UseOfEstimates" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UseOfEstimates-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Use of Estimates, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UseOfEstimates" xlink:to="us-gaap_UseOfEstimates-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized" xlink:label="bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized</link:label>
    <link:label xlink:label="bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Revenue Recognition Royalty and Milestone Revenue Recognized</link:label>
    <link:label xlink:label="bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Revenue recognition royalty and milestone revenue recognized.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized" xlink:to="bcrx_RevenueRecognitionRoyaltyAndMilestoneRevenueRecognized-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Deferred revenue</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInContractWithCustomerLiability</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:to="us-gaap_IncreaseDecreaseInContractWithCustomerLiability-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockSharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, shares outstanding (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockSharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, shares outstanding (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesOutstanding" xlink:to="us-gaap_PreferredStockSharesOutstanding-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities" xlink:label="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities</link:label>
    <link:label xlink:label="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Average Maturity Period of High Quality Marketable Securities</link:label>
    <link:label xlink:label="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Average maturity period of high quality marketable securities.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities" xlink:to="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInDerivativeAssets" xlink:label="us-gaap_IncreaseDecreaseInDerivativeAssets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInDerivativeAssets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInDerivativeAssets</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInDerivativeAssets-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Change in fair value of foreign currency derivative</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInDerivativeAssets" xlink:to="us-gaap_IncreaseDecreaseInDerivativeAssets-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MaturityperiodOfShortTermInvestment" xlink:label="bcrx_MaturityperiodOfShortTermInvestment" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MaturityperiodOfShortTermInvestment-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MaturityperiodOfShortTermInvestment</link:label>
    <link:label xlink:label="bcrx_MaturityperiodOfShortTermInvestment-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maturity Period of Short Term Investment</link:label>
    <link:label xlink:label="bcrx_MaturityperiodOfShortTermInvestment-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Maturity period of short term investment.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MaturityperiodOfShortTermInvestment" xlink:to="bcrx_MaturityperiodOfShortTermInvestment-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate" xlink:type="locator"/>
    <link:label xlink:label="dei_CurrentFiscalYearEndDate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Current Fiscal Year End Date</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CurrentFiscalYearEndDate" xlink:to="dei_CurrentFiscalYearEndDate-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DebtInstrumentBasisSpreadOnVariableRate1</link:label>
    <link:label xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Basis Spread on Variable Rate</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities" xlink:label="bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities" xlink:type="locator"/>
    <link:label xlink:label="bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities</link:label>
    <link:label xlink:label="bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Deferred collaboration expense</link:label>
    <link:label xlink:label="bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents deferred collaboration expense.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities" xlink:to="bcrx_DeferredCollaborationExpenseChangesInOperatingAssetsAndLiabilities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DebtInstrumentInterestRateStatedPercentage</link:label>
    <link:label xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Interest Rate, Stated Percentage</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="us-gaap_LeaseArrangementTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LeaseArrangementTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lease Arrangement, Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseArrangementTypeAxis" xlink:to="us-gaap_LeaseArrangementTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_CollaborativeAgreementContractValue" xlink:label="bcrx_CollaborativeAgreementContractValue" xlink:type="locator"/>
    <link:label xlink:label="bcrx_CollaborativeAgreementContractValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_CollaborativeAgreementContractValue</link:label>
    <link:label xlink:label="bcrx_CollaborativeAgreementContractValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Collaborative Agreement Contract Value</link:label>
    <link:label xlink:label="bcrx_CollaborativeAgreementContractValue-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents collaborative agreement contract value.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_CollaborativeAgreementContractValue" xlink:to="bcrx_CollaborativeAgreementContractValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="us-gaap_LeaseArrangementTypeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LeaseArrangementTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lease Arrangement, Type [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseArrangementTypeDomain" xlink:to="us-gaap_LeaseArrangementTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Prepaid expenses and other assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus" xlink:type="locator"/>
    <link:label xlink:label="dei_DocumentFiscalPeriodFocus-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Fiscal Period Focus</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalPeriodFocus" xlink:to="dei_DocumentFiscalPeriodFocus-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus" xlink:type="locator"/>
    <link:label xlink:label="dei_DocumentFiscalYearFocus-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Fiscal Year Focus</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalYearFocus" xlink:to="dei_DocumentFiscalYearFocus-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MundipharmaInternationalHoldingsLimitedMember" xlink:label="bcrx_MundipharmaInternationalHoldingsLimitedMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MundipharmaInternationalHoldingsLimitedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Mundipharma International Holdings Limited [Member]</link:label>
    <link:label xlink:label="bcrx_MundipharmaInternationalHoldingsLimitedMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to Mundipharma International Holdings Limited.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MundipharmaInternationalHoldingsLimitedMember" xlink:to="bcrx_MundipharmaInternationalHoldingsLimitedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate" xlink:type="locator"/>
    <link:label xlink:label="dei_DocumentPeriodEndDate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Period End Date</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentPeriodEndDate" xlink:to="dei_DocumentPeriodEndDate-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityEmergingGrowthCompany-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Emerging Growth Company</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityEmergingGrowthCompany" xlink:to="dei_EntityEmergingGrowthCompany-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtInstrumentFaceAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DebtInstrumentFaceAmount</link:label>
    <link:label xlink:label="us-gaap_DebtInstrumentFaceAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Face Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFaceAmount" xlink:to="us-gaap_DebtInstrumentFaceAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentType" xlink:label="dei_DocumentType" xlink:type="locator"/>
    <link:label xlink:label="dei_DocumentType-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Type</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntitySmallBusiness" xlink:label="dei_EntitySmallBusiness" xlink:type="locator"/>
    <link:label xlink:label="dei_EntitySmallBusiness-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Small Business</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntitySmallBusiness" xlink:to="dei_EntitySmallBusiness-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AverageMaturityForPortfolioInvestments" xlink:label="bcrx_AverageMaturityForPortfolioInvestments" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AverageMaturityForPortfolioInvestments-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AverageMaturityForPortfolioInvestments</link:label>
    <link:label xlink:label="bcrx_AverageMaturityForPortfolioInvestments-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Average Maturity for Portfolio Investments</link:label>
    <link:label xlink:label="bcrx_AverageMaturityForPortfolioInvestments-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Average maturity for portfolio investments during the period.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AverageMaturityForPortfolioInvestments" xlink:to="bcrx_AverageMaturityForPortfolioInvestments-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityShellCompany" xlink:label="dei_EntityShellCompany" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityShellCompany-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Shell Company</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityShellCompany" xlink:to="dei_EntityShellCompany-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentInformationLineItems" xlink:label="dei_DocumentInformationLineItems" xlink:type="locator"/>
    <link:label xlink:label="dei_DocumentInformationLineItems-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Information [Line Items]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentInformationLineItems-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentInformationTable" xlink:label="dei_DocumentInformationTable" xlink:type="locator"/>
    <link:label xlink:label="dei_DocumentInformationTable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Information [Table]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentInformationTable" xlink:to="dei_DocumentInformationTable-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityPublicFloat" xlink:label="dei_EntityPublicFloat" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityPublicFloat-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Public Float</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityPublicFloat" xlink:to="dei_EntityPublicFloat-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityFilerCategory-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Filer Category</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFilerCategory" xlink:to="dei_EntityFilerCategory-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtInstrumentAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityCurrentReportingStatus-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Current Reporting Status</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCurrentReportingStatus" xlink:to="dei_EntityCurrentReportingStatus-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtInstrumentNameDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="us-gaap_DebtInstrumentNameDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityVoluntaryFilers" xlink:label="dei_EntityVoluntaryFilers" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityVoluntaryFilers-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Voluntary Filers</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityVoluntaryFilers" xlink:to="dei_EntityVoluntaryFilers-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityWellKnownSeasonedIssuer" xlink:label="dei_EntityWellKnownSeasonedIssuer" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityWellKnownSeasonedIssuer-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Well-known Seasoned Issuer</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityWellKnownSeasonedIssuer" xlink:to="dei_EntityWellKnownSeasonedIssuer-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LondonInterbankOfferedRateLIBORMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">London Interbank Offered Rate (LIBOR) [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:to="us-gaap_LondonInterbankOfferedRateLIBORMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_USDepartmentOfHealthAndHumanServicesMember" xlink:label="bcrx_USDepartmentOfHealthAndHumanServicesMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_USDepartmentOfHealthAndHumanServicesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">US Department of Health and Human Services [Member]</link:label>
    <link:label xlink:label="bcrx_USDepartmentOfHealthAndHumanServicesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">United States department of health and human services.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_USDepartmentOfHealthAndHumanServicesMember" xlink:to="bcrx_USDepartmentOfHealthAndHumanServicesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_VariableRateDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Variable Rate [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_VariableRateDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AECOMAndIRLMember" xlink:label="bcrx_AECOMAndIRLMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AECOMAndIRLMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">AECOM and IRL [Member]</link:label>
    <link:label xlink:label="bcrx_AECOMAndIRLMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">AECOM and IRL</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AECOMAndIRLMember" xlink:to="bcrx_AECOMAndIRLMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_UABMember" xlink:label="bcrx_UABMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_UABMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">UAB [Member]</link:label>
    <link:label xlink:label="bcrx_UABMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">UAB</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_UABMember" xlink:to="bcrx_UABMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInReceivables" xlink:label="us-gaap_IncreaseDecreaseInReceivables" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInReceivables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInReceivables</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInReceivables-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Receivables</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInReceivables" xlink:to="us-gaap_IncreaseDecreaseInReceivables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_VariableRateAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Variable Rate [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="us-gaap_ConcentrationRiskPercentage1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConcentrationRiskPercentage1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ConcentrationRiskPercentage1</link:label>
    <link:label xlink:label="us-gaap_ConcentrationRiskPercentage1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Concentration Risk, Percentage</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskPercentage1" xlink:to="us-gaap_ConcentrationRiskPercentage1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue</link:label>
    <link:label xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock-based compensation expense</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_QuarterlyFinancialInformationTextBlock" xlink:label="us-gaap_QuarterlyFinancialInformationTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_QuarterlyFinancialInformationTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Quarterly Financial Information [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_QuarterlyFinancialInformationTextBlock" xlink:to="us-gaap_QuarterlyFinancialInformationTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts" xlink:label="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts</link:label>
