000087504512/312025Q2false146,614,598threefive yearsonesix monthxbrli:sharesiso4217:USDiso4217:USDxbrli:sharesbiib:segmentxbrli:purebiib:Employeeutr:sqftbiib:wholesalerbiib:productiso4217:EUR00008750452025-01-012025-06-3000008750452025-07-290000875045us-gaap:ProductMember2025-04-012025-06-300000875045us-gaap:ProductMember2024-04-012024-06-300000875045us-gaap:ProductMember2025-01-012025-06-300000875045us-gaap:ProductMember2024-01-012024-06-300000875045biib:Revenuesfromanticd20therapeuticprogramsMember2025-04-012025-06-300000875045biib:Revenuesfromanticd20therapeuticprogramsMember2024-04-012024-06-300000875045biib:Revenuesfromanticd20therapeuticprogramsMember2025-01-012025-06-300000875045biib:Revenuesfromanticd20therapeuticprogramsMember2024-01-012024-06-300000875045biib:LEQEMBICollaborationMember2025-04-012025-06-300000875045biib:LEQEMBICollaborationMember2024-04-012024-06-300000875045biib:LEQEMBICollaborationMember2025-01-012025-06-300000875045biib:LEQEMBICollaborationMember2024-01-012024-06-300000875045us-gaap:ProductAndServiceOtherMember2025-04-012025-06-300000875045us-gaap:ProductAndServiceOtherMember2024-04-012024-06-300000875045us-gaap:ProductAndServiceOtherMember2025-01-012025-06-300000875045us-gaap:ProductAndServiceOtherMember2024-01-012024-06-3000008750452025-04-012025-06-3000008750452024-04-012024-06-3000008750452024-01-012024-06-3000008750452025-06-3000008750452024-12-310000875045us-gaap:NonrelatedPartyMember2025-06-300000875045us-gaap:NonrelatedPartyMember2024-12-310000875045us-gaap:RelatedPartyMember2025-06-300000875045us-gaap:RelatedPartyMember2024-12-310000875045us-gaap:NonrelatedPartyMember2025-01-012025-06-300000875045us-gaap:NonrelatedPartyMember2024-01-012024-06-300000875045us-gaap:RelatedPartyMember2025-01-012025-06-300000875045us-gaap:RelatedPartyMember2024-01-012024-06-3000008750452023-12-3100008750452024-06-300000875045us-gaap:PreferredStockMember2025-03-310000875045us-gaap:CommonStockMember2025-03-310000875045us-gaap:AdditionalPaidInCapitalMember2025-03-310000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2025-03-310000875045us-gaap:RetainedEarningsMember2025-03-310000875045us-gaap:TreasuryStockCommonMember2025-03-3100008750452025-03-310000875045us-gaap:RetainedEarningsMember2025-04-012025-06-300000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2025-04-012025-06-300000875045us-gaap:CommonStockMember2025-04-012025-06-300000875045us-gaap:AdditionalPaidInCapitalMember2025-04-012025-06-300000875045us-gaap:PreferredStockMember2025-06-300000875045us-gaap:CommonStockMember2025-06-300000875045us-gaap:AdditionalPaidInCapitalMember2025-06-300000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2025-06-300000875045us-gaap:RetainedEarningsMember2025-06-300000875045us-gaap:TreasuryStockCommonMember2025-06-300000875045us-gaap:PreferredStockMember2024-12-310000875045us-gaap:CommonStockMember2024-12-310000875045us-gaap:AdditionalPaidInCapitalMember2024-12-310000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-12-310000875045us-gaap:RetainedEarningsMember2024-12-310000875045us-gaap:TreasuryStockCommonMember2024-12-310000875045us-gaap:RetainedEarningsMember2025-01-012025-06-300000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2025-01-012025-06-300000875045us-gaap:CommonStockMember2025-01-012025-06-300000875045us-gaap:AdditionalPaidInCapitalMember2025-01-012025-06-300000875045us-gaap:PreferredStockMember2024-03-310000875045us-gaap:CommonStockMember2024-03-310000875045us-gaap:AdditionalPaidInCapitalMember2024-03-310000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-03-310000875045us-gaap:RetainedEarningsMember2024-03-310000875045us-gaap:TreasuryStockCommonMember2024-03-3100008750452024-03-310000875045us-gaap:RetainedEarningsMember2024-04-012024-06-300000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-04-012024-06-300000875045us-gaap:CommonStockMember2024-04-012024-06-300000875045us-gaap:AdditionalPaidInCapitalMember2024-04-012024-06-300000875045us-gaap:PreferredStockMember2024-06-300000875045us-gaap:CommonStockMember2024-06-300000875045us-gaap:AdditionalPaidInCapitalMember2024-06-300000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-06-300000875045us-gaap:RetainedEarningsMember2024-06-300000875045us-gaap:TreasuryStockCommonMember2024-06-300000875045us-gaap:PreferredStockMember2023-12-310000875045us-gaap:CommonStockMember2023-12-310000875045us-gaap:AdditionalPaidInCapitalMember2023-12-310000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2023-12-310000875045us-gaap:RetainedEarningsMember2023-12-310000875045us-gaap:TreasuryStockCommonMember2023-12-310000875045us-gaap:ParentMember2023-12-310000875045us-gaap:RetainedEarningsMember2024-01-012024-06-300000875045us-gaap:ParentMember2024-01-012024-06-300000875045us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-01-012024-06-300000875045us-gaap:CommonStockMember2024-01-012024-06-300000875045us-gaap:AdditionalPaidInCapitalMember2024-01-012024-06-300000875045us-gaap:ParentMember2024-06-300000875045biib:HumanImmunologyBiosciencesMembersrt:ScenarioPreviouslyReportedMember2024-07-022024-07-020000875045biib:HumanImmunologyBiosciencesMember2024-07-020000875045biib:HumanImmunologyBiosciencesMember2024-07-022024-07-020000875045biib:HumanImmunologyBiosciencesMemberus-gaap:ResearchAndDevelopmentExpenseMember2024-07-022024-07-020000875045biib:HumanImmunologyBiosciencesMemberus-gaap:SellingGeneralAndAdministrativeExpensesMember2024-07-022024-07-020000875045biib:HumanImmunologyBiosciencesMembersrt:MinimumMemberus-gaap:MeasurementInputDiscountRateMember2024-07-020000875045biib:HumanImmunologyBiosciencesMembersrt:MaximumMemberus-gaap:MeasurementInputDiscountRateMember2024-07-020000875045biib:HumanImmunologyBiosciencesMemberbiib:MeasurementInputProbabilityRateMember2024-07-020000875045biib:Phase3ClinicalTrialFelzartamabOneMemberbiib:HumanImmunologyBiosciencesMembersrt:MaximumMember2024-07-020000875045biib:Phase3ClinicalTrialFelzartamabTwoMemberbiib:HumanImmunologyBiosciencesMembersrt:MaximumMember2024-07-020000875045biib:FelzartamabAndIzastobartHIB210Memberbiib:MilestonePaymentFutureDevelopmentMemberbiib:HumanImmunologyBiosciencesPreExistingInLicenseCommitmentsMember2025-06-300000875045biib:FelzartamabAndIzastobartHIB210Memberbiib:MilestonePaymentRegulatoryMemberbiib:HumanImmunologyBiosciencesPreExistingInLicenseCommitmentsMember2025-06-300000875045biib:FelzartamabAndIzastobartHIB210Memberbiib:MilestonePaymentCommercialMemberbiib:HumanImmunologyBiosciencesPreExistingInLicenseCommitmentsMember2025-06-300000875045biib:FelzartamabIgANMemberbiib:HumanImmunologyBiosciencesMemberus-gaap:InProcessResearchAndDevelopmentMember2024-07-020000875045biib:FelzartamabAMRMemberbiib:HumanImmunologyBiosciencesMemberus-gaap:InProcessResearchAndDevelopmentMember2024-07-020000875045biib:FelzartamabPMNMemberbiib:HumanImmunologyBiosciencesMemberus-gaap:InProcessResearchAndDevelopmentMember2024-07-020000875045biib:HumanImmunologyBiosciencesMemberbiib:OtherClinicalProgramsMember2024-07-020000875045biib:HumanImmunologyBiosciencesMember2025-01-012025-06-300000875045biib:FelzartamabIgANMemberbiib:HumanImmunologyBiosciencesMember2024-07-020000875045biib:FelzartamabAMRMemberbiib:HumanImmunologyBiosciencesMember2024-07-020000875045biib:FelzartamabPMNMemberbiib:HumanImmunologyBiosciencesMember2024-07-020000875045biib:HumanImmunologyBiosciencesMemberus-gaap:MeasurementInputDiscountRateMember2024-07-020000875045biib:HumanImmunologyBiosciencesMember2025-04-012025-06-300000875045biib:SamsungBiosimilarAgreementMember2022-03-310000875045biib:SamsungBiosimilarAgreementMember2022-04-012022-04-300000875045biib:SamsungBiosimilarAgreementMember2022-04-012022-04-300000875045biib:SamsungBiosimilarAgreementMember2022-04-300000875045biib:SamsungBiosimilarAgreementMemberbiib:PaymentDueAtFirstAnniversaryMember2022-04-300000875045biib:SamsungBiosimilarAgreementMemberbiib:PaymentDueAtSecondAnniversaryMember2022-04-300000875045biib:SamsungBiosimilarAgreementMemberbiib:PaymentDueAtSecondAnniversaryMember2025-04-012025-06-300000875045biib:SamsungBiosimilarAgreementMemberbiib:PaymentDueAtSecondAnniversaryMember2025-01-012025-06-3000008750452024-04-012024-04-300000875045biib:IonisPharmaceuticalsInc.Member2024-04-012024-04-3000008750452025-03-012025-03-310000875045biib:A2023CostSavingInitiativesMember2023-09-262023-09-260000875045biib:A2023CostSavingInitiativesMember2025-01-012025-06-300000875045srt:MinimumMember2023-07-310000875045srt:MaximumMember2023-07-310000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:A2023CostSavingInitiativesMember2025-04-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:A2023CostSavingInitiativesMember2024-04-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:A2023CostSavingInitiativesMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:A2023CostSavingInitiativesMember2024-04-012024-06-300000875045us-gaap:RestructuringChargesMemberbiib:A2023CostSavingInitiativesMember2025-04-012025-06-300000875045us-gaap:RestructuringChargesMemberbiib:A2023CostSavingInitiativesMember2024-04-012024-06-300000875045biib:A2023CostSavingInitiativesMember2025-04-012025-06-300000875045biib:A2023CostSavingInitiativesMember2024-04-012024-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:A2023CostSavingInitiativesMember2025-01-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:A2023CostSavingInitiativesMember2024-01-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:A2023CostSavingInitiativesMember2025-01-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:A2023CostSavingInitiativesMember2024-01-012024-06-300000875045us-gaap:RestructuringChargesMemberbiib:A2023CostSavingInitiativesMember2025-01-012025-06-300000875045us-gaap:RestructuringChargesMemberbiib:A2023CostSavingInitiativesMember2024-01-012024-06-300000875045biib:A2023CostSavingInitiativesMember2024-01-012024-06-300000875045srt:MinimumMemberbiib:ReataIntegrationMember2025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:ReataIntegrationMember2025-04-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:ReataIntegrationMember2024-04-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:ReataIntegrationMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:ReataIntegrationMember2024-04-012024-06-300000875045us-gaap:RestructuringChargesMemberbiib:ReataIntegrationMember2025-04-012025-06-300000875045us-gaap:RestructuringChargesMemberbiib:ReataIntegrationMember2024-04-012024-06-300000875045biib:ReataIntegrationMember2025-04-012025-06-300000875045biib:ReataIntegrationMember2024-04-012024-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:ReataIntegrationMember2025-01-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:ReataIntegrationMember2024-01-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:ReataIntegrationMember2025-01-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:ReataIntegrationMember2024-01-012024-06-300000875045us-gaap:RestructuringChargesMemberbiib:ReataIntegrationMember2025-01-012025-06-300000875045us-gaap:RestructuringChargesMemberbiib:ReataIntegrationMember2024-01-012024-06-300000875045biib:ReataIntegrationMember2025-01-012025-06-300000875045biib:ReataIntegrationMember2024-01-012024-06-300000875045biib:ReataPharmaceuticalsIncMember2023-09-300000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2024-12-310000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2023-12-310000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2025-01-012025-03-310000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2024-01-012024-03-310000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2025-03-310000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2024-03-310000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2025-04-012025-06-300000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2024-04-012024-06-300000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2025-06-300000875045us-gaap:EmployeeSeveranceMemberbiib:A2023And2022CostSavingInitiativesMember2024-06-300000875045biib:TECFIDERAMembercountry:US2025-04-012025-06-300000875045biib:TECFIDERAMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:TECFIDERAMember2025-04-012025-06-300000875045biib:TECFIDERAMembercountry:US2024-04-012024-06-300000875045biib:TECFIDERAMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:TECFIDERAMember2024-04-012024-06-300000875045biib:VUMERITYMembercountry:US2025-04-012025-06-300000875045biib:VUMERITYMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:VUMERITYMember2025-04-012025-06-300000875045biib:VUMERITYMembercountry:US2024-04-012024-06-300000875045biib:VUMERITYMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:VUMERITYMember2024-04-012024-06-300000875045biib:FumarateMembercountry:US2025-04-012025-06-300000875045biib:FumarateMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:FumarateMember2025-04-012025-06-300000875045biib:FumarateMembercountry:US2024-04-012024-06-300000875045biib:FumarateMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:FumarateMember2024-04-012024-06-300000875045biib:AVONEXMembercountry:US2025-04-012025-06-300000875045biib:AVONEXMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:AVONEXMember2025-04-012025-06-300000875045biib:AVONEXMembercountry:US2024-04-012024-06-300000875045biib:AVONEXMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:AVONEXMember2024-04-012024-06-300000875045biib:PLEGRIDYMembercountry:US2025-04-012025-06-300000875045biib:PLEGRIDYMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:PLEGRIDYMember2025-04-012025-06-300000875045biib:PLEGRIDYMembercountry:US2024-04-012024-06-300000875045biib:PLEGRIDYMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:PLEGRIDYMember2024-04-012024-06-300000875045biib:InterferonMembercountry:US2025-04-012025-06-300000875045biib:InterferonMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:InterferonMember2025-04-012025-06-300000875045biib:InterferonMembercountry:US2024-04-012024-06-300000875045biib:InterferonMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:InterferonMember2024-04-012024-06-300000875045biib:TysabriProductMembercountry:US2025-04-012025-06-300000875045biib:TysabriProductMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:TysabriProductMember2025-04-012025-06-300000875045biib:TysabriProductMembercountry:US2024-04-012024-06-300000875045biib:TysabriProductMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:TysabriProductMember2024-04-012024-06-300000875045biib:FAMPYRAMembercountry:US2025-04-012025-06-300000875045biib:FAMPYRAMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:FAMPYRAMember2025-04-012025-06-300000875045biib:FAMPYRAMembercountry:US2024-04-012024-06-300000875045biib:FAMPYRAMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:FAMPYRAMember2024-04-012024-06-300000875045biib:MSProductRevenuesMembercountry:US2025-04-012025-06-300000875045biib:MSProductRevenuesMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:MSProductRevenuesMember2025-04-012025-06-300000875045biib:MSProductRevenuesMembercountry:US2024-04-012024-06-300000875045biib:MSProductRevenuesMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:MSProductRevenuesMember2024-04-012024-06-300000875045biib:SPINRAZAMembercountry:US2025-04-012025-06-300000875045biib:SPINRAZAMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:SPINRAZAMember2025-04-012025-06-300000875045biib:SPINRAZAMembercountry:US2024-04-012024-06-300000875045biib:SPINRAZAMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:SPINRAZAMember2024-04-012024-06-300000875045biib:SKYCLARYSMembercountry:US2025-04-012025-06-300000875045biib:SKYCLARYSMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:SKYCLARYSMember2025-04-012025-06-300000875045biib:SKYCLARYSMembercountry:US2024-04-012024-06-300000875045biib:SKYCLARYSMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:SKYCLARYSMember2024-04-012024-06-300000875045biib:QALSODYMembercountry:US2025-04-012025-06-300000875045biib:QALSODYMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:QALSODYMember2025-04-012025-06-300000875045biib:QALSODYMembercountry:US2024-04-012024-06-300000875045biib:QALSODYMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:QALSODYMember2024-04-012024-06-300000875045biib:RareDiseaseProductRevenueMembercountry:US2025-04-012025-06-300000875045biib:RareDiseaseProductRevenueMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:RareDiseaseProductRevenueMember2025-04-012025-06-300000875045biib:RareDiseaseProductRevenueMembercountry:US2024-04-012024-06-300000875045biib:RareDiseaseProductRevenueMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:RareDiseaseProductRevenueMember2024-04-012024-06-300000875045biib:BENEPALIMembercountry:US2025-04-012025-06-300000875045biib:BENEPALIMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:BENEPALIMember2025-04-012025-06-300000875045biib:BENEPALIMembercountry:US2024-04-012024-06-300000875045biib:BENEPALIMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:BENEPALIMember2024-04-012024-06-300000875045biib:IMRALDIMembercountry:US2025-04-012025-06-300000875045biib:IMRALDIMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:IMRALDIMember2025-04-012025-06-300000875045biib:IMRALDIMembercountry:US2024-04-012024-06-300000875045biib:IMRALDIMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:IMRALDIMember2024-04-012024-06-300000875045biib:FLIXABIMembercountry:US2025-04-012025-06-300000875045biib:FLIXABIMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:FLIXABIMember2025-04-012025-06-300000875045biib:FLIXABIMembercountry:US2024-04-012024-06-300000875045biib:FLIXABIMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:FLIXABIMember2024-04-012024-06-300000875045biib:BYOOVIZMembercountry:US2025-04-012025-06-300000875045biib:BYOOVIZMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:BYOOVIZMember2025-04-012025-06-300000875045biib:BYOOVIZMembercountry:US2024-04-012024-06-300000875045biib:BYOOVIZMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:BYOOVIZMember2024-04-012024-06-300000875045biib:TOFIDENCEMembercountry:US2025-04-012025-06-300000875045biib:TOFIDENCEMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:TOFIDENCEMember2025-04-012025-06-300000875045biib:TOFIDENCEMembercountry:US2024-04-012024-06-300000875045biib:TOFIDENCEMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:TOFIDENCEMember2024-04-012024-06-300000875045biib:BiosimilarsMembercountry:US2025-04-012025-06-300000875045biib:BiosimilarsMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:BiosimilarsMember2025-04-012025-06-300000875045biib:BiosimilarsMembercountry:US2024-04-012024-06-300000875045biib:BiosimilarsMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:BiosimilarsMember2024-04-012024-06-300000875045biib:ZURZUVAEMembercountry:US2025-04-012025-06-300000875045biib:ZURZUVAEMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:ZURZUVAEMember2025-04-012025-06-300000875045biib:ZURZUVAEMembercountry:US2024-04-012024-06-300000875045biib:ZURZUVAEMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:ZURZUVAEMember2024-04-012024-06-300000875045biib:FUMADERMAndADUHELMMembercountry:US2025-04-012025-06-300000875045biib:FUMADERMAndADUHELMMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:FUMADERMAndADUHELMMember2025-04-012025-06-300000875045biib:FUMADERMAndADUHELMMembercountry:US2024-04-012024-06-300000875045biib:FUMADERMAndADUHELMMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:FUMADERMAndADUHELMMember2024-04-012024-06-300000875045biib:OtherProductsMembercountry:US2025-04-012025-06-300000875045biib:OtherProductsMemberus-gaap:NonUsMember2025-04-012025-06-300000875045biib:OtherProductsMember2025-04-012025-06-300000875045biib:OtherProductsMembercountry:US2024-04-012024-06-300000875045biib:OtherProductsMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:OtherProductsMember2024-04-012024-06-300000875045us-gaap:ProductMembercountry:US2025-04-012025-06-300000875045us-gaap:ProductMemberus-gaap:NonUsMember2025-04-012025-06-300000875045us-gaap:ProductMembercountry:US2024-04-012024-06-300000875045us-gaap:ProductMemberus-gaap:NonUsMember2024-04-012024-06-300000875045biib:TECFIDERAMembercountry:US2025-01-012025-06-300000875045biib:TECFIDERAMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:TECFIDERAMember2025-01-012025-06-300000875045biib:TECFIDERAMembercountry:US2024-01-012024-06-300000875045biib:TECFIDERAMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:TECFIDERAMember2024-01-012024-06-300000875045biib:VUMERITYMembercountry:US2025-01-012025-06-300000875045biib:VUMERITYMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:VUMERITYMember2025-01-012025-06-300000875045biib:VUMERITYMembercountry:US2024-01-012024-06-300000875045biib:VUMERITYMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:VUMERITYMember2024-01-012024-06-300000875045biib:FumarateMembercountry:US2025-01-012025-06-300000875045biib:FumarateMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:FumarateMember2025-01-012025-06-300000875045biib:FumarateMembercountry:US2024-01-012024-06-300000875045biib:FumarateMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:FumarateMember2024-01-012024-06-300000875045biib:AVONEXMembercountry:US2025-01-012025-06-300000875045biib:AVONEXMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:AVONEXMember2025-01-012025-06-300000875045biib:AVONEXMembercountry:US2024-01-012024-06-300000875045biib:AVONEXMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:AVONEXMember2024-01-012024-06-300000875045biib:PLEGRIDYMembercountry:US2025-01-012025-06-300000875045biib:PLEGRIDYMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:PLEGRIDYMember2025-01-012025-06-300000875045biib:PLEGRIDYMembercountry:US2024-01-012024-06-300000875045biib:PLEGRIDYMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:PLEGRIDYMember2024-01-012024-06-300000875045biib:InterferonMembercountry:US2025-01-012025-06-300000875045biib:InterferonMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:InterferonMember2025-01-012025-06-300000875045biib:InterferonMembercountry:US2024-01-012024-06-300000875045biib:InterferonMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:InterferonMember2024-01-012024-06-300000875045biib:TysabriProductMembercountry:US2025-01-012025-06-300000875045biib:TysabriProductMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:TysabriProductMember2025-01-012025-06-300000875045biib:TysabriProductMembercountry:US2024-01-012024-06-300000875045biib:TysabriProductMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:TysabriProductMember2024-01-012024-06-300000875045biib:FAMPYRAMembercountry:US2025-01-012025-06-300000875045biib:FAMPYRAMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:FAMPYRAMember2025-01-012025-06-300000875045biib:FAMPYRAMembercountry:US2024-01-012024-06-300000875045biib:FAMPYRAMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:FAMPYRAMember2024-01-012024-06-300000875045biib:MSProductRevenuesMembercountry:US2025-01-012025-06-300000875045biib:MSProductRevenuesMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:MSProductRevenuesMember2025-01-012025-06-300000875045biib:MSProductRevenuesMembercountry:US2024-01-012024-06-300000875045biib:MSProductRevenuesMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:MSProductRevenuesMember2024-01-012024-06-300000875045biib:SPINRAZAMembercountry:US2025-01-012025-06-300000875045biib:SPINRAZAMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:SPINRAZAMember2025-01-012025-06-300000875045biib:SPINRAZAMembercountry:US2024-01-012024-06-300000875045biib:SPINRAZAMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:SPINRAZAMember2024-01-012024-06-300000875045biib:SKYCLARYSMembercountry:US2025-01-012025-06-300000875045biib:SKYCLARYSMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:SKYCLARYSMember2025-01-012025-06-300000875045biib:SKYCLARYSMembercountry:US2024-01-012024-06-300000875045biib:SKYCLARYSMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:SKYCLARYSMember2024-01-012024-06-300000875045biib:QALSODYMembercountry:US2025-01-012025-06-300000875045biib:QALSODYMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:QALSODYMember2025-01-012025-06-300000875045biib:QALSODYMembercountry:US2024-01-012024-06-300000875045biib:QALSODYMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:QALSODYMember2024-01-012024-06-300000875045biib:RareDiseaseProductRevenueMembercountry:US2025-01-012025-06-300000875045biib:RareDiseaseProductRevenueMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:RareDiseaseProductRevenueMember2025-01-012025-06-300000875045biib:RareDiseaseProductRevenueMembercountry:US2024-01-012024-06-300000875045biib:RareDiseaseProductRevenueMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:RareDiseaseProductRevenueMember2024-01-012024-06-300000875045biib:BENEPALIMembercountry:US2025-01-012025-06-300000875045biib:BENEPALIMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:BENEPALIMember2025-01-012025-06-300000875045biib:BENEPALIMembercountry:US2024-01-012024-06-300000875045biib:BENEPALIMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:BENEPALIMember2024-01-012024-06-300000875045biib:IMRALDIMembercountry:US2025-01-012025-06-300000875045biib:IMRALDIMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:IMRALDIMember2025-01-012025-06-300000875045biib:IMRALDIMembercountry:US2024-01-012024-06-300000875045biib:IMRALDIMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:IMRALDIMember2024-01-012024-06-300000875045biib:FLIXABIMembercountry:US2025-01-012025-06-300000875045biib:FLIXABIMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:FLIXABIMember2025-01-012025-06-300000875045biib:FLIXABIMembercountry:US2024-01-012024-06-300000875045biib:FLIXABIMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:FLIXABIMember2024-01-012024-06-300000875045biib:BYOOVIZMembercountry:US2025-01-012025-06-300000875045biib:BYOOVIZMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:BYOOVIZMember2025-01-012025-06-300000875045biib:BYOOVIZMembercountry:US2024-01-012024-06-300000875045biib:BYOOVIZMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:BYOOVIZMember2024-01-012024-06-300000875045biib:TOFIDENCEMembercountry:US2025-01-012025-06-300000875045biib:TOFIDENCEMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:TOFIDENCEMember2025-01-012025-06-300000875045biib:TOFIDENCEMembercountry:US2024-01-012024-06-300000875045biib:TOFIDENCEMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:TOFIDENCEMember2024-01-012024-06-300000875045biib:BiosimilarsMembercountry:US2025-01-012025-06-300000875045biib:BiosimilarsMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:BiosimilarsMember2025-01-012025-06-300000875045biib:BiosimilarsMembercountry:US2024-01-012024-06-300000875045biib:BiosimilarsMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:BiosimilarsMember2024-01-012024-06-300000875045biib:ZURZUVAEMembercountry:US2025-01-012025-06-300000875045biib:ZURZUVAEMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:ZURZUVAEMember2025-01-012025-06-300000875045biib:ZURZUVAEMembercountry:US2024-01-012024-06-300000875045biib:ZURZUVAEMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:ZURZUVAEMember2024-01-012024-06-300000875045biib:FUMADERMAndADUHELMMembercountry:US2025-01-012025-06-300000875045biib:FUMADERMAndADUHELMMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:FUMADERMAndADUHELMMember2025-01-012025-06-300000875045biib:FUMADERMAndADUHELMMembercountry:US2024-01-012024-06-300000875045biib:FUMADERMAndADUHELMMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:FUMADERMAndADUHELMMember2024-01-012024-06-300000875045biib:OtherProductsMembercountry:US2025-01-012025-06-300000875045biib:OtherProductsMemberus-gaap:NonUsMember2025-01-012025-06-300000875045biib:OtherProductsMember2025-01-012025-06-300000875045biib:OtherProductsMembercountry:US2024-01-012024-06-300000875045biib:OtherProductsMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:OtherProductsMember2024-01-012024-06-300000875045us-gaap:ProductMembercountry:US2025-01-012025-06-300000875045us-gaap:ProductMemberus-gaap:NonUsMember2025-01-012025-06-300000875045us-gaap:ProductMembercountry:US2024-01-012024-06-300000875045us-gaap:ProductMemberus-gaap:NonUsMember2024-01-012024-06-300000875045biib:DistributorOneMember2025-04-012025-06-300000875045biib:DistributorTwoMember2025-04-012025-06-300000875045biib:DistributorOneMember2025-01-012025-06-300000875045biib:DistributorTwoMember2025-01-012025-06-300000875045biib:DistributorOneMember2024-04-012024-06-300000875045biib:DistributorTwoMember2024-04-012024-06-300000875045biib:DistributorOneMember2024-01-012024-06-300000875045biib:DistributorTwoMember2024-01-012024-06-300000875045biib:ReserveforCashDiscountsMember2024-12-310000875045biib:ContractualAdjustmentsMember2024-12-310000875045us-gaap:SalesReturnsAndAllowancesMember2024-12-310000875045biib:ReserveforCashDiscountsMember2025-01-012025-06-300000875045biib:ContractualAdjustmentsMember2025-01-012025-06-300000875045us-gaap:SalesReturnsAndAllowancesMember2025-01-012025-06-300000875045biib:ReserveforCashDiscountsMember2025-06-300000875045biib:ContractualAdjustmentsMember2025-06-300000875045us-gaap:SalesReturnsAndAllowancesMember2025-06-300000875045us-gaap:AccountsReceivableMember2025-06-300000875045us-gaap:AccountsReceivableMember2024-12-310000875045us-gaap:OtherCurrentLiabilitiesMember2025-06-300000875045us-gaap:OtherCurrentLiabilitiesMember2024-12-310000875045biib:RoyaltyAttributedToOCREVUSMember2025-04-012025-06-300000875045biib:RoyaltyAttributedToOCREVUSMember2024-04-012024-06-300000875045biib:RoyaltyAttributedToOCREVUSMember2025-01-012025-06-300000875045biib:RoyaltyAttributedToOCREVUSMember2024-01-012024-06-300000875045biib:RocheGroupGenentechMember2025-04-012025-06-300000875045biib:RocheGroupGenentechMember2024-04-012024-06-300000875045biib:RocheGroupGenentechMember2025-01-012025-06-300000875045biib:RocheGroupGenentechMember2024-01-012024-06-300000875045biib:LEQEMBICollaborationMember2025-06-300000875045biib:AlzheimersCollaborationMember2025-04-012025-06-300000875045biib:AlzheimersCollaborationMember2025-01-012025-06-300000875045biib:AlzheimersCollaborationMember2024-04-012024-06-300000875045biib:AlzheimersCollaborationMember2024-01-012024-06-300000875045biib:ContractManufacturingAndOtherRevenueMember2025-04-012025-06-300000875045biib:ContractManufacturingAndOtherRevenueMember2024-04-012024-06-300000875045biib:ContractManufacturingAndOtherRevenueMember2025-01-012025-06-300000875045biib:ContractManufacturingAndOtherRevenueMember2024-01-012024-06-300000875045us-gaap:RoyaltyMember2025-04-012025-06-300000875045us-gaap:RoyaltyMember2024-04-012024-06-300000875045us-gaap:RoyaltyMember2025-01-012025-06-300000875045us-gaap:RoyaltyMember2024-01-012024-06-300000875045biib:ReataPharmaceuticalsIncMember2023-09-260000875045biib:ReataPharmaceuticalsIncMemberus-gaap:FairValueAdjustmentToInventoryMember2025-04-012025-06-300000875045biib:ReataPharmaceuticalsIncMemberus-gaap:FairValueAdjustmentToInventoryMember2025-01-012025-06-300000875045biib:ReataPharmaceuticalsIncMemberus-gaap:FairValueAdjustmentToInventoryMember2024-04-012024-06-300000875045biib:ReataPharmaceuticalsIncMemberus-gaap:FairValueAdjustmentToInventoryMember2024-01-012024-06-300000875045biib:ClinicalInventoryMemberbiib:ReataPharmaceuticalsIncMemberus-gaap:FairValueAdjustmentToInventoryMember2024-01-012024-06-300000875045srt:MinimumMember2025-06-300000875045srt:MaximumMember2025-06-300000875045us-gaap:InProcessResearchAndDevelopmentMember2025-06-300000875045us-gaap:InProcessResearchAndDevelopmentMember2024-12-310000875045biib:PriorityReviewVoucherMember2025-06-300000875045biib:PriorityReviewVoucherMember2024-12-310000875045us-gaap:TrademarksAndTradeNamesMember2025-06-300000875045us-gaap:TrademarksAndTradeNamesMember2024-12-310000875045biib:AcquiredAndInLicensedRightsAndPatentsMember2025-06-300000875045biib:HumanImmunologyBiosciencesMemberus-gaap:InProcessResearchAndDevelopmentMember2024-12-310000875045biib:HumanImmunologyBiosciencesMemberus-gaap:InProcessResearchAndDevelopmentMember2025-06-300000875045biib:ReataPharmaceuticalsIncMemberbiib:PriorityReviewVoucherMember2023-09-300000875045us-gaap:FairValueMeasurementsRecurringMember2025-06-300000875045us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel1Member2025-06-300000875045us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2025-06-300000875045us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2025-06-300000875045us-gaap:FairValueMeasurementsRecurringMember2024-12-310000875045us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel1Member2024-12-310000875045us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2024-12-310000875045us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2024-12-310000875045us-gaap:FairValueInputsLevel3Member2025-06-300000875045us-gaap:FairValueInputsLevel3Membersrt:MinimumMemberus-gaap:MeasurementInputDiscountRateMember2025-06-300000875045us-gaap:FairValueInputsLevel3Membersrt:MaximumMemberus-gaap:MeasurementInputDiscountRateMember2025-06-300000875045us-gaap:FairValueInputsLevel3Membersrt:WeightedAverageMemberus-gaap:MeasurementInputDiscountRateMember2025-06-300000875045us-gaap:FairValueInputsLevel3Member2024-12-310000875045us-gaap:FairValueInputsLevel3Membersrt:MinimumMemberus-gaap:MeasurementInputDiscountRateMember2024-12-310000875045us-gaap:FairValueInputsLevel3Membersrt:MaximumMemberus-gaap:MeasurementInputDiscountRateMember2024-12-310000875045us-gaap:FairValueInputsLevel3Membersrt:WeightedAverageMemberus-gaap:MeasurementInputDiscountRateMember2024-12-310000875045biib:HumanImmunologyBiosciencesMemberbiib:MeasurementInputProbabilityRateMember2025-06-300000875045biib:SeniorNotesFourPointZeroFivePercentDueTwentyTwentyFiveMember2025-06-300000875045biib:SeniorNotesFourPointZeroFivePercentDueTwentyTwentyFiveMemberus-gaap:SeniorNotesMember2025-06-300000875045biib:SeniorNotesFourPointZeroFivePercentDueTwentyTwentyFiveMemberus-gaap:SeniorNotesMember2024-12-310000875045us-gaap:SeniorNotesMember2025-06-300000875045us-gaap:SeniorNotesMember2024-12-310000875045biib:A2.25SeniorNotesdueMay12030Member2025-06-300000875045biib:A2.25SeniorNotesdueMay12030Memberus-gaap:SeniorNotesMember2025-06-300000875045biib:A2.25SeniorNotesdueMay12030Member2024-12-310000875045biib:A2.25SeniorNotesdueMay12030Memberus-gaap:SeniorNotesMember2024-12-310000875045biib:A5.050SeniorNotesDueJanuary152031Member2025-06-300000875045biib:A5.050SeniorNotesDueJanuary152031Memberus-gaap:SeniorNotesMember2025-06-300000875045biib:A5.050SeniorNotesDueJanuary152031Member2024-12-310000875045biib:A5.050SeniorNotesDueJanuary152031Memberus-gaap:SeniorNotesMember2024-12-310000875045biib:A5.750SeniorNotesDueMay152035Member2025-06-300000875045biib:A5.750SeniorNotesDueMay152035Memberus-gaap:SeniorNotesMember2025-06-300000875045biib:A5.750SeniorNotesDueMay152035Member2024-12-310000875045biib:A5.750SeniorNotesDueMay152035Memberus-gaap:SeniorNotesMember2024-12-310000875045biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFiveMember2025-06-300000875045biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFiveMemberus-gaap:SeniorNotesMember2025-06-300000875045biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFiveMember2024-12-310000875045biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFiveMemberus-gaap:SeniorNotesMember2024-12-310000875045biib:A3.15SeniorNotesdueMay12050Member2025-06-300000875045biib:A3.15SeniorNotesdueMay12050Memberus-gaap:SeniorNotesMember2025-06-300000875045biib:A3.15SeniorNotesdueMay12050Member2024-12-310000875045biib:A3.15SeniorNotesdueMay12050Memberus-gaap:SeniorNotesMember2024-12-310000875045biib:SeniorNotes3.250DueFebruary152051Member2025-06-300000875045biib:SeniorNotes3.250DueFebruary152051Memberus-gaap:SeniorNotesMember2025-06-300000875045biib:SeniorNotes3.250DueFebruary152051Member2024-12-310000875045biib:SeniorNotes3.250DueFebruary152051Memberus-gaap:SeniorNotesMember2024-12-310000875045biib:A6.450SeniorNotesDueMay152055Member2025-06-300000875045biib:A6.450SeniorNotesDueMay152055Memberus-gaap:SeniorNotesMember2025-06-300000875045biib:A6.450SeniorNotesDueMay152055Member2024-12-310000875045biib:A6.450SeniorNotesDueMay152055Memberus-gaap:SeniorNotesMember2024-12-310000875045biib:NonCurrentPortionOfNotesPayableAndTermLoanMemberus-gaap:SeniorNotesMember2025-06-300000875045biib:NonCurrentPortionOfNotesPayableAndTermLoanMemberus-gaap:SeniorNotesMember2024-12-310000875045us-gaap:SeniorNotesMember2025-05-120000875045us-gaap:MoneyMarketFundsMember2025-06-300000875045us-gaap:MoneyMarketFundsMember2024-12-310000875045biib:EquitySecuritiesNonCurrentMember2025-06-300000875045biib:EquitySecuritiesNonCurrentMember2024-12-310000875045biib:StrategicInvestmentsMemberus-gaap:OtherNoncurrentAssetsMember2025-06-300000875045biib:StrategicInvestmentsMemberus-gaap:OtherNoncurrentAssetsMember2024-12-310000875045srt:MinimumMember2024-12-310000875045srt:MaximumMember2024-12-310000875045us-gaap:ForeignExchangeContractMembercurrency:EURus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:ForeignExchangeContractMembercurrency:EURus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:ForeignExchangeContractMembercurrency:GBPus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:ForeignExchangeContractMembercurrency:GBPus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:ForeignExchangeContractMembercurrency:CHFus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:ForeignExchangeContractMembercurrency:CHFus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:ForeignExchangeContractMembercurrency:CADus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:ForeignExchangeContractMembercurrency:CADus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:ForeignExchangeContractMemberus-gaap:SalesMember2025-04-012025-