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  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPurchasePriceAmount" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPurchasePriceAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_InterestPaidRoyaltyFinancingLiabilities" abstract="false" name="InterestPaidRoyaltyFinancingLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_TwentyTwentyRPIRoyaltyAgreementMember" abstract="true" name="TwentyTwentyRPIRoyaltyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_TwentyTwentyOneRPIRoyaltyAgreementMember" abstract="true" name="TwentyTwentyOneRPIRoyaltyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_OMERSRoyaltyAgreementMember" abstract="true" name="OMERSRoyaltyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_RoyaltyMontizationsRollForward" abstract="true" name="RoyaltyMontizationsRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_RoyaltyFinancingLiabilities" abstract="false" name="RoyaltyFinancingLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_RoyaltyRevenuesPayable" abstract="false" name="RoyaltyRevenuesPayable" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_TermLoanTrancheAMember" abstract="true" name="TermLoanTrancheAMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_LoanAgreementMember" abstract="true" name="LoanAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_TermLoanTrancheBMember" abstract="true" name="TermLoanTrancheBMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_TermLoanTrancheCMember" abstract="true" name="TermLoanTrancheCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_TermLoanTrancheDMember" abstract="true" name="TermLoanTrancheDMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_PharmakonAdvisorsLPMember" abstract="true" name="PharmakonAdvisorsLPMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AthyriumMember" abstract="true" name="AthyriumMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_SeniorCreditFacilityMember" abstract="true" name="SeniorCreditFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_DebtCovenantTermsAxis" abstract="true" name="DebtCovenantTermsAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_DebtCovenantTermsDomain" abstract="true" name="DebtCovenantTermsDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_PikInterestPaymentIsMadeMember" abstract="true" name="PikInterestPaymentIsMadeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_BetweenTheSecondAndThirdAnniversariesMember" abstract="true" name="BetweenTheSecondAndThirdAnniversariesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AfterFourthAnniversaryMember" abstract="true" name="AfterFourthAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AfterThirdAnniversaryMember" abstract="true" name="AfterThirdAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_DebtInstrumentCapitalizedInterestRate" abstract="false" name="DebtInstrumentCapitalizedInterestRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="bcrx_DebtInstrumentVariableRateFloor" abstract="false" name="DebtInstrumentVariableRateFloor" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="bcrx_DebtInstrumentPrepaymentFeePercentageOfPrincipalVoluntaryPayments" abstract="false" name="DebtInstrumentPrepaymentFeePercentageOfPrincipalVoluntaryPayments" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_DebtInstrumentPrepaymentPremium" abstract="false" name="DebtInstrumentPrepaymentPremium" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_UnamortizedDeferredFinancingCosts" abstract="false" name="UnamortizedDeferredFinancingCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PercentOfInterestPayment" abstract="false" name="PercentOfInterestPayment" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="bcrx_OperatingLeaseRightOfUseAssetAccumulatedAmortization" abstract="false" name="OperatingLeaseRightOfUseAssetAccumulatedAmortization" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_FinancingLeaseExpense" abstract="false" name="FinancingLeaseExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_OperatingLeaseAssets" abstract="true" name="OperatingLeaseAssets" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_FinanceLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="FinanceLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_NonCashIncreaseInOperatingLeaseAssetsDueToRemeasurementOfOperatingLeaseLiabilities" abstract="false" name="NonCashIncreaseInOperatingLeaseAssetsDueToRemeasurementOfOperatingLeaseLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_IncentivePlanMember" abstract="true" name="IncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_InducementPlanMember" abstract="true" name="InducementPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_EmployeeStockPurchasePlanMember" abstract="true" name="EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_ShareBasedPaymentArrangementNumberOfPlans" abstract="false" name="ShareBasedPaymentArrangementNumberOfPlans" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_ToriiPharmaceuticalCoMember" abstract="true" name="ToriiPharmaceuticalCoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_ClearsideBiomedicalIncMember" abstract="true" name="ClearsideBiomedicalIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_HHSOfficeOfTheAdministrationForStrategicPreparednessAndResponseMember" abstract="true" name="HHSOfficeOfTheAdministrationForStrategicPreparednessAndResponseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesOf2MillionMember" abstract="true" name="AnnualNetSalesOf2MillionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesGreaterThan15MillionMember" abstract="true" name="AnnualNetSalesGreaterThan15MillionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_RAPIVABMember" abstract="true" name="RAPIVABMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeMilestone" abstract="false" name="PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeMilestone" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_RoyaltyRateIfMaintainsSakigakeDesignation" abstract="false" name="RoyaltyRateIfMaintainsSakigakeDesignation" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_MaximumCustomaryReductionOnRoyaltyRate" abstract="false" name="MaximumCustomaryReductionOnRoyaltyRate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_RoyaltyRate" abstract="false" name="RoyaltyRate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_CollaborativeAgreementContractValue" abstract="false" name="CollaborativeAgreementContractValue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_MaximumNumberOfProductsPermittedToBeObtainedDoses" abstract="false" name="MaximumNumberOfProductsPermittedToBeObtainedDoses" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_ContractTerm" abstract="false" name="ContractTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_NumberOfOptionalOrderingPeriods" abstract="false" name="NumberOfOptionalOrderingPeriods" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_NumberOfProductDeliveredDoses" abstract="false" name="NumberOfProductDeliveredDoses" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_LicenseAgreementUpfrontPayment" abstract="false" name="LicenseAgreementUpfrontPayment" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PotentialMilestonePaymentsPayable" abstract="false" name="PotentialMilestonePaymentsPayable" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PotentialMilestonePaymentsPayableIfRegulatoryApprovalBeforeMilestone" abstract="false" name="PotentialMilestonePaymentsPayableIfRegulatoryApprovalBeforeMilestone" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_LicenseAgreementNumberOfMilestonePayments" abstract="false" name="LicenseAgreementNumberOfMilestonePayments" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_LicenseAgreementAnnualGlobalNetSales" abstract="false" name="LicenseAgreementAnnualGlobalNetSales" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_LicenseAgreementRoyaltyPaymentNumberOfTiers" abstract="false" name="LicenseAgreementRoyaltyPaymentNumberOfTiers" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_CashCashEquivalentsShortAndLongTermInvestments" abstract="false" name="CashCashEquivalentsShortAndLongTermInvestments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_ReportableSegmentMember" abstract="true" name="ReportableSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_BerotralstatMember" abstract="true" name="BerotralstatMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_FactorDProgramMember" abstract="true" name="FactorDProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_BCX17725Member" abstract="true" name="BCX17725Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AvoralstatMember" abstract="true" name="AvoralstatMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_OtherResearchPreclinicalAndDevelopmentCostsMember" abstract="true" name="OtherResearchPreclinicalAndDevelopmentCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_SegmentReportingAdjustmentsAndReconcilingItemsAmount" abstract="false" name="SegmentReportingAdjustmentsAndReconcilingItemsAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_IncrementalCommonSharesAttributableToDilutiveEffectOfSharePurchasePlans" abstract="false" name="IncrementalCommonSharesAttributableToDilutiveEffectOfSharePurchasePlans" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
</xs:schema>