    <link:label xlink:label="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from awards for Research and Development Contracts</link:label>
    <link:label xlink:label="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents proceeds from awards for research and development contracts.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts" xlink:to="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityCentralIndexKey-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Central Index Key</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityRegistrantName-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Registrant Name</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityDomain" xlink:to="dei_EntityDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" xlink:type="locator"/>
    <link:label xlink:label="dei_LegalEntityAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal Entity [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LegalEntityAxis" xlink:to="dei_LegalEntityAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="us-gaap_CustomerConcentrationRiskMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CustomerConcentrationRiskMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Customer Concentration Risk [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CustomerConcentrationRiskMember" xlink:to="us-gaap_CustomerConcentrationRiskMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" xlink:label="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts</link:label>
    <link:label xlink:label="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Expected Receivable From Awards for Research and Development Contracts</link:label>
    <link:label xlink:label="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents expected receivable from awards for research and development contracts.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" xlink:to="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="us-gaap_ConcentrationRiskByTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConcentrationRiskByTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskByTypeAxis" xlink:to="us-gaap_ConcentrationRiskByTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="us-gaap_ConcentrationRiskTypeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConcentrationRiskTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Type [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskTypeDomain" xlink:to="us-gaap_ConcentrationRiskTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_BaseContractMember" xlink:label="bcrx_BaseContractMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_BaseContractMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Base Contract [Member]</link:label>
    <link:label xlink:label="bcrx_BaseContractMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The base contract of ASPR/BARDA to support BCX4430 drug manufacturing.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_BaseContractMember" xlink:to="bcrx_BaseContractMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AdditionalDevelopmentOptionsMember" xlink:label="bcrx_AdditionalDevelopmentOptionsMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AdditionalDevelopmentOptionsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional Development Options [Member]</link:label>
    <link:label xlink:label="bcrx_AdditionalDevelopmentOptionsMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The additional development options that can be exercised by the Government.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AdditionalDevelopmentOptionsMember" xlink:to="bcrx_AdditionalDevelopmentOptionsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ASPRBARDAContractMember" xlink:label="bcrx_ASPRBARDAContractMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ASPRBARDAContractMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">ASPRBARDA Contract [Member]</link:label>
    <link:label xlink:label="bcrx_ASPRBARDAContractMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The potential value of the ASPR/BARDA Contract.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ASPRBARDAContractMember" xlink:to="bcrx_ASPRBARDAContractMember-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityCommonStockSharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Common Stock, Shares Outstanding (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCommonStockSharesOutstanding" xlink:to="dei_EntityCommonStockSharesOutstanding-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_GreenCrossCorporationMember" xlink:label="bcrx_GreenCrossCorporationMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_GreenCrossCorporationMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Green Cross Corporation [Member]</link:label>
    <link:label xlink:label="bcrx_GreenCrossCorporationMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents Green Cross Corporation.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_GreenCrossCorporationMember" xlink:to="bcrx_GreenCrossCorporationMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MilestonePaymentMinimum" xlink:label="bcrx_MilestonePaymentMinimum" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MilestonePaymentMinimum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MilestonePaymentMinimum</link:label>
    <link:label xlink:label="bcrx_MilestonePaymentMinimum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Milestone Payment Minimum</link:label>
    <link:label xlink:label="bcrx_MilestonePaymentMinimum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents milestone payment minimum.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MilestonePaymentMinimum" xlink:to="bcrx_MilestonePaymentMinimum-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_TransactionCosts" xlink:label="bcrx_TransactionCosts" xlink:type="locator"/>
    <link:label xlink:label="bcrx_TransactionCosts-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_TransactionCosts</link:label>
    <link:label xlink:label="bcrx_TransactionCosts-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Transaction Costs</link:label>
    <link:label xlink:label="bcrx_TransactionCosts-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents transaction costs associated with royalty monetization.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_TransactionCosts" xlink:to="bcrx_TransactionCosts-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_InterestReserve" xlink:label="bcrx_InterestReserve" xlink:type="locator"/>
    <link:label xlink:label="bcrx_InterestReserve-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_InterestReserve</link:label>
    <link:label xlink:label="bcrx_InterestReserve-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Reserve</link:label>
    <link:label xlink:label="bcrx_InterestReserve-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents interest reserve established as part of the royalty monetization.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_InterestReserve" xlink:to="bcrx_InterestReserve-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RequiredForeignCurrencyHedgePerDollar" xlink:label="bcrx_RequiredForeignCurrencyHedgePerDollar" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RequiredForeignCurrencyHedgePerDollar-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_RequiredForeignCurrencyHedgePerDollar</link:label>
    <link:label xlink:label="bcrx_RequiredForeignCurrencyHedgePerDollar-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Required Foreign Currency Hedge Per Dollar</link:label>
    <link:label xlink:label="bcrx_RequiredForeignCurrencyHedgePerDollar-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The Company is required to maintain a foreign currency hedge per dollar under the agreements governing the PhaRMA Notes.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RequiredForeignCurrencyHedgePerDollar" xlink:to="bcrx_RequiredForeignCurrencyHedgePerDollar-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MilestonePaymentMaximum" xlink:label="bcrx_MilestonePaymentMaximum" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MilestonePaymentMaximum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MilestonePaymentMaximum</link:label>
    <link:label xlink:label="bcrx_MilestonePaymentMaximum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Milestone Payment Maximum</link:label>
    <link:label xlink:label="bcrx_MilestonePaymentMaximum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents milestone payment maximum.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MilestonePaymentMaximum" xlink:to="bcrx_MilestonePaymentMaximum-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SalesRevenueProductLineMember" xlink:label="us-gaap_SalesRevenueProductLineMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SalesRevenueProductLineMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sales Revenue, Product Line [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SalesRevenueProductLineMember" xlink:to="us-gaap_SalesRevenueProductLineMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RoyaltyMonetizationMember" xlink:label="bcrx_RoyaltyMonetizationMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RoyaltyMonetizationMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Royalty Monetization [Member]</link:label>
    <link:label xlink:label="bcrx_RoyaltyMonetizationMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the royalty monetization transaction.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RoyaltyMonetizationMember" xlink:to="bcrx_RoyaltyMonetizationMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember" xlink:label="bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">National Institute of Allergy and Infectious Diseases [Member]</link:label>
    <link:label xlink:label="bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents National Institute of Allergy and Infectious Diseases.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember" xlink:to="bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInInventories" xlink:label="us-gaap_IncreaseDecreaseInInventories" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInInventories-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInInventories</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInInventories-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Inventory</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInInventories" xlink:to="us-gaap_IncreaseDecreaseInInventories-label" xlink:type="arc"/>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol" xlink:type="locator"/>
    <link:label xlink:label="dei_TradingSymbol-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Symbol</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Benchmark [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="us-gaap_ConcentrationRiskByBenchmarkAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Benchmark [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:to="us-gaap_ConcentrationRiskBenchmarkDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Employee stock purchase plan sales, shares (in shares)</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, Employee Stock Purchase Plans</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:to="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd</link:label>
    <link:label xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Interest Rate at Period End</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:to="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise of stock options, shares (in shares)</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Options outstanding, stock option awards exercised (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TableTextBlock" xlink:label="us-gaap_TableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_TableTextBlock</link:label>
    <link:label xlink:label="us-gaap_TableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Notes Tables</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TableTextBlock" xlink:to="us-gaap_TableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_CurrencyHedgeAgreementMember" xlink:label="bcrx_CurrencyHedgeAgreementMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_CurrencyHedgeAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Currency Hedge Agreement [Member]</link:label>
    <link:label xlink:label="bcrx_CurrencyHedgeAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the Currency Hedge Agreement to hedge certain risks associated with changes in the value of the Japanese yen relative to the U.S. dollar.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_CurrencyHedgeAgreementMember" xlink:to="bcrx_CurrencyHedgeAgreementMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MaximumAggregateOfferingPrice" xlink:label="bcrx_MaximumAggregateOfferingPrice" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MaximumAggregateOfferingPrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MaximumAggregateOfferingPrice</link:label>
    <link:label xlink:label="bcrx_MaximumAggregateOfferingPrice-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maximum Aggregate Offering Price</link:label>
    <link:label xlink:label="bcrx_MaximumAggregateOfferingPrice-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the maximum aggregate offering price of common stock, preferred stock, depository shares, stock purchase contracts, warrants and units.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MaximumAggregateOfferingPrice" xlink:to="bcrx_MaximumAggregateOfferingPrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee stock purchase plan sales</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:to="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GainLossOnDispositionOfAssets1" xlink:label="us-gaap_GainLossOnDispositionOfAssets1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_GainLossOnDispositionOfAssets1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_GainLossOnDispositionOfAssets1</link:label>
    <link:label xlink:label="us-gaap_GainLossOnDispositionOfAssets1-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Loss (gain) on disposal of property and equipment</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GainLossOnDispositionOfAssets1" xlink:to="us-gaap_GainLossOnDispositionOfAssets1-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AnnualLicenseFeeMinimum" xlink:label="bcrx_AnnualLicenseFeeMinimum" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AnnualLicenseFeeMinimum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AnnualLicenseFeeMinimum</link:label>
    <link:label xlink:label="bcrx_AnnualLicenseFeeMinimum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Annual License Fee Minimum</link:label>
    <link:label xlink:label="bcrx_AnnualLicenseFeeMinimum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represent minimum annual license fee.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AnnualLicenseFeeMinimum" xlink:to="bcrx_AnnualLicenseFeeMinimum-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Exercise of stock options</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AnnualLicenseFeeMaximum" xlink:label="bcrx_AnnualLicenseFeeMaximum" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AnnualLicenseFeeMaximum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AnnualLicenseFeeMaximum</link:label>
    <link:label xlink:label="bcrx_AnnualLicenseFeeMaximum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Annual License Fee Maximum</link:label>
    <link:label xlink:label="bcrx_AnnualLicenseFeeMaximum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents annual maximum license fee.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AnnualLicenseFeeMaximum" xlink:to="bcrx_AnnualLicenseFeeMaximum-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LossOnSaleOfInvestments" xlink:label="us-gaap_LossOnSaleOfInvestments" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LossOnSaleOfInvestments-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LossOnSaleOfInvestments</link:label>