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:SalesMember2024-04-012024-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsrevenueMemberus-gaap:SalesMember2025-04-012025-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsrevenueMemberus-gaap:SalesMember2024-04-012024-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:OperatingExpenseMember2025-04-012025-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:OperatingExpenseMember2024-04-012024-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsoperatingexpensesMemberus-gaap:OperatingExpenseMember2025-04-012025-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsoperatingexpensesMemberus-gaap:OperatingExpenseMember2024-04-012024-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:SalesMember2025-01-012025-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:SalesMember2024-01-012024-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsrevenueMemberus-gaap:SalesMember2025-01-012025-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsrevenueMemberus-gaap:SalesMember2024-01-012024-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:OperatingExpenseMember2025-01-012025-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:OperatingExpenseMember2024-01-012024-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsoperatingexpensesMemberus-gaap:OperatingExpenseMember2025-01-012025-06-300000875045us-gaap:ForeignExchangeContractMemberbiib:CashflowsoperatingexpensesMemberus-gaap:OperatingExpenseMember2024-01-012024-06-300000875045us-gaap:NondesignatedMember2025-06-300000875045us-gaap:NondesignatedMember2024-12-310000875045us-gaap:OtherCurrentAssetsMemberus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:OtherCurrentAssetsMemberus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:AccruedLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMember2025-06-300000875045us-gaap:AccruedLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMember2024-12-310000875045us-gaap:ForeignExchangeContractMemberus-gaap:OtherNoncurrentLiabilitiesMemberus-gaap:CashFlowHedgingMember2025-06-300000875045us-gaap:ForeignExchangeContractMemberus-gaap:OtherNoncurrentLiabilitiesMemberus-gaap:CashFlowHedgingMember2024-12-310000875045us-gaap:OtherCurrentAssetsMemberus-gaap:NondesignatedMember2025-06-300000875045us-gaap:OtherCurrentAssetsMemberus-gaap:NondesignatedMember2024-12-310000875045us-gaap:AccruedLiabilitiesMemberus-gaap:NondesignatedMember2025-06-300000875045us-gaap:AccruedLiabilitiesMemberus-gaap:NondesignatedMember2024-12-310000875045biib:HeadquartersLeaseFiveYearRenewalOptionMemberus-gaap:BuildingMember2025-03-012025-03-310000875045biib:HeadquartersLeaseFiveYearRenewalOptionMemberus-gaap:BuildingMember2025-03-310000875045biib:HeadquartersLeaseSixMonthRenewalOptionMemberus-gaap:BuildingMember2025-03-012025-03-310000875045biib:HeadquartersLeaseSixMonthRenewalOptionMemberus-gaap:BuildingMember2025-03-310000875045biib:A5.050SeniorNotesDueJanuary152031Memberus-gaap:SeniorNotesMember2025-05-120000875045biib:A5.750SeniorNotesDueMay152035Memberus-gaap:SeniorNotesMember2025-05-120000875045biib:A6.450SeniorNotesDueMay152055Memberus-gaap:SeniorNotesMember2025-05-120000875045biib:A2025SeniorNotesMemberus-gaap:SeniorNotesMember2025-01-012025-06-300000875045biib:SeniorNotesFourPointZeroFivePercentDueTwentyTwentyFiveMemberus-gaap:SeniorNotesMember2015-09-150000875045biib:SeniorNotesFourPointZeroFivePercentDueTwentyTwentyFiveMemberus-gaap:SeniorNotesMember2025-01-012025-06-300000875045biib:TheCreditFacilityMemberus-gaap:LineOfCreditMember2023-09-300000875045us-gaap:SecuredDebtMemberbiib:ReataPharmaceuticalsIncMemberbiib:TheCreditFacilityMemberus-gaap:LineOfCreditMember2023-09-300000875045biib:TheCreditFacilityFloatingRate364DayTrancheMemberus-gaap:LineOfCreditMember2023-09-300000875045biib:TheCreditFacilityFloatingRateThreeYearTrancheMemberus-gaap:LineOfCreditMember2023-09-300000875045biib:TheCreditFacilityTerminatedMemberus-gaap:LineOfCreditMember2023-09-300000875045biib:FloatingRate364DayTrancheMemberbiib:A2023TermLoanMemberus-gaap:LineOfCreditMember2024-01-012024-03-310000875045biib:FloatingRate364DayTrancheMemberbiib:A2023TermLoanMemberus-gaap:LineOfCreditMember2024-06-300000875045biib:FloatingRate364DayTrancheMemberbiib:TheCreditFacilityFloatingRateThreeYearTrancheMemberus-gaap:LineOfCreditMember2024-06-300000875045biib:TermLoan2023ThreeYearTrancheMemberbiib:A2023TermLoanMemberus-gaap:LineOfCreditMember2024-06-300000875045biib:A2020ShareRepurchaseProgramMember2020-10-310000875045biib:A2020ShareRepurchaseProgramMember2025-06-300000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2025-03-310000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2025-03-310000875045us-gaap:AccumulatedTranslationAdjustmentMember2025-03-310000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2025-04-012025-06-300000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2025-04-012025-06-300000875045us-gaap:AccumulatedTranslationAdjustmentMember2025-04-012025-06-300000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2025-06-300000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2025-06-300000875045us-gaap:AccumulatedTranslationAdjustmentMember2025-06-300000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-12-310000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2024-12-310000875045us-gaap:AccumulatedTranslationAdjustmentMember2024-12-310000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2025-01-012025-06-300000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2025-01-012025-06-300000875045us-gaap:AccumulatedTranslationAdjustmentMember2025-01-012025-06-300000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-03-310000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2024-03-310000875045us-gaap:AccumulatedTranslationAdjustmentMember2024-03-310000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-04-012024-06-300000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2024-04-012024-06-300000875045us-gaap:AccumulatedTranslationAdjustmentMember2024-04-012024-06-300000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-06-300000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2024-06-300000875045us-gaap:AccumulatedTranslationAdjustmentMember2024-06-300000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2023-12-310000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2023-12-310000875045us-gaap:AccumulatedTranslationAdjustmentMember2023-12-310000875045us-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-01-012024-06-300000875045us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2024-01-012024-06-300000875045us-gaap:AccumulatedTranslationAdjustmentMember2024-01-012024-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2025-04-012025-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-04-012024-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2025-01-012025-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedGainLossNetCashFlowHedgeParentMember2024-01-012024-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2025-04-012025-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2024-04-012024-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2025-01-012025-06-300000875045us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2024-01-012024-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2025-04-012025-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2024-04-012024-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2025-01-012025-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2024-01-012024-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2025-04-012025-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2024-04-012024-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2025-01-012025-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2024-01-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMember2024-04-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMember2025-01-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMember2024-01-012024-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMember2025-04-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMember2024-04-012024-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMember2025-01-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMember2024-01-012024-06-300000875045us-gaap:ParentMember2025-04-012025-06-300000875045us-gaap:ParentMember2024-04-012024-06-300000875045us-gaap:ParentMember2025-01-012025-06-300000875045us-gaap:ParentMember2024-01-012024-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2025-04-012025-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2024-04-012024-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2025-01-012025-06-300000875045biib:TimeVestedRestrictedStockUnitsMember2024-01-012024-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2025-04-012025-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2024-04-012024-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2025-01-012025-06-300000875045biib:PerformanceStockUnitsSettledinStockMember2024-01-012024-06-300000875045biib:EmployeeStockPurchasePlanMember2025-04-012025-06-300000875045biib:EmployeeStockPurchasePlanMember2024-04-012024-06-300000875045biib:EmployeeStockPurchasePlanMember2025-01-012025-06-300000875045biib:EmployeeStockPurchasePlanMember2024-01-012024-06-300000875045biib:PerformanceStockUnitsSettledinCashMember2025-04-012025-06-300000875045biib:PerformanceStockUnitsSettledinCashMember2024-04-012024-06-300000875045biib:PerformanceStockUnitsSettledinCashMember2025-01-012025-06-300000875045biib:PerformanceStockUnitsSettledinCashMember2024-01-012024-06-300000875045us-gaap:EmployeeStockOptionMember2025-04-012025-06-300000875045us-gaap:EmployeeStockOptionMember2024-04-012024-06-300000875045us-gaap:EmployeeStockOptionMember2025-01-012025-06-300000875045us-gaap:EmployeeStockOptionMember2024-01-012024-06-300000875045biib:MarketStockUnitsMember2025-04-012025-06-300000875045biib:MarketStockUnitsMember2024-04-012024-06-300000875045biib:MarketStockUnitsMember2025-01-012025-06-300000875045biib:MarketStockUnitsMember2024-01-012024-06-300000875045biib:SageAndDenaliMember2025-04-012025-06-300000875045biib:SageAndSangamoMember2024-04-012024-06-300000875045biib:DenaliTherapeuticsIncMember2024-04-012024-06-300000875045biib:DenaliTherapeuticsIncMember2025-01-012025-06-300000875045biib:SageTherapeuticsIncMember2025-01-012025-06-300000875045biib:SageAndSangamoMember2024-01-012024-06-300000875045biib:DenaliTherapeuticsIncMember2024-01-012024-06-300000875045biib:OCREVUSMembersrt:MinimumMember2017-03-012017-03-310000875045biib:OCREVUSMembersrt:MaximumMember2017-03-012017-03-310000875045biib:OCREVUSMember2017-03-012017-03-310000875045biib:OCREVUSMemberus-gaap:ForeignCountryMember2017-03-012017-03-310000875045biib:RituxanMember2025-06-300000875045biib:LUNSUMIOMember2025-06-300000875045biib:LUNSUMIOMember2025-01-012025-06-300000875045biib:GAZYVAMember2025-06-300000875045biib:IonisPharmaceuticalsInc.Member2025-06-300000875045biib:LEQEMBIMemberbiib:LEQEMBICollaborationMember2025-04-012025-06-300000875045biib:LEQEMBIMemberbiib:LEQEMBICollaborationMember2024-04-012024-06-300000875045biib:E2609andBAN2401Memberbiib:EisaiMember2025-01-012025-06-300000875045biib:E2609andBAN2401Memberbiib:EisaiMember2024-01-012024-06-300000875045biib:LEQEMBIMemberbiib:LEQEMBICollaborationMemberus-gaap:SellingGeneralAndAdministrativeExpensesMember2025-04-012025-06-300000875045biib:LEQEMBIMemberbiib:LEQEMBICollaborationMemberus-gaap:SellingGeneralAndAdministrativeExpensesMember2024-04-012024-06-300000875045biib:E2609andBAN2401Memberbiib:EisaiMemberus-gaap:SellingGeneralAndAdministrativeExpensesMember2025-01-012025-06-300000875045biib:E2609andBAN2401Memberbiib:EisaiMemberus-gaap:SellingGeneralAndAdministrativeExpensesMember2024-01-012024-06-300000875045biib:EisaiMember2025-06-300000875045biib:EisaiMember2024-12-310000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:UCBPharmaSAMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:UCBPharmaSAMember2024-04-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:UCBPharmaSAMember2025-01-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:UCBPharmaSAMember2024-01-012024-06-300000875045srt:ScenarioForecastMemberbiib:SageTherapeuticsIncMember2025-12-310000875045biib:SageTherapeuticsIncMember2025-04-012025-06-300000875045biib:SageTherapeuticsIncMember2025-01-012025-06-300000875045biib:SageTherapeuticsIncMember2024-04-012024-06-300000875045biib:SageTherapeuticsIncMember2024-01-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:SageTherapeuticsIncMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:SageTherapeuticsIncMember2024-04-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:SageTherapeuticsIncMember2025-01-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:SageTherapeuticsIncMember2024-01-012024-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:SageTherapeuticsIncMember2025-04-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:SageTherapeuticsIncMember2024-04-012024-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:SageTherapeuticsIncMember2025-01-012025-06-300000875045us-gaap:SellingGeneralAndAdministrativeExpensesMemberbiib:SageTherapeuticsIncMember2024-01-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:DenaliTherapeuticsIncMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:DenaliTherapeuticsIncMember2024-04-012024-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:DenaliTherapeuticsIncMember2025-01-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:DenaliTherapeuticsIncMember2024-01-012024-06-300000875045biib:ZorevunersenMemberbiib:StokeTherapeuticsIncMember2025-02-012025-02-280000875045biib:ZorevunersenMember2025-02-012025-02-280000875045biib:StokeTherapeuticsIncMember2025-02-012025-02-280000875045biib:MilestonePaymentDevelopmentalMemberbiib:StokeTherapeuticsIncMember2025-06-300000875045biib:MilestonePaymentCommercialMemberbiib:StokeTherapeuticsIncMember2025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:StokeTherapeuticsIncMember2025-04-012025-06-300000875045us-gaap:ResearchAndDevelopmentExpenseMemberbiib:StokeTherapeuticsIncMember2025-01-012025-06-300000875045biib:SamsungBiosimilarAgreementMember2019-12-012019-12-310000875045biib:SamsungBiosimilarAgreementMember2024-01-012024-12-310000875045biib:SamsungBiosimilarAgreementMember2024-12-310000875045biib:SamsungBiosimilarAgreementMember2025-01-012025-06-300000875045biib:SamsungBiosimilarAgreementMember2025-04-012025-06-300000875045biib:SamsungBiosimilarAgreementMember2025-01-012025-06-300000875045biib:SamsungBiosimilarAgreementMember2024-04-012024-06-300000875045biib:SamsungBiosimilarAgreementMember2024-01-012024-06-300000875045biib:SamsungBiosimilarAgreementMemberus-gaap:RelatedPartyMember2025-06-300000875045biib:SamsungBiosimilarAgreementMemberus-gaap:RelatedPartyMember2024-12-310000875045us-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember2025-02-110000875045biib:MilestonePaymentFutureDevelopmentMember2025-06-300000875045biib:FelzartamabAndIzastobartHIB210Memberbiib:MilestonePaymentOneMemberbiib:HumanImmunologyBiosciencesPreExistingInLicenseCommitmentsMember2025-06-300000875045biib:FelzartamabAndIzastobartHIB210Memberbiib:MilestonePaymentTwoMemberbiib:HumanImmunologyBiosciencesPreExistingInLicenseCommitmentsMember2025-06-300000875045biib:CityTherapeuticsInc.Memberus-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember2025-01-012025-06-300000875045biib:CityTherapeuticsInc.Memberus-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember2025-04-012025-06-300000875045biib:CityTherapeuticsInc.Memberus-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember2025-06-300000875045biib:MilestonePaymentResearchMemberus-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMemberbiib:CityTherapeuticsInc.Member2025-06-300000875045biib:MilestonePaymentDevelopmentalMemberus-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMemberbiib:CityTherapeuticsInc.Member2025-06-300000875045biib:MilestonePaymentSalesBasedMemberus-gaap:CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMemberbiib:CityTherapeuticsInc.Member2025-06-300000875045biib:IMRALDIPatentLitigationMember2022-06-012022-06-300000875045biib:ConvergenceMember2020-12-310000875045biib:ConvergenceMember2024-09-300000875045biib:GenentechMember2023-02-012023-02-280000875045biib:ReportableSegmentMember2025-04-012025-06-300000875045biib:ReportableSegmentMember2024-04-012024-06-300000875045biib:ReportableSegmentMember2025-01-012025-06-300000875045biib:ReportableSegmentMember2024-01-012024-06-300000875045us-gaap:ProductMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045us-gaap:ProductMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045us-gaap:ProductMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045us-gaap:ProductMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045us-gaap:RoyaltyMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045us-gaap:RoyaltyMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045us-gaap:RoyaltyMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045us-gaap:RoyaltyMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045biib:ResearchAndDiscoveryMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045biib:ResearchAndDiscoveryMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045biib:ResearchAndDiscoveryMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045biib:ResearchAndDiscoveryMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045biib:EarlyStageProgramsMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045biib:EarlyStageProgramsMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045biib:EarlyStageProgramsMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045biib:EarlyStageProgramsMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045biib:LateStageProgramsMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045biib:LateStageProgramsMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045biib:LateStageProgramsMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045biib:LateStageProgramsMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045biib:MarketedProductsMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045biib:MarketedProductsMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045biib:MarketedProductsMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045biib:MarketedProductsMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045us-gaap:ServiceOtherMemberbiib:ReportableSegmentMember2025-04-012025-06-300000875045us-gaap:ServiceOtherMemberbiib:ReportableSegmentMember2024-04-012024-06-300000875045us-gaap:ServiceOtherMemberbiib:ReportableSegmentMember2025-01-012025-06-300000875045us-gaap:ServiceOtherMemberbiib:ReportableSegmentMember2024-01-012024-06-300000875045biib:StephenSherwinMember2025-04-012025-06-300000875045biib:StephenSherwinMember2025-06-30

