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  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesMaximumTieredProfitSharePercentageOnPermittedSalesInOtherMarkets" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesMaximumTieredProfitSharePercentageOnPermittedSalesInOtherMarkets" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_DebtInstrumentExitFeePercentageOfPrincipal" abstract="false" name="DebtInstrumentExitFeePercentageOfPrincipal" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock" abstract="false" name="ScheduleOfReceivablesFromCollaborationsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="bcrx_AnnualNetSalesOver230000Member" abstract="true" name="AnnualNetSalesOver230000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_MaximumCustomaryReductionOnRoyaltyRate" abstract="false" name="MaximumCustomaryReductionOnRoyaltyRate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_AnnualNetSalesUnder350000Member" abstract="true" name="AnnualNetSalesUnder350000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_RoyaltyExpenseReversalOfExpense" abstract="false" name="RoyaltyExpenseReversalOfExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_AnnualNetSalesUnder150000Member" abstract="true" name="AnnualNetSalesUnder150000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesBetween150000And230000Member" abstract="true" name="AnnualNetSalesBetween150000And230000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_TermALoanMember" abstract="true" name="TermALoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_PercentOfInterestPayment" abstract="false" name="PercentOfInterestPayment" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <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_ProceedsFromIssuanceOfCommonStockIssuedForServices" abstract="false" name="ProceedsFromIssuanceOfCommonStockIssuedForServices" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_AthyriumMember" abstract="true" name="AthyriumMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_SignificantAccountingPoliciesAndConcentrationsOfRiskTable" abstract="true" name="SignificantAccountingPoliciesAndConcentrationsOfRiskTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <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_TwentyTwentyRPIRoyaltyAgreementMember" abstract="true" name="TwentyTwentyRPIRoyaltyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesBetween350000And550000Member" abstract="true" name="AnnualNetSalesBetween350000And550000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_OMERSRoyaltyAgreementMember" abstract="true" name="OMERSRoyaltyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_DebtInstrumentPrepaymentFeePercentageOfPrincipalVoluntaryPayments" abstract="false" name="DebtInstrumentPrepaymentFeePercentageOfPrincipalVoluntaryPayments" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_MidCapFinancialServicesLLCMember" abstract="true" name="MidCapFinancialServicesLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_IncentivePlanMember" abstract="true" name="IncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_LicenseAgreementRoyaltyPaymentNumberOfTiers" abstract="false" name="LicenseAgreementRoyaltyPaymentNumberOfTiers" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <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_RoyaltyFinancingLiabilitiesTextBlock" abstract="false" name="RoyaltyFinancingLiabilitiesTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="bcrx_RoyaltyFinancingLiabilitiesNoncurrent" abstract="false" name="RoyaltyFinancingLiabilitiesNoncurrent" nillable="true" xbrli:periodType="instant" 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_RPI2021And2020IntermediateFinanceTrustMember" abstract="true" name="RPI2021And2020IntermediateFinanceTrustMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_NancyJ.HutsonMember" abstract="true" name="NancyJ.HutsonMember" 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-types1:domainItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_SignificantAccountingPoliciesAndConcentrationsOfRiskLineItems" abstract="true" name="SignificantAccountingPoliciesAndConcentrationsOfRiskLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_The2021RPIRoyaltyPurchaseAgreementMember" abstract="true" name="The2021RPIRoyaltyPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_TradeReceivablesTextBlock" abstract="false" name="TradeReceivablesTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <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_AccruedExpensesPolicyTextBlock" abstract="false" name="AccruedExpensesPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <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_LongTermInvestmentMaturityMinimum" abstract="false" name="LongTermInvestmentMaturityMinimum" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_OtherIncomeFromContractWithCustomerMember" abstract="true" name="OtherIncomeFromContractWithCustomerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_LesseeOperatingLeaseAssetsAndLiabilitiesTableTextBlock" abstract="false" name="LesseeOperatingLeaseAssetsAndLiabilitiesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="bcrx_EmployeeStockPurchasePlanMember" abstract="true" name="EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_TermBAndCLoanMember" abstract="true" name="TermBAndCLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1: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:schema>