    <link:label xlink:label="us-gaap_LossOnSaleOfInvestments-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Loss on Sale of Investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossOnSaleOfInvestments" xlink:to="us-gaap_LossOnSaleOfInvestments-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Selling, general and administrative</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SellingGeneralAndAdministrativeExpense" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NumberOfStockbasedCompensationPlans" xlink:label="bcrx_NumberOfStockbasedCompensationPlans" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NumberOfStockbasedCompensationPlans-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_NumberOfStockbasedCompensationPlans</link:label>
    <link:label xlink:label="bcrx_NumberOfStockbasedCompensationPlans-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of Stock-based Compensation Plans</link:label>
    <link:label xlink:label="bcrx_NumberOfStockbasedCompensationPlans-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents number of stock based compensation plan.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NumberOfStockbasedCompensationPlans" xlink:to="bcrx_NumberOfStockbasedCompensationPlans-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock option awards granted (in shares)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Stock option awards forfeited (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Options outstanding, stock option awards granted (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="us-gaap_LineOfCreditFacilityLenderDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCreditFacilityLenderDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Lender [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityLenderDomain" xlink:to="us-gaap_LineOfCreditFacilityLenderDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Arrangements and Non-arrangement Transactions [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage" xlink:label="bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage</link:label>
    <link:label xlink:label="bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Shar-based Payment Award, Awards Unvested, Percentage</link:label>
    <link:label xlink:label="bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the percentage of performance awards that remain unvested.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage" xlink:to="bcrx_SharebasedCompensationArrangementBySharbasedPaymentAwardAwardsUnvestedPercentage-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Issuance of common stock, shares (in shares)</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, New Issues</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AdvanceNoticePeriodForTerminationOfAgreement" xlink:label="bcrx_AdvanceNoticePeriodForTerminationOfAgreement" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AdvanceNoticePeriodForTerminationOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AdvanceNoticePeriodForTerminationOfAgreement</link:label>
    <link:label xlink:label="bcrx_AdvanceNoticePeriodForTerminationOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Advance Notice Period for Termination of Agreement</link:label>
    <link:label xlink:label="bcrx_AdvanceNoticePeriodForTerminationOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents advance notice period for termination of agreement.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AdvanceNoticePeriodForTerminationOfAgreement" xlink:to="bcrx_AdvanceNoticePeriodForTerminationOfAgreement-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="us-gaap_LineOfCreditFacilityAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCreditFacilityAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lender Name [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityAxis" xlink:to="us-gaap_LineOfCreditFacilityAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum" xlink:label="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum</link:label>
    <link:label xlink:label="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of Salary to Purchase Common Stock, Maximum</link:label>
    <link:label xlink:label="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents percentage of salary to purchase common stock maximum.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum" xlink:to="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PercentageOfCommonStockSharesBeginning" xlink:label="bcrx_PercentageOfCommonStockSharesBeginning" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PercentageOfCommonStockSharesBeginning-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PercentageOfCommonStockSharesBeginning</link:label>
    <link:label xlink:label="bcrx_PercentageOfCommonStockSharesBeginning-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of Common Stock Shares, Beginning</link:label>
    <link:label xlink:label="bcrx_PercentageOfCommonStockSharesBeginning-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents percentage of common stock shares beginning.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PercentageOfCommonStockSharesBeginning" xlink:to="bcrx_PercentageOfCommonStockSharesBeginning-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LiabilitiesAndStockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LiabilitiesAndStockholdersEquity</link:label>
    <link:label xlink:label="us-gaap_LiabilitiesAndStockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total liabilities and stockholders&#8217; equity</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PercentageOfCommonStockSharesEnding" xlink:label="bcrx_PercentageOfCommonStockSharesEnding" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PercentageOfCommonStockSharesEnding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PercentageOfCommonStockSharesEnding</link:label>
    <link:label xlink:label="bcrx_PercentageOfCommonStockSharesEnding-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of Common Stock Shares, Ending</link:label>
    <link:label xlink:label="bcrx_PercentageOfCommonStockSharesEnding-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents percentage of common stock shares ending.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PercentageOfCommonStockSharesEnding" xlink:to="bcrx_PercentageOfCommonStockSharesEnding-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Issuance of common stock</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" xlink:label="bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount</link:label>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shar-based Compensation Arrangement by Shar-based Payment Award, Maximum Number of Shares Per Employee, Amount</link:label>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents share-based compensation arrangement by share-based payment award maximum value per employee amount.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" xlink:to="bcrx_ShareBasedCompensationArrangementBySharbasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accumulated deficit</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="us-gaap_ResearchAndDevelopmentExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchAndDevelopmentExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research and development</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpense" xlink:to="us-gaap_ResearchAndDevelopmentExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accumulated other comprehensive loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtDisclosureTextBlock" xlink:label="us-gaap_DebtDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureTextBlock" xlink:to="us-gaap_DebtDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InterestExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_InterestExpense</link:label>
    <link:label xlink:label="us-gaap_InterestExpense-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Expense, Total</link:label>
    <link:label xlink:label="us-gaap_InterestExpense-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Interest expense</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpense" xlink:to="us-gaap_InterestExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InterestExpenseDebt-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_InterestExpenseDebt</link:label>
    <link:label xlink:label="us-gaap_InterestExpenseDebt-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Expense, Debt, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebt" xlink:to="us-gaap_InterestExpenseDebt-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PeriodOfAgreement" xlink:label="bcrx_PeriodOfAgreement" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PeriodOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PeriodOfAgreement</link:label>
    <link:label xlink:label="bcrx_PeriodOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Period of Agreement</link:label>
    <link:label xlink:label="bcrx_PeriodOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents period of agreement.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PeriodOfAgreement" xlink:to="bcrx_PeriodOfAgreement-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Changes in operating assets and liabilities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RenewablePeriodOfAgreement" xlink:label="bcrx_RenewablePeriodOfAgreement" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RenewablePeriodOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_RenewablePeriodOfAgreement</link:label>
    <link:label xlink:label="bcrx_RenewablePeriodOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Renewable Period of Agreement</link:label>
    <link:label xlink:label="bcrx_RenewablePeriodOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents renewable period of agreement.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RenewablePeriodOfAgreement" xlink:to="bcrx_RenewablePeriodOfAgreement-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AmortizationOfFinancingCosts-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amortization of debt issuance costs</link:label>
    <link:label xlink:label="us-gaap_AmortizationOfFinancingCosts-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amortization of Debt Issuance Costs</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfFinancingCosts" xlink:to="us-gaap_AmortizationOfFinancingCosts-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted Cash and Cash Equivalents [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NotesPayableFairValueDisclosure" xlink:label="us-gaap_NotesPayableFairValueDisclosure" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NotesPayableFairValueDisclosure-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NotesPayableFairValueDisclosure</link:label>
    <link:label xlink:label="us-gaap_NotesPayableFairValueDisclosure-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Notes Payable, Fair Value Disclosure</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayableFairValueDisclosure" xlink:to="us-gaap_NotesPayableFairValueDisclosure-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DisclosureTextBlockAbstract" xlink:label="us-gaap_DisclosureTextBlockAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DisclosureTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DisclosureTextBlockAbstract</link:label>
    <link:label xlink:label="us-gaap_DisclosureTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Notes to Financial Statements</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_DisclosureTextBlockAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_IncentivePlanMember" xlink:label="bcrx_IncentivePlanMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_IncentivePlanMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Incentive Plan [Member]</link:label>
    <link:label xlink:label="bcrx_IncentivePlanMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents Incentive Plan.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_IncentivePlanMember" xlink:to="bcrx_IncentivePlanMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_EmployeeStockPurchasePlanMember" xlink:label="bcrx_EmployeeStockPurchasePlanMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_EmployeeStockPurchasePlanMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Employee Stock Purchase Plan [Member]</link:label>
    <link:label xlink:label="bcrx_EmployeeStockPurchasePlanMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Employee stock purchase plan, (ESPP).</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_EmployeeStockPurchasePlanMember" xlink:to="bcrx_EmployeeStockPurchasePlanMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SubsequentEventMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventMember" xlink:to="us-gaap_SubsequentEventMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RoyaltyMonetizationTextBlock" xlink:label="bcrx_RoyaltyMonetizationTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RoyaltyMonetizationTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Royalty Monetization [Text Block]</link:label>
    <link:label xlink:label="bcrx_RoyaltyMonetizationTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Royalty monetization.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RoyaltyMonetizationTextBlock" xlink:to="bcrx_RoyaltyMonetizationTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="us-gaap_OperatingLeaseLiability" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeaseLiability-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeaseLiability</link:label>
    <link:label xlink:label="us-gaap_OperatingLeaseLiability-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating Lease, Liability, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiability" xlink:to="us-gaap_OperatingLeaseLiability-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SubsequentEventTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SubsequentEventTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event Type [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pension and Other Postretirement Benefits Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock" xlink:to="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NonEmployeeDirectorsMember" xlink:label="bcrx_NonEmployeeDirectorsMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NonEmployeeDirectorsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-employee Directors [Member]</link:label>
    <link:label xlink:label="bcrx_NonEmployeeDirectorsMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents non-employee directors of the company.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NonEmployeeDirectorsMember" xlink:to="bcrx_NonEmployeeDirectorsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventsTextBlock" xlink:label="us-gaap_SubsequentEventsTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SubsequentEventsTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Events [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsTextBlock" xlink:to="us-gaap_SubsequentEventsTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeaseRightOfUseAsset-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeaseRightOfUseAsset</link:label>
    <link:label xlink:label="us-gaap_OperatingLeaseRightOfUseAsset-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating Lease, Right-of-Use Asset</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable" xlink:label="bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Awards available, stock option awards cancelled (in shares)</link:label>
    <link:label xlink:label="bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Share based compensation arrangement by share based payment award options forfeitures in period awards available.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable" xlink:to="bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AvailableForSaleSecuritiesDebtMaturitiesMaturingAfterTwoYears" xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesMaturingAfterTwoYears" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesMaturingAfterTwoYears-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Maturing after two years</link:label>
    <link:label xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesMaturingAfterTwoYears-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents debt maturities after two years.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AvailableForSaleSecuritiesDebtMaturitiesMaturingAfterTwoYears" xlink:to="bcrx_AvailableForSaleSecuritiesDebtMaturitiesMaturingAfterTwoYears-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Securities, Available-for-sale [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PrivatePlacementOfSeniorSecuredNotes" xlink:label="bcrx_PrivatePlacementOfSeniorSecuredNotes" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PrivatePlacementOfSeniorSecuredNotes-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PrivatePlacementOfSeniorSecuredNotes</link:label>