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-Q


☒			QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2025


☐			TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

Commission File Number 0-19311

BIOGEN INC.

(Exact name of registrant as specified in its charter)


Delaware						33-0112644
(State or other jurisdiction of incorporation or organization)						(I.R.S. Employer Identification No.)

225 Binney Street, Cambridge, MA 02142

(617) 679-2000

(Address, including zip code, and telephone number, including

area code, of registrant’s principal executive offices)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol(s)

Name of each exchange on which registered

Common Stock, $0.0005 par value

BIIB

The Nasdaq Global Select Market

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days: Yes x No o

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files): Yes x No o

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act:

Large accelerated filer

Accelerated filer

☐

Non-accelerated filer

☐

Smaller reporting company

☐

Emerging growth company

☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No x

The number of shares of the issuer’s Common Stock, $0.0005 par value, outstanding as of July 29, 2025, was 146,614,598 shares.

Table of Contents

BIOGEN INC.

FORM 10-Q — Quarterly Report

For the Quarterly Period Ended June 30, 2025

TABLE OF CONTENTS


		Page
PART I — FINANCIAL INFORMATION

Item 1.	Financial Statements (unaudited)

	Condensed Consolidated Statements of Income — For the Three and Six Months Ended June 30, 2025 and 2024	8

	Condensed Consolidated Statements of Comprehensive Income — For the Three and Six Months Ended June 30, 2025 and 2024	9

	Condensed Consolidated Balance Sheets — As of June 30, 2025 and December 31, 2024	10

	Condensed Consolidated Statements of Cash Flow — For the Six Months Ended June 30, 2025 and 2024	11

	Condensed Consolidated Statements of Equity — For the Three and Six Months Ended June 30, 2025 and 2024	12

	Notes to Condensed Consolidated Financial Statements	14

Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	50

Item 3.	Quantitative and Qualitative Disclosures About Market Risk	78

Item 4.	Controls and Procedures	80

PART II — OTHER INFORMATION

Item 1.	Legal Proceedings	80

Item 1A.	Risk Factors	81

Item 2.	Unregistered Sales of Equity Securities and Use of Proceeds	96

Item 5.	Other Information	96

Item 6.	Exhibits	97

Signatures		98

Table of Contents

NOTE REGARDING FORWARD-LOOKING STATEMENTS

This report contains forward-looking statements that are being made pursuant to the provisions of the Private Securities Litigation Reform Act of 1995 (the PSLRA) with the intention of obtaining the benefits of the “Safe Harbor” provisions of the PSLRA. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” "assume," “believe,” “contemplate,” “continue," "could," “estimate,” “expect,” “forecast,” “goal,” “guidance,” “hope,” “intend,” “may,” “objective,” "outlook," “plan,” “possible,” "potential," “predict,” “project,” “should,” “target,” “will,” “would” or the negative of these words or other words and terms of similar meaning. Given their forward-looking nature, these statements involve substantial risks and uncertainties and may be based on inaccurate assumptions. This report includes, among others, forward-looking statements regarding:

•our expected financial and operating performance;

•our long-term strategy and supporting business plans, including our product pipeline;

•our expectations about continued growth through acquisitions and key collaborative relationships and funding arrangements;

•our belief that our long-term competitive position depends upon our success in discovering and developing innovative, cost-effective products that serve unmet medical needs, along with our ability to manufacture products efficiently and to launch and market them effectively in a highly competitive environment;

•our ability to obtain and maintain adequate coverage, pricing and reimbursement from third-party payors;

•our expectations regarding certain legal and regulatory proceedings and investigations; and

•our belief that our existing funds, when combined with cash generated from operations and our access to additional financing resources, if needed, are sufficient to satisfy our operating, working capital, strategic alliance, milestone payment, capital expenditure and debt service requirements for the foreseeable future.

These forward-looking statements are based on management's current beliefs and assumptions and on information currently available to management. Given their nature, we cannot assure that any outcome expressed in these forward-looking statements will be realized in whole or in part. We caution that these statements are subject to risks and uncertainties, many of which are outside of our control and could cause future events or results to be materially different from those stated or implied in this document, including, among others, factors relating to:

•our substantial dependence on the anticipated amount, timing and accounting of revenue from our products, including from the successful development of new products and approval of additional indications for our existing products, including but not limited to LEQEMBI and SKYCLARYS;

•the anticipated amount, timing and accounting of contingent, milestone, royalty and other payments under licensing, collaboration, acquisition or divestiture agreements; tax positions and contingencies; collectability of receivables; pre-approval inventory; cost of sales; research and development costs; compensation and other selling, general and administrative expense; amortization of intangible assets; foreign currency exchange risk; estimated fair value of assets and liabilities; and impairment assessments, including for goodwill balances;

•expectations, plans, prospects and the timing of actions relating to product approvals, approvals of additional indications for our existing products, sales, pricing, growth, reimbursement and launch of our marketed and pipeline products all of which is subject to governmental and regulatory oversight, and therefore subject to risks, including but not limited to those related to approvals, unfavorable or delayed reimbursements and coverage determinations, and changes in reimbursement policies or practices of payors and other third parties;

•the potential impact of increased product competition in the biopharmaceutical and healthcare industry, as well as any other markets in which we compete, including increased competition from new originator therapies, generics, prodrugs and biosimilars of existing products and products approved under abbreviated regulatory pathways, including generic, prodrugs or biosimilar versions of our marketed products or competing products, including but not limited to, increased competition from TECFIDERA generic entrants in the U.S. and international markets and a biosimilar entrant of TYSABRI;

•patent terms, patent term extensions, patent office actions and expected availability and periods of regulatory exclusivity, as well as our ability to adequately enforce existing patents, including our European patent related to TECFIDERA;

•our ability to effectively implement our corporate strategy which includes significant investment in product and pipeline candidates, including but not limited to felzartamab, litifilimab and nusinersen;

Table of Contents

•the successful execution of our strategic and growth initiatives, including acquisitions, and our ability to realize the anticipated benefits from our acquisitions of Reata and HI-Bio, including future performance of the SKYCLARYS product and further development of the felzartamab product and anticipated synergies;

•the drivers for growing our business, including our plans and intention to commit resources relating to discovery, research and development programs and business development opportunities, including collaboration agreements, as well as the potential benefits and results of, and the anticipated completion of, certain business development transactions, reorganizations and cost-reduction measures, including our Fit for Growth program;

•the expectations, development plans and anticipated timelines, including costs and timing of potential clinical trials, regulatory filing approvals and/or discontinuation, of our products, drug candidates and pipeline programs, including collaborations with third parties including but not limited to Eisai and Sage, as well as the potential therapeutic scope of the development and commercialization of our and our collaborators’ pipeline products;