    <link:label xlink:label="bcrx_PrivatePlacementOfSeniorSecuredNotes-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Private Placement of Senior Secured Notes</link:label>
    <link:label xlink:label="bcrx_PrivatePlacementOfSeniorSecuredNotes-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents private placement of senior secured notes.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PrivatePlacementOfSeniorSecuredNotes" xlink:to="bcrx_PrivatePlacementOfSeniorSecuredNotes-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="us-gaap_OtherAssetsNoncurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherAssetsNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsNoncurrent" xlink:to="us-gaap_OtherAssetsNoncurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="us-gaap_ShareBasedCompensation" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensation-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock-based compensation expense</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensation" xlink:to="us-gaap_ShareBasedCompensation-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeLeasesPolicyTextBlock" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LesseeLeasesPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lessee, Leases [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeLeasesPolicyTextBlock" xlink:to="us-gaap_LesseeLeasesPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:label="us-gaap_TitleOfIndividualAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TitleOfIndividualAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Title of Individual [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TitleOfIndividualAxis" xlink:to="us-gaap_TitleOfIndividualAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Relationship to Entity [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:to="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerSharePolicyTextBlock" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EarningsPerSharePolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerSharePolicyTextBlock" xlink:to="us-gaap_EarningsPerSharePolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_LongtermInvestmentMaturityMinimum" xlink:label="bcrx_LongtermInvestmentMaturityMinimum" xlink:type="locator"/>
    <link:label xlink:label="bcrx_LongtermInvestmentMaturityMinimum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_LongtermInvestmentMaturityMinimum</link:label>
    <link:label xlink:label="bcrx_LongtermInvestmentMaturityMinimum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term Investment Maturity, Minimum</link:label>
    <link:label xlink:label="bcrx_LongtermInvestmentMaturityMinimum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents long term investment maturity minimum.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_LongtermInvestmentMaturityMinimum" xlink:to="bcrx_LongtermInvestmentMaturityMinimum-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomePolicyPolicyTextBlock" xlink:label="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Comprehensive Income, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock" xlink:to="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxPolicyTextBlock" xlink:label="us-gaap_IncomeTaxPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxPolicyTextBlock" xlink:to="us-gaap_IncomeTaxPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MaximumAmountOfCollateralRequiredToPost" xlink:label="bcrx_MaximumAmountOfCollateralRequiredToPost" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MaximumAmountOfCollateralRequiredToPost-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MaximumAmountOfCollateralRequiredToPost</link:label>
    <link:label xlink:label="bcrx_MaximumAmountOfCollateralRequiredToPost-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maximum Amount of Collateral Required to Post</link:label>
    <link:label xlink:label="bcrx_MaximumAmountOfCollateralRequiredToPost-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents maximum amount of collateral required to post.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MaximumAmountOfCollateralRequiredToPost" xlink:to="bcrx_MaximumAmountOfCollateralRequiredToPost-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_JPRRoyaltySubLLCMember" xlink:label="bcrx_JPRRoyaltySubLLCMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_JPRRoyaltySubLLCMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">JPR Royalty Sub LLC [Member]</link:label>
    <link:label xlink:label="bcrx_JPRRoyaltySubLLCMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents JPR Royalty Sub LLC.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_JPRRoyaltySubLLCMember" xlink:to="bcrx_JPRRoyaltySubLLCMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PhaRMANotesMember" xlink:label="bcrx_PhaRMANotesMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PhaRMANotesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">PhaRMA Notes Member]</link:label>
    <link:label xlink:label="bcrx_PhaRMANotesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents PhaRMA notes.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PhaRMANotesMember" xlink:to="bcrx_PhaRMANotesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_CollateralForCreditMember" xlink:label="bcrx_CollateralForCreditMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_CollateralForCreditMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Collateral for Credit [Member]</link:label>
    <link:label xlink:label="bcrx_CollateralForCreditMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Restricted cash and cash equivalents required to maintain as collateral for a letter of credit.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_CollateralForCreditMember" xlink:to="bcrx_CollateralForCreditMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research and Development Expense, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:to="us-gaap_ResearchAndDevelopmentExpensePolicy-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RAPIVABMember" xlink:label="bcrx_RAPIVABMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RAPIVABMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">RAPIVAB [Member]</link:label>
    <link:label xlink:label="bcrx_RAPIVABMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents RAPIVAB product.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RAPIVABMember" xlink:to="bcrx_RAPIVABMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent</link:label>
    <link:label xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DepreciationDepletionAndAmortization-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Depreciation and amortization</link:label>
    <link:label xlink:label="us-gaap_DepreciationDepletionAndAmortization-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Depreciation, Depletion and Amortization, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepreciationDepletionAndAmortization" xlink:to="us-gaap_DepreciationDepletionAndAmortization-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharesIssuedPricePerShare-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharesIssuedPricePerShare</link:label>
    <link:label xlink:label="us-gaap_SharesIssuedPricePerShare-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shares Issued, Price Per Share</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesIssuedPricePerShare" xlink:to="us-gaap_SharesIssuedPricePerShare-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AssetsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AssetsCurrent</link:label>
    <link:label xlink:label="us-gaap_AssetsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total current assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrent" xlink:to="us-gaap_AssetsCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:to="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stockholders' Equity Note Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:to="us-gaap_StockholdersEquityNoteDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MaturityPeriodOfHighQualityMarketablesecurities" xlink:label="bcrx_MaturityPeriodOfHighQualityMarketablesecurities" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MaturityPeriodOfHighQualityMarketablesecurities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_MaturityPeriodOfHighQualityMarketablesecurities</link:label>
    <link:label xlink:label="bcrx_MaturityPeriodOfHighQualityMarketablesecurities-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maturity Period of High Quality Marketable Securities</link:label>
    <link:label xlink:label="bcrx_MaturityPeriodOfHighQualityMarketablesecurities-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents maturity period of high quality marketable securities.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MaturityPeriodOfHighQualityMarketablesecurities" xlink:to="bcrx_MaturityPeriodOfHighQualityMarketablesecurities-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AvailableForSaleDebtSecuritiesAccruedInterest" xlink:label="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accrued Interest</link:label>
    <link:label xlink:label="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the amount of accrued interest in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest" xlink:to="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, $0.01 par value; shares authorized &#8212; 200,000; shares issued and outstanding &#8212; 110,063 at December 31, 2018 and 98,411 at December 31, 2017</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustments to reconcile net loss to net cash used in operating activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, shares authorized (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockSharesIssued-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, shares issued (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="us-gaap_CertificatesOfDepositMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CertificatesOfDepositMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Certificates of Deposit [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CertificatesOfDepositMember" xlink:to="us-gaap_CertificatesOfDepositMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockParOrStatedValuePerShare-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, par value (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredCostsCurrent" xlink:label="us-gaap_DeferredCostsCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredCostsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred collaboration expense</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredCostsCurrent" xlink:to="us-gaap_DeferredCostsCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxAssetsValuationAllowance</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Valuation allowance</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsValuationAllowance" xlink:to="us-gaap_DeferredTaxAssetsValuationAllowance-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeMember" xlink:label="srt_RangeMember" xlink:type="locator"/>
    <link:label xlink:label="srt_RangeMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Range [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeMember" xlink:to="srt_RangeMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember" xlink:type="locator"/>
    <link:label xlink:label="srt_MaximumMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Maximum [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AvailableForSaleSecuritiesDebtMaturitiesFairValueTableTextBlock" xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesFairValueTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesFairValueTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Available For Sale Securities Debt Maturities Fair Value [Table Text Block]</link:label>
    <link:label xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesFairValueTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Tabular disclosure of available for sale securities debt maturities fair value.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AvailableForSaleSecuritiesDebtMaturitiesFairValueTableTextBlock" xlink:to="bcrx_AvailableForSaleSecuritiesDebtMaturitiesFairValueTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember" xlink:type="locator"/>
    <link:label xlink:label="srt_MinimumMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Minimum [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Maturing after one year through two years</link:label>
    <link:label xlink:label="bcrx_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents available for sale securities debt maturities after one through two years fair value.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" xlink:to="bcrx_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="srt_ProductOrServiceAxis" xlink:type="locator"/>
    <link:label xlink:label="srt_ProductOrServiceAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Product and Service [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductOrServiceAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock" xlink:label="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Receivables from Collaborations [Table Text Block]</link:label>
    <link:label xlink:label="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Tabular disclosure representing receivables from collaborations.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock" xlink:to="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="srt_ProductsAndServicesDomain" xlink:type="locator"/>
    <link:label xlink:label="srt_ProductsAndServicesDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Product and Service [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ProductsAndServicesDomain" xlink:to="srt_ProductsAndServicesDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis" xlink:type="locator"/>
    <link:label xlink:label="srt_RangeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Range [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesRentExpenseNet" xlink:label="us-gaap_OperatingLeasesRentExpenseNet" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesRentExpenseNet-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesRentExpenseNet</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesRentExpenseNet-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating Leases, Rent Expense, Net, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesRentExpenseNet" xlink:to="us-gaap_OperatingLeasesRentExpenseNet-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ShionogiAndCoLtdMember" xlink:label="bcrx_ShionogiAndCoLtdMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ShionogiAndCoLtdMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Shionogi and Co. Ltd [Member]</link:label>
    <link:label xlink:label="bcrx_ShionogiAndCoLtdMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Shionogi &amp; Co. Ltd.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ShionogiAndCoLtdMember" xlink:to="bcrx_ShionogiAndCoLtdMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, $0.001 par value; shares authorized &#8212; 5,000; no shares outstanding</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValue" xlink:to="us-gaap_PreferredStockValue-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_CSLLimitedMember" xlink:label="bcrx_CSLLimitedMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_CSLLimitedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">CSL Limited [Member</link:label>
    <link:label xlink:label="bcrx_CSLLimitedMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents CSL Limited which is a company organized under the laws of Australia.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_CSLLimitedMember" xlink:to="bcrx_CSLLimitedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxAssetsLiabilitiesNet</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net deferred tax assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:to="us-gaap_DeferredTaxAssetsLiabilitiesNet-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockSharesIssued-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, shares issued (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesIssued" xlink:to="us-gaap_PreferredStockSharesIssued-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IntangibleAssetsFiniteLivedPolicy" xlink:label="us-gaap_IntangibleAssetsFiniteLivedPolicy" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IntangibleAssetsFiniteLivedPolicy-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Intangible Assets, Finite-Lived, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IntangibleAssetsFiniteLivedPolicy" xlink:to="us-gaap_IntangibleAssetsFiniteLivedPolicy-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsOther" xlink:label="us-gaap_DeferredTaxAssetsOther" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsOther-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsOther" xlink:to="us-gaap_DeferredTaxAssetsOther-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsGross" xlink:label="us-gaap_DeferredTaxAssetsGross" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsGross-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxAssetsGross</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsGross-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total deferred tax assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsGross-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, shares authorized (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesAuthorized" xlink:to="us-gaap_PreferredStockSharesAuthorized-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilities" xlink:label="us-gaap_DeferredIncomeTaxLiabilities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredIncomeTaxLiabilities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredIncomeTaxLiabilities</link:label>
    <link:label xlink:label="us-gaap_DeferredIncomeTaxLiabilities-label" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:type="resource" xml:lang="en-US">Total deferred tax liabilities</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxLiabilities" xlink:to="us-gaap_DeferredIncomeTaxLiabilities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InventoryNet" xlink:label="us-gaap_InventoryNet" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InventoryNet-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Inventory</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryNet" xlink:to="us-gaap_InventoryNet-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, par value (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_RoyaltyTerm" xlink:label="bcrx_RoyaltyTerm" xlink:type="locator"/>
    <link:label xlink:label="bcrx_RoyaltyTerm-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_RoyaltyTerm</link:label>
    <link:label xlink:label="bcrx_RoyaltyTerm-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Royalty Term</link:label>
    <link:label xlink:label="bcrx_RoyaltyTerm-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Period of time between the date of the Agreement and its expiration.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_RoyaltyTerm" xlink:to="bcrx_RoyaltyTerm-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenues</link:label>
    <link:label xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Revenues</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:to="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsDeferredIncome" xlink:label="us-gaap_DeferredTaxAssetsDeferredIncome" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsDeferredIncome-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxAssetsDeferredIncome</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsDeferredIncome-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred revenue</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsDeferredIncome" xlink:to="us-gaap_DeferredTaxAssetsDeferredIncome-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Hierarchy and NAV [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CurrencyAxis" xlink:label="srt_CurrencyAxis" xlink:type="locator"/>
    <link:label xlink:label="srt_CurrencyAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Currency [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CurrencyAxis" xlink:to="srt_CurrencyAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MajorCustomersAxis" xlink:label="srt_MajorCustomersAxis" xlink:type="locator"/>
    <link:label xlink:label="srt_MajorCustomersAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Customer [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MajorCustomersAxis" xlink:to="srt_MajorCustomersAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="srt_NameOfMajorCustomerDomain" xlink:type="locator"/>
    <link:label xlink:label="srt_NameOfMajorCustomerDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Customer [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_NameOfMajorCustomerDomain" xlink:to="srt_NameOfMajorCustomerDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_FairValueInputsLevel2Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Inputs, Level 2 [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueInputsLevel2Member" xlink:to="us-gaap_FairValueInputsLevel2Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Hierarchy and NAV [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromLicenseFeesReceived" xlink:label="us-gaap_ProceedsFromLicenseFeesReceived" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromLicenseFeesReceived-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ProceedsFromLicenseFeesReceived</link:label>
    <link:label xlink:label="us-gaap_ProceedsFromLicenseFeesReceived-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from License Fees Received</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLicenseFeesReceived" xlink:to="us-gaap_ProceedsFromLicenseFeesReceived-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReceivablesNetCurrent" xlink:label="us-gaap_ReceivablesNetCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ReceivablesNetCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Receivables</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReceivablesNetCurrent" xlink:to="us-gaap_ReceivablesNetCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PropertyPlantAndEquipmentUsefulLife</link:label>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Useful Life</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:to="us-gaap_PropertyPlantAndEquipmentUsefulLife-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable" xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable</link:label>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Awards available, stock option awards granted (in shares)</link:label>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents share based compensation arrangement by share based payment award options grants in period awards available.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable" xlink:to="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueRecognitionPolicyTextBlock" xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenue Recognition, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRecognitionPolicyTextBlock" xlink:to="us-gaap_RevenueRecognitionPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementLineItems-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Line Items]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementLineItems-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="us-gaap_FurnitureAndFixturesMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_FurnitureAndFixturesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Furniture and Fixtures [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FurnitureAndFixturesMember" xlink:to="us-gaap_FurnitureAndFixturesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="us-gaap_AccountsReceivableNetCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsReceivableNetCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Receivables from collaborations</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsReceivableNetCurrent" xlink:to="us-gaap_AccountsReceivableNetCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="us-gaap_AdditionalPaidInCapital" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdditionalPaidInCapital-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional paid-in capital</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapital" xlink:to="us-gaap_AdditionalPaidInCapital-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock-based compensation</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BuildingMember" xlink:label="us-gaap_BuildingMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_BuildingMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Building [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BuildingMember" xlink:to="us-gaap_BuildingMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenuesAbstract" xlink:label="us-gaap_RevenuesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RevenuesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenues:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenuesAbstract" xlink:to="us-gaap_RevenuesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">AOCI Attributable to Parent [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockholdersEquityAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stockholders&#8217; equity:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="us-gaap_LeaseholdImprovementsMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LeaseholdImprovementsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Leasehold Improvements [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseholdImprovementsMember" xlink:to="us-gaap_LeaseholdImprovementsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentByTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Type [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxAssetsOperatingLossCarryforwards</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred Tax Assets, Operating Loss Carryforwards, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" xlink:to="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:label="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research and development credits</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:to="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_DescriptionOfCompanyPolicyTextBlock" xlink:label="bcrx_DescriptionOfCompanyPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_DescriptionOfCompanyPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Description of Company [Policy Text Block]</link:label>
    <link:label xlink:label="bcrx_DescriptionOfCompanyPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The description of company policy.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_DescriptionOfCompanyPolicyTextBlock" xlink:to="bcrx_DescriptionOfCompanyPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations</link:label>
    <link:label xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Cash, cash equivalents and restricted cash at beginning of year</link:label>
    <link:label xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Cash, cash equivalents and restricted cash at end of year</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net federal and state operating losses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" xlink:to="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InventoryPolicyTextBlock" xlink:label="us-gaap_InventoryPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InventoryPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Inventory, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryPolicyTextBlock" xlink:to="us-gaap_InventoryPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AssetsAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">ASSETS</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_AssetsAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect</link:label>
    <link:label xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">(Decrease) increase in cash, cash equivalents and restricted cash</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountingStandardsUpdate201609Member" xlink:label="us-gaap_AccountingStandardsUpdate201609Member" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountingStandardsUpdate201609Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounting Standards Update 2016-09 [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingStandardsUpdate201609Member" xlink:to="us-gaap_AccountingStandardsUpdate201609Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetCashProvidedByUsedInFinancingActivities</link:label>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash provided by financing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AccruedExpensesPolicyTextBlock" xlink:label="bcrx_AccruedExpensesPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AccruedExpensesPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accrued Expenses [Policy Text Block]</link:label>
    <link:label xlink:label="bcrx_AccruedExpensesPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents accrued expenses policy.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AccruedExpensesPolicyTextBlock" xlink:to="bcrx_AccruedExpensesPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" xlink:label="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Expense and Deferred Financing Costs [Policy Text Block]</link:label>
    <link:label xlink:label="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents interest expense and deferred financing costs.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" xlink:to="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_CurrencyHedgeAgreementPolicyTextBlock" xlink:label="bcrx_CurrencyHedgeAgreementPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_CurrencyHedgeAgreementPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Currency Hedge Agreement [Policy Text Block]</link:label>
    <link:label xlink:label="bcrx_CurrencyHedgeAgreementPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents currency hedge agreement policy.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_CurrencyHedgeAgreementPolicyTextBlock" xlink:to="bcrx_CurrencyHedgeAgreementPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingIncomeLoss</link:label>
    <link:label xlink:label="us-gaap_OperatingIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Loss from operations</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_OperatingIncomeLoss-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetCashProvidedByUsedInOperatingActivities</link:label>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash used in operating activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ConcentrationOfMarketRiskPolicyTextBlock" xlink:label="bcrx_ConcentrationOfMarketRiskPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ConcentrationOfMarketRiskPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration of Market Risk [Policy Text Block]</link:label>
    <link:label xlink:label="bcrx_ConcentrationOfMarketRiskPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents concentration of market risk policy.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ConcentrationOfMarketRiskPolicyTextBlock" xlink:to="bcrx_ConcentrationOfMarketRiskPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Prepaid expenses and other current assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:to="us-gaap_PrepaidExpenseAndOtherAssetsCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetCashProvidedByUsedInInvestingActivities</link:label>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash provided by (used in) investing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:label="us-gaap_CostOfGoodsAndServicesSold" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CostOfGoodsAndServicesSold-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cost of products sold</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostOfGoodsAndServicesSold" xlink:to="us-gaap_CostOfGoodsAndServicesSold-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" xlink:type="locator"/>
    <link:label xlink:label="srt_CounterpartyNameAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Counterparty Name [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_CounterpartyNameAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:type="locator"/>
    <link:label xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Counterparty Name [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="us-gaap_AccountingStandardsUpdate201409Member" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountingStandardsUpdate201409Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounting Standards Update 2014-09 [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingStandardsUpdate201409Member" xlink:to="us-gaap_AccountingStandardsUpdate201409Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member" xlink:label="us-gaap_AccountingStandardsUpdate201602Member" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountingStandardsUpdate201602Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounting Standards Update 2016-02 [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingStandardsUpdate201602Member" xlink:to="us-gaap_AccountingStandardsUpdate201602Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued" xlink:label="us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued</link:label>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued" xlink:to="us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InvestmentPolicyTextBlock" xlink:label="us-gaap_InvestmentPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InvestmentPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentPolicyTextBlock" xlink:to="us-gaap_InvestmentPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TypeOfAdoptionMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Type of Adoption [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="us-gaap_TypeOfAdoptionMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains" xlink:label="us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Foreign currency derivative</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains" xlink:to="us-gaap_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" xlink:label="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment</link:label>
    <link:label xlink:label="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Fixed assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" xlink:to="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustments for New Accounting Pronouncements [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MidCapFinancialServicesLLCMember" xlink:label="bcrx_MidCapFinancialServicesLLCMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MidCapFinancialServicesLLCMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">MidCap Financial Services, LLC [Member]</link:label>
    <link:label xlink:label="bcrx_MidCapFinancialServicesLLCMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents MidCap Financial Services, LLC entity.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MidCapFinancialServicesLLCMember" xlink:to="bcrx_MidCapFinancialServicesLLCMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestAndOtherIncome" xlink:label="us-gaap_InterestAndOtherIncome" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InterestAndOtherIncome-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest and other income</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestAndOtherIncome" xlink:to="us-gaap_InterestAndOtherIncome-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_SeniorCreditFacilityMember" xlink:label="bcrx_SeniorCreditFacilityMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_SeniorCreditFacilityMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Senior Credit Facility [Member]</link:label>
    <link:label xlink:label="bcrx_SeniorCreditFacilityMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents senior credit facility. Credit facilities provide capital to borrowers without the need to structure a loan for each borrowing.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_SeniorCreditFacilityMember" xlink:to="bcrx_SeniorCreditFacilityMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CostsAndExpenses" xlink:label="us-gaap_CostsAndExpenses" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CostsAndExpenses-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CostsAndExpenses</link:label>
    <link:label xlink:label="us-gaap_CostsAndExpenses-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total operating expenses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostsAndExpenses" xlink:to="us-gaap_CostsAndExpenses-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CostsAndExpensesAbstract" xlink:label="us-gaap_CostsAndExpensesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CostsAndExpensesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expenses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostsAndExpensesAbstract" xlink:to="us-gaap_CostsAndExpensesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AccruedDevelopmentCosts" xlink:label="bcrx_AccruedDevelopmentCosts" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AccruedDevelopmentCosts-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AccruedDevelopmentCosts</link:label>
    <link:label xlink:label="bcrx_AccruedDevelopmentCosts-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Development costs</link:label>
    <link:label xlink:label="bcrx_AccruedDevelopmentCosts-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents accrued development costs.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AccruedDevelopmentCosts" xlink:to="bcrx_AccruedDevelopmentCosts-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability" xlink:label="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability</link:label>
    <link:label xlink:label="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability" xlink:to="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_AccruedInventoryExpense" xlink:label="bcrx_AccruedInventoryExpense" xlink:type="locator"/>
    <link:label xlink:label="bcrx_AccruedInventoryExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_AccruedInventoryExpense</link:label>
    <link:label xlink:label="bcrx_AccruedInventoryExpense-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Inventory</link:label>
    <link:label xlink:label="bcrx_AccruedInventoryExpense-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the amount of accrued inventory expense.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_AccruedInventoryExpense" xlink:to="bcrx_AccruedInventoryExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RetainedEarningsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Retained Earnings [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsMember" xlink:to="us-gaap_RetainedEarningsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="us-gaap_ProceedsFromStockOptionsExercised" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net proceeds from common stock issued under stock-based compensation plans</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromStockOptionsExercised" xlink:to="us-gaap_ProceedsFromStockOptionsExercised-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_MundipharmaMember" xlink:label="bcrx_MundipharmaMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_MundipharmaMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Mundipharma [Member]</link:label>
    <link:label xlink:label="bcrx_MundipharmaMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to Mundipharma.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_MundipharmaMember" xlink:to="bcrx_MundipharmaMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale of common stock, net</link:label>
    <link:label xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from Issuance of Common Stock</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Initial Application Period Cumulative Effect Transition [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:to="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Initial Application Period Cumulative Effect Transition [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:to="us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Difference between Revenue Guidance in Effect before and after Topic 606 [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:to="us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdditionalPaidInCapitalMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional Paid-in Capital [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PercentageOfCarryingAmountInExcessOfFairValue1" xlink:label="bcrx_PercentageOfCarryingAmountInExcessOfFairValue1" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PercentageOfCarryingAmountInExcessOfFairValue1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PercentageOfCarryingAmountInExcessOfFairValue1</link:label>
    <link:label xlink:label="bcrx_PercentageOfCarryingAmountInExcessOfFairValue1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of Carrying Amount in Excess of Fair Value</link:label>
    <link:label xlink:label="bcrx_PercentageOfCarryingAmountInExcessOfFairValue1-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the percentage of carrying amount in excess of fair value.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PercentageOfCarryingAmountInExcessOfFairValue1" xlink:to="bcrx_PercentageOfCarryingAmountInExcessOfFairValue1-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_LeasedEquipmentMember" xlink:label="bcrx_LeasedEquipmentMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_LeasedEquipmentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Leased Equipment [Member]</link:label>
    <link:label xlink:label="bcrx_LeasedEquipmentMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to leased equipment.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_LeasedEquipmentMember" xlink:to="bcrx_LeasedEquipmentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_LaboratoryEquipmentMember" xlink:label="bcrx_LaboratoryEquipmentMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_LaboratoryEquipmentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Laboratory Equipment [Member]</link:label>
    <link:label xlink:label="bcrx_LaboratoryEquipmentMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to laboratory equipment.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_LaboratoryEquipmentMember" xlink:to="bcrx_LaboratoryEquipmentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementEquityComponentsAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Components [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_StatementEquityComponentsAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EquityComponentDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Component [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_EquityComponentDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LongTermDebt-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LongTermDebt</link:label>
    <link:label xlink:label="us-gaap_LongTermDebt-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebt" xlink:to="us-gaap_LongTermDebt-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRevenueCurrent" xlink:label="us-gaap_DeferredRevenueCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredRevenueCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred collaboration revenue</link:label>
    <link:label xlink:label="us-gaap_DeferredRevenueCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred revenue</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRevenueCurrent" xlink:to="us-gaap_DeferredRevenueCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" xlink:label="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Vest Upon Successful Completion of Specific Development Milestones [Member]</link:label>
    <link:label xlink:label="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents vesting upon successful completion of specific development milestones.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" xlink:to="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_December2014Member" xlink:label="bcrx_December2014Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_December2014Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">December 2014 [Member]</link:label>
    <link:label xlink:label="bcrx_December2014Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents award date of December 2014.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_December2014Member" xlink:to="bcrx_December2014Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCredit" xlink:label="us-gaap_LineOfCredit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCredit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Senior credit facility</link:label>
    <link:label xlink:label="us-gaap_LineOfCredit-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term Line of Credit, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCredit" xlink:to="us-gaap_LineOfCredit-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_August2013Member" xlink:label="bcrx_August2013Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_August2013Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">August 2013 [Member]</link:label>
    <link:label xlink:label="bcrx_August2013Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents award date of August 2013.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_August2013Member" xlink:to="bcrx_August2013Member-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_Vest25PercentEachYearUntilFullyVestedMember" xlink:label="bcrx_Vest25PercentEachYearUntilFullyVestedMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_Vest25PercentEachYearUntilFullyVestedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Vest 25% Each Year Until Fully Vested [Member]</link:label>
    <link:label xlink:label="bcrx_Vest25PercentEachYearUntilFullyVestedMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents vest 25% each year until fully vested.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_Vest25PercentEachYearUntilFullyVestedMember" xlink:to="bcrx_Vest25PercentEachYearUntilFullyVestedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember" xlink:label="us-gaap_StateAndLocalJurisdictionMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StateAndLocalJurisdictionMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">State and Local Jurisdiction [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StateAndLocalJurisdictionMember" xlink:to="us-gaap_StateAndLocalJurisdictionMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxAuthorityAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax Authority [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxAuthorityDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax Authority [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxAuthorityDomain" xlink:to="us-gaap_IncomeTaxAuthorityDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Disaggregation of Revenue [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:to="us-gaap_DisaggregationOfRevenueTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="us-gaap_DomesticCountryMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DomesticCountryMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Domestic Tax Authority [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DomesticCountryMember" xlink:to="us-gaap_DomesticCountryMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt" xlink:label="us-gaap_RepaymentsOfLongTermDebt" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RepaymentsOfLongTermDebt-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_RepaymentsOfLongTermDebt</link:label>
    <link:label xlink:label="us-gaap_RepaymentsOfLongTermDebt-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Repayments of Long-term Debt, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfLongTermDebt" xlink:to="us-gaap_RepaymentsOfLongTermDebt-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OfficeEquipmentMember" xlink:label="us-gaap_OfficeEquipmentMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OfficeEquipmentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Office Equipment [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OfficeEquipmentMember" xlink:to="us-gaap_OfficeEquipmentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="us-gaap_ComputerEquipmentMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ComputerEquipmentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Computer Equipment [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComputerEquipmentMember" xlink:to="us-gaap_ComputerEquipmentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:to="us-gaap_CashAndCashEquivalentsPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_BalanceSheetLocationAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Balance Sheet Location [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="us-gaap_BalanceSheetLocationDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_BalanceSheetLocationDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Balance Sheet Location [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="us-gaap_BalanceSheetLocationDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy" xlink:label="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy" xlink:to="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReceivablesPolicyTextBlock" xlink:label="us-gaap_ReceivablesPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ReceivablesPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Receivables, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReceivablesPolicyTextBlock" xlink:to="us-gaap_ReceivablesPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SoftwareDevelopmentMember" xlink:label="us-gaap_SoftwareDevelopmentMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SoftwareDevelopmentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Software Development [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SoftwareDevelopmentMember" xlink:to="us-gaap_SoftwareDevelopmentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="us-gaap_UnrecognizedTaxBenefits" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefits-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_UnrecognizedTaxBenefits</link:label>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefits-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Balance</link:label>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefits-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Balance</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefits" xlink:to="us-gaap_UnrecognizedTaxBenefits-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">General and Administrative Expense [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpenseMember" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountingPoliciesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounting Policies [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_AccountingPoliciesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SignificantAccountingPoliciesTextBlock" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Significant Accounting Policies [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:to="us-gaap_SignificantAccountingPoliciesTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Basis of Accounting, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:to="us-gaap_BasisOfAccountingPolicyPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:label="us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption</link:label>
    <link:label xlink:label="us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Impact to retained earnings from adoption of ASC 606</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:to="us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions" xlink:label="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additions to prior period tax positions</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions" xlink:to="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions" xlink:label="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions</link:label>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Reductions to prior period tax provisions</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions" xlink:to="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions" xlink:label="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additions to current period tax positions</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions" xlink:to="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis" xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Billing Status, Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis" xlink:to="us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research and Development Expense [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReceivablesBillingStatusDomain" xlink:label="us-gaap_ReceivablesBillingStatusDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ReceivablesBillingStatusDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Receivables Billing Status [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReceivablesBillingStatusDomain" xlink:to="us-gaap_ReceivablesBillingStatusDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnbilledRevenuesMember" xlink:label="us-gaap_UnbilledRevenuesMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnbilledRevenuesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unbilled Revenues [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnbilledRevenuesMember" xlink:to="us-gaap_UnbilledRevenuesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BilledRevenuesMember" xlink:label="us-gaap_BilledRevenuesMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_BilledRevenuesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Billed Revenues [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BilledRevenuesMember" xlink:to="us-gaap_BilledRevenuesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOfSecuredDebt" xlink:label="us-gaap_ProceedsFromIssuanceOfSecuredDebt" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromIssuanceOfSecuredDebt-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ProceedsFromIssuanceOfSecuredDebt</link:label>
    <link:label xlink:label="us-gaap_ProceedsFromIssuanceOfSecuredDebt-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from Issuance of Secured Debt</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfSecuredDebt" xlink:to="us-gaap_ProceedsFromIssuanceOfSecuredDebt-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeStatementLocationAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Statement Location [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeStatementLocationDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Statement Location [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_IncomeStatementLocationDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TypeOfArrangementAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Type of Arrangement and Non-arrangement Transactions [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_TypeOfArrangementAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal Entity of Counterparty, Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:to="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:label="us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LegalEntityTypeOfCounterpartyDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal Entity Type of Counterparty [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:to="us-gaap_LegalEntityTypeOfCounterpartyDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollateralAlreadyPostedAggregateFairValue" xlink:label="us-gaap_CollateralAlreadyPostedAggregateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CollateralAlreadyPostedAggregateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CollateralAlreadyPostedAggregateFairValue</link:label>
    <link:label xlink:label="us-gaap_CollateralAlreadyPostedAggregateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Collateral Already Posted, Aggregate Fair Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CollateralAlreadyPostedAggregateFairValue" xlink:to="us-gaap_CollateralAlreadyPostedAggregateFairValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollaborativeArrangementDisclosureTextBlock" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Collaborative Arrangement Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CollaborativeArrangementDisclosureTextBlock" xlink:to="us-gaap_CollaborativeArrangementDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardAmount" xlink:label="us-gaap_TaxCreditCarryforwardAmount" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TaxCreditCarryforwardAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_TaxCreditCarryforwardAmount</link:label>
    <link:label xlink:label="us-gaap_TaxCreditCarryforwardAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Tax Credit Carryforward, Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardAmount" xlink:to="us-gaap_TaxCreditCarryforwardAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchMember" xlink:label="us-gaap_ResearchMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research Tax Credit Carryforward [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchMember" xlink:to="us-gaap_ResearchMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount</link:label>
    <link:label xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted average shares outstanding (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfLinesOfCredit" xlink:label="us-gaap_RepaymentsOfLinesOfCredit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RepaymentsOfLinesOfCredit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_RepaymentsOfLinesOfCredit</link:label>
    <link:label xlink:label="us-gaap_RepaymentsOfLinesOfCredit-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Payment of senior credit facility</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfLinesOfCredit" xlink:to="us-gaap_RepaymentsOfLinesOfCredit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardAxis" xlink:label="us-gaap_TaxCreditCarryforwardAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TaxCreditCarryforwardAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Tax Credit Carryforward [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardAxis" xlink:to="us-gaap_TaxCreditCarryforwardAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain" xlink:label="us-gaap_TaxCreditCarryforwardNameDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TaxCreditCarryforwardNameDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Tax Credit Carryforward, Name [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardNameDomain" xlink:to="us-gaap_TaxCreditCarryforwardNameDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EarningsPerShareBasicAndDiluted-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Basic and diluted net loss per common share (in dollars per share)</link:label>
    <link:label xlink:label="us-gaap_EarningsPerShareBasicAndDiluted-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Basic and diluted net loss per share (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAndDiluted" xlink:to="us-gaap_EarningsPerShareBasicAndDiluted-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLossCarryforwards" xlink:label="us-gaap_OperatingLossCarryforwards" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLossCarryforwards-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLossCarryforwards</link:label>
    <link:label xlink:label="us-gaap_OperatingLossCarryforwards-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating Loss Carryforwards, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLossCarryforwards" xlink:to="us-gaap_OperatingLossCarryforwards-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="us-gaap_ProceedsFromLinesOfCredit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ProceedsFromLinesOfCredit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from senior credit facility</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLinesOfCredit" xlink:to="us-gaap_ProceedsFromLinesOfCredit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementTable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Table]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementTable-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExercisePriceRange01Member" xlink:label="bcrx_ExercisePriceRange01Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExercisePriceRange01Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range 01 [Member]</link:label>
    <link:label xlink:label="bcrx_ExercisePriceRange01Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the first exercise range.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExercisePriceRange01Member" xlink:to="bcrx_ExercisePriceRange01Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="us-gaap_StatementScenarioAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementScenarioAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Scenario [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementScenarioAxis" xlink:to="us-gaap_StatementScenarioAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementOfFinancialPositionAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Financial Position [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementOfFinancialPositionAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="us-gaap_ScenarioUnspecifiedDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScenarioUnspecifiedDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Scenario, Unspecified [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScenarioUnspecifiedDomain" xlink:to="us-gaap_ScenarioUnspecifiedDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Thereafter</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExercisePriceRange03Member" xlink:label="bcrx_ExercisePriceRange03Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExercisePriceRange03Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range 03 [Member]</link:label>
    <link:label xlink:label="bcrx_ExercisePriceRange03Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the third exercise range.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExercisePriceRange03Member" xlink:to="bcrx_ExercisePriceRange03Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDue</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating Leases, Future Minimum Payments Due, Total</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total minimum payments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDue-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExercisePriceRange02Member" xlink:label="bcrx_ExercisePriceRange02Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExercisePriceRange02Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range 02 [Member]</link:label>
    <link:label xlink:label="bcrx_ExercisePriceRange02Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the second exercise range.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExercisePriceRange02Member" xlink:to="bcrx_ExercisePriceRange02Member-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExercisePriceRange05Member" xlink:label="bcrx_ExercisePriceRange05Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExercisePriceRange05Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range 05 [Member]</link:label>
    <link:label xlink:label="bcrx_ExercisePriceRange05Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the fifth exercise range.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExercisePriceRange05Member" xlink:to="bcrx_ExercisePriceRange05Member-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExercisePriceRange04Member" xlink:label="bcrx_ExercisePriceRange04Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExercisePriceRange04Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range 04 [Member]</link:label>
    <link:label xlink:label="bcrx_ExercisePriceRange04Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the fourth exercise range.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExercisePriceRange04Member" xlink:to="bcrx_ExercisePriceRange04Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2022</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ExercisePriceRange06Member" xlink:label="bcrx_ExercisePriceRange06Member" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ExercisePriceRange06Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range 06 [Member]</link:label>
    <link:label xlink:label="bcrx_ExercisePriceRange06Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the sixth exercise range.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ExercisePriceRange06Member" xlink:to="bcrx_ExercisePriceRange06Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2023</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards" xlink:label="bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards" xlink:type="locator"/>
    <link:label xlink:label="bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expiration of attribute carryforwards</link:label>
    <link:label xlink:label="bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Income tax reconciliation income tax expense benefit expiration of carryforwards.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards" xlink:to="bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2020</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementOfCashFlowsAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Cash Flows [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2021</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_UpfrontPaymentsReceivableAmount" xlink:label="bcrx_UpfrontPaymentsReceivableAmount" xlink:type="locator"/>
    <link:label xlink:label="bcrx_UpfrontPaymentsReceivableAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_UpfrontPaymentsReceivableAmount</link:label>
    <link:label xlink:label="bcrx_UpfrontPaymentsReceivableAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Upfront Payments Receivable Amount</link:label>
    <link:label xlink:label="bcrx_UpfrontPaymentsReceivableAmount-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents upfront payments receivable.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_UpfrontPaymentsReceivableAmount" xlink:to="bcrx_UpfrontPaymentsReceivableAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_PotentialMilestonePaymentsReceivable" xlink:label="bcrx_PotentialMilestonePaymentsReceivable" xlink:type="locator"/>
    <link:label xlink:label="bcrx_PotentialMilestonePaymentsReceivable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_PotentialMilestonePaymentsReceivable</link:label>
    <link:label xlink:label="bcrx_PotentialMilestonePaymentsReceivable-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Potential Milestone Payments Receivable</link:label>
    <link:label xlink:label="bcrx_PotentialMilestonePaymentsReceivable-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents potential milestone payments receivable based on possibility of future event payments.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_PotentialMilestonePaymentsReceivable" xlink:to="bcrx_PotentialMilestonePaymentsReceivable-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementOfStockholdersEquityAbstract" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementOfStockholdersEquityAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Stockholders' Equity [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="us-gaap_StatementOfStockholdersEquityAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent</link:label>
    <link:label xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2019</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeStatementAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Statement [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_IncomeStatementAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">2021</link:label>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">2022</link:label>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_CollaborativeAndOtherResearchAndDevelopmentMember" xlink:label="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Collaborative and Other Research and Development [Member]</link:label>
    <link:label xlink:label="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to Collaborative and other research and development.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember" xlink:to="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Accrued Liabilities [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock" xlink:to="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">2019</link:label>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">2020</link:label>
    <link:label xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock" xlink:label="us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Quarterly Financial Information [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock" xlink:to="us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" xlink:to="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock" xlink:label="us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock" xlink:to="us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember" xlink:label="bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Laboratory Equipment, Office Equipment and Software [Member]</link:label>
    <link:label xlink:label="bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to laboratory equipment, office equipment and software.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember" xlink:to="bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Deferred Tax Assets and Liabilities [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:to="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" xlink:to="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GovernmentContractReceivable" xlink:label="us-gaap_GovernmentContractReceivable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_GovernmentContractReceivable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_GovernmentContractReceivable</link:label>
    <link:label xlink:label="us-gaap_GovernmentContractReceivable-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Government Contract Receivable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GovernmentContractReceivable" xlink:to="us-gaap_GovernmentContractReceivable-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_BirminghamResearchFacilityMember" xlink:label="bcrx_BirminghamResearchFacilityMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_BirminghamResearchFacilityMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Birmingham Research Facility [Member]</link:label>
    <link:label xlink:label="bcrx_BirminghamResearchFacilityMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the Birmingham Research Facility.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_BirminghamResearchFacilityMember" xlink:to="bcrx_BirminghamResearchFacilityMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:label="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">New Accounting Pronouncements and Changes in Accounting Principles [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:to="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:label="us-gaap_ScheduleOfNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:to="us-gaap_ScheduleOfNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherCommitmentsAxis" xlink:label="us-gaap_OtherCommitmentsAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherCommitmentsAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Commitments [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherCommitmentsAxis" xlink:to="us-gaap_OtherCommitmentsAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherCommitmentsDomain" xlink:label="us-gaap_OtherCommitmentsDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherCommitmentsDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Commitments [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherCommitmentsDomain" xlink:to="us-gaap_OtherCommitmentsDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationOtherAdjustments" xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncomeTaxReconciliationOtherAdjustments</link:label>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationOtherAdjustments" xlink:to="us-gaap_IncomeTaxReconciliationOtherAdjustments-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income tax benefit at federal statutory rate, percentage</link:label>
    <link:label xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:to="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate" xlink:label="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Rate change</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate" xlink:to="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Change in valuation allowance</link:label>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:to="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased" xlink:label="us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased</link:label>
    <link:label xlink:label="us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Stock Ownership Plan (ESOP), Weighted Average Purchase Price of Shares Purchased</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased" xlink:to="us-gaap_EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PaymentsForProceedsFromHedgeInvestingActivities</link:label>
    <link:label xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Payments for (Proceeds from) Hedge, Investing Activities, Total</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:to="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research and Development Arrangement, Contract to Perform for Others, Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo" xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo" xlink:type="locator"/>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Year Two</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Employee service share based compensation nonvested awards compensation cost expected to be recognized year two.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo" xlink:to="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Research and Development Arrangement, Contract to Perform for Others, Type [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree" xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree" xlink:type="locator"/>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Year Three</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Employee service share based compensation nonvested awards compensation cost expected to be recognized year three.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree" xlink:to="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour" xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour" xlink:type="locator"/>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Year Four</link:label>
    <link:label xlink:label="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Employee service share based compensation nonvested awards compensation cost expected to be recognized year four.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour" xlink:to="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_NumberOfMajorCustomers" xlink:label="bcrx_NumberOfMajorCustomers" xlink:type="locator"/>
    <link:label xlink:label="bcrx_NumberOfMajorCustomers-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_NumberOfMajorCustomers</link:label>
    <link:label xlink:label="bcrx_NumberOfMajorCustomers-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of Major Customers</link:label>
    <link:label xlink:label="bcrx_NumberOfMajorCustomers-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the number of major customers accounting for 10% or more of the specified concentration risk benchmark, which includes, but not limited to, sales revenue, accounts receivable, etc.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_NumberOfMajorCustomers" xlink:to="bcrx_NumberOfMajorCustomers-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate" xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate</link:label>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, First Vesting Period After Grant Date</link:label>
    <link:label xlink:label="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Share based compensation arrangement by share based payment award first vesting period after grant date.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate" xlink:to="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFirstVestingPeriodAfterGrantDate-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRentCreditNoncurrent" xlink:label="us-gaap_DeferredRentCreditNoncurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DeferredRentCreditNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred rent</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRentCreditNoncurrent" xlink:to="us-gaap_DeferredRentCreditNoncurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_LeaseFinancingObligationNetOfCurrent" xlink:label="bcrx_LeaseFinancingObligationNetOfCurrent" xlink:type="locator"/>
    <link:label xlink:label="bcrx_LeaseFinancingObligationNetOfCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lease financing obligation</link:label>
    <link:label xlink:label="bcrx_LeaseFinancingObligationNetOfCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lease Financing Obligation, Net of Current</link:label>
    <link:label xlink:label="bcrx_LeaseFinancingObligationNetOfCurrent-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Lease Financing obligation as of the balance sheet date.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_LeaseFinancingObligationNetOfCurrent" xlink:to="bcrx_LeaseFinancingObligationNetOfCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_ThreeCustomersMember" xlink:label="bcrx_ThreeCustomersMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_ThreeCustomersMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Three Customers [Member]</link:label>
    <link:label xlink:label="bcrx_ThreeCustomersMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Information pertaining to the three specialty distributors as customers.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_ThreeCustomersMember" xlink:to="bcrx_ThreeCustomersMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockholdersEquity</link:label>
    <link:label xlink:label="us-gaap_StockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total stockholders&#8217; equity</link:label>
    <link:label xlink:label="us-gaap_StockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Balance</link:label>
    <link:label xlink:label="us-gaap_StockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Balance</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpense" xlink:label="us-gaap_IncomeTaxReconciliationNondeductibleExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationNondeductibleExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Permanent items</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationNondeductibleExpense" xlink:to="us-gaap_IncomeTaxReconciliationNondeductibleExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="bcrx-20181231.xsd#bcrx_LongTermLiabilitiesMember" xlink:label="bcrx_LongTermLiabilitiesMember" xlink:type="locator"/>
    <link:label xlink:label="bcrx_LongTermLiabilitiesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long Term Liabilities [Member]</link:label>
    <link:label xlink:label="bcrx_LongTermLiabilitiesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents long term liabilities.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="bcrx_LongTermLiabilitiesMember" xlink:to="bcrx_LongTermLiabilitiesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementClassOfStockAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Stock [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_StatementClassOfStockAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding Weighted Average Exercise Price (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1" xlink:to="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax</link:label>
    <link:label xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Gross Unrealized Losses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding Weighted Average Remaining Life (Year)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gross Unrealized Gains</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercisable Number (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercisable Weighted Average Exercise Price (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1" xlink:to="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Upper Exercise Price Range (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding Number (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amortized Cost</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeForwardExchangeRate1" xlink:label="us-gaap_DerivativeForwardExchangeRate1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DerivativeForwardExchangeRate1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DerivativeForwardExchangeRate1</link:label>
    <link:label xlink:label="us-gaap_DerivativeForwardExchangeRate1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative, Forward Exchange Rate</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeForwardExchangeRate1" xlink:to="us-gaap_DerivativeForwardExchangeRate1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">State and local income taxes net of federal tax benefit</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:to="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercise Price Range [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxReconciliationTaxCreditsResearch" xlink:label="us-gaap_IncomeTaxReconciliationTaxCreditsResearch" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationTaxCreditsResearch-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncomeTaxReconciliationTaxCreditsResearch</link:label>
    <link:label xlink:label="us-gaap_IncomeTaxReconciliationTaxCreditsResearch-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Research and development tax credits</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationTaxCreditsResearch" xlink:to="us-gaap_IncomeTaxReconciliationTaxCreditsResearch-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lower Exercise Price Range (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit-label" xlink:type="arc"/>
  </link:labelLink>
</link:linkbase>