•the impacts of disruptions, turnover or changes in strategy, priorities or capabilities at our collaborators resulting from, for example, a change in control, and the related impacts on the commercialization or manufacturing of our shared products;

•the timing, outcome and impact of administrative, regulatory, legal and other proceedings, including those related to our patents and other proprietary and intellectual property rights, tax audits, assessments and settlements, pricing matters, sales and promotional practices, product liability, investigations and other matters;

•our ability to commercialize biosimilars, which is subject to risks such as our reliance on third parties, competitive challenges, regulatory compliance, adequate supply, intellectual property and regulatory challenges and failure to gain market and patient acceptance;

•our ability to finance our present and future operations and business initiatives and obtain funding for such activities on favorable terms;

•our ability to attract, retain and motivate qualified individuals for management and other employee positions in a highly competitive environment, including potential difficulty in retaining talent following acquisitions or following the discontinuation or underperformance of one or more marketed, pre-clinical or clinical programs;

•adverse safety events involving our marketed or pipeline products, generic, prodrugs or biosimilar versions of our marketed products or any other products from the same class as one of our products;

•the current and potential impacts of geopolitical tensions, acts of war and other large-scale crises, including impacts to our operations, sales and the possible disruptions or delay in our plans to conduct clinical trial activities in areas of geopolitical tension, including tensions between the U.S., China and other countries, regions affected by Russia's invasion of Ukraine and the military conflict in the Middle East;

•the direct and indirect impact of global health outbreaks or adverse weather events on our business and operations, including sales, expense, reserves and allowances, the supply chain, manufacturing, research and development costs, clinical trials and employees;

•our use of information technology systems and data and the potential impacts of any breakdowns, interruptions, invasions, corruptions, data breaches, destructions and/or other cybersecurity incidents of such systems or those of our business partners;

•our incorporation of technologies using AI into some of our processes;

•the potential impact of healthcare reform in the U.S., including the IRA (or other legislative acts that may modify or replace the IRA, such as the OBBBA) and the impact of the IRA Medicare Part D redesign, and measures being taken worldwide designed to reduce healthcare costs and limit the overall level of government expenditures, including the impact of pricing actions and reduced reimbursement for our products, as well as the potential impact of legislative and regulatory changes and priorities;

•our manufacturing capacity, including our ability to effectively manufacture biosimilars, reliance on third-party contract manufacturing organizations, plans and timing relating to changes in our manufacturing capabilities, our ability to adequately address global bulk supply risks, our ability to fully utilize our manufacturing facilities, including our Solothurn facility, activities in new or existing manufacturing facilities and the expected timeline

Table of Contents

for the gene therapy, clinical packaging and other manufacturing facility in RTP, North Carolina to be operational;

•the impact of the continued uncertainty of the credit and economic conditions in certain countries and our ability to collect accounts receivable in such countries;

•the impact of the increased volatility in the financial markets on our ability to obtain financing;

•lease commitments, purchase obligations and the timing and satisfaction of other contractual obligations;

•changes in our effective tax rate and obligations in various jurisdictions in which we are subject to taxation; and

•the impact of new laws, regulatory actions, judicial decisions, accounting standards and tariffs or trade restrictions, including any newly imposed U.S. tariffs and any responsive non-U.S. tariffs applicable to our products or operations, as well as the potential global macroeconomic effect of tariffs or trade restrictions.

These forward-looking statements involve risks and uncertainties, including those that are described in Part II, Item 1A. Risk Factors and Part I, Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations included in this report and elsewhere in this report, that could cause actual results to differ materially from those reflected in such statements. The factors identified above should not be construed as an exhaustive list of factors that could affect our future results and should be read in conjunction with the other cautionary statements that are included in our 2024 Form 10-K. Because some of these risks and uncertainties cannot be predicted or quantified and some are beyond our control, you should not rely on our forward-looking statements as predictions of future events and you should not place undue reliance on these statements. Moreover, we operate in a very competitive and rapidly changing environment, new risks and uncertainties may emerge from time to time and it is not possible for us to predict all risks nor identify all uncertainties. Forward-looking statements speak only as of the date of this report and are based on information and estimates available to us at this time. Except as required by law, we do not undertake any obligation to publicly update any forward-looking statements, whether as a result of new information, future developments or otherwise. You should read this report with the understanding that our actual future results, performance, events and circumstances might be materially different from what we expect.

NOTE REGARDING COMPANY AND PRODUCT REFERENCES

References in this report to:

•“Biogen,” the “company,” “we,” “us” and “our” refer to Biogen Inc. and its consolidated subsidiaries; and

•“RITUXAN” refers to both RITUXAN (the trade name for rituximab in the U.S., Canada and Japan) and MabThera (the trade name for rituximab outside the U.S., Canada and Japan).

NOTE REGARDING TRADEMARKS

ADUHELM®, AVONEX®, BYOOVIZ®, PLEGRIDY®, QALSODY®, RITUXAN®, RITUXAN HYCELA®, SKYCLARYS®, SPINRAZA®, TECFIDERA®, TYSABRI® and VUMERITY® are registered trademarks of Biogen.

BENEPALI™, FLIXABI™, FUMADERM™, IMRALDI™ and OPUVIZ™ are trademarks of Biogen.

ACTEMRA®, COLUMVI®, ENBREL®, EYLEA®, GAZYVA®, LEQEMBI®, HUMIRA®, LUCENTIS®, LUNSUMIO®, OCREVUS®, REMICADE®, ZURZUVAE™ and other trademarks referenced in this report are the property of their respective owners.

Table of Contents

DEFINED TERMS


2024 Form 10-K			Annual Report on Form 10-K for the year ended December 31, 2024
2020 Share Repurchase Program			Board of Directors authorized program to repurchase up to $5.0 billion of our common stock
2024 ESPP			Biogen Inc. 2024 Employee Stock Purchase Plan
2015 ESPP			Biogen Inc. 2015 Employee Stock Purchase Plan
2023 Term Loan			$1.5 billion term loan credit agreement
2025 Senior Notes			Senior Unsecured Notes Issued in May 2025
AbbVie			AbbVie Inc.
AI			Artificial Intelligence
ALS			Amyotrophic Lateral Sclerosis
AMR			Antibody-Mediated Rejection
AOCI			Accumulated Other Comprehensive Income (Loss)
ASO			Antisense Oligonucleotide
ASU			Accounting Standards Update
BLA			Biologics License Application
CCPA			California Consumer Privacy Act

CLE			Cutaneous Lupus Erythematosus
CLL			Chronic Lymphocytic Leukemia
CMS			Centers for Medicare & Medicaid Services
CODM			Chief Operating Decision Maker
Convergence			Convergence Pharmaceuticals Ltd.
CRL			Complete Response Letter
CROs			Contract Research Organizations
DEA			Drug Enforcement Agency
Denali			Denali Therapeutics Inc.
District Court			U.S. District Court for the District of Massachusetts
DOJ			U.S. Department of Justice
EC			European Commission
Eisai			Eisai Co., Ltd.
EMA			European Medicines Agency

E.U.			European Union
FA			Friedreich Ataxia
FASB			Financial Accounting Standards Board
FCPA			Foreign Corrupt Practices Act
FDA			U.S. Food and Drug Administration
Fit for Growth			Cost saving program initiated in 2023
G7			Group of Seven (comprised of Canada, France, Germany, Italy, Japan, the U.K. and the U.S.)
Genentech			Genentech, Inc.
GILTI			Global Intangible Low Tax Income
GloBE			Global Anti-Base Erosion
GMP			Good Manufacturing Practices
HI-Bio			Human Immunology Biosciences, Inc.
Humana			Humana Inc.
IgAN			Immunoglobulin A Nephropathy
IND			Investigational New Drug
IPR&D			In-process Research and Development
IRA			Inflation Reduction Act of 2022
IT			Information Technology

Table of Contents

DEFINED TERMS (continued)


IV			Intravenous
LEQEMBI Collaboration Agreement			Amended and Restated Collaboration Agreement entered into by Biogen MA Inc. and Eisai Co., Ltd. on October 22, 2017, as amended on March 13, 2022
LRRK2			Leucine-Rich Repeat Kinase 2
MAA			Marketing Authorization Application
MDD			Major Depressive Disorder
MorphoSys			MorphoSys AG
MS			Multiple Sclerosis
NDA			New Drug Application
Neurimmune			Neurimmune SubOne AG
OBBBA			One Big Beautiful Bill Act
OECD			Organization for Economic Co-operation and Development
ODD			Orphan Drug Designation
Organon			Organon LLC
PDUFA			Prescription Drug User Fee Act
PMN			Primary Membranous Nephropathy
PPACA			Patient Protection and Affordable Care Act
PPD			Postpartum Depression
PPMS			Primary Progressive MS
PRV			Priority Review Voucher
R&D			Research and Development
Reata			Reata Pharmaceuticals, Inc.
RMS			Relapsing MS
RNAi			RNA interference
RRMS			Relapsing-Remitting MS
RTP			Research Triangle Park
Sage			Sage Therapeutics, Inc.
Samsung Bioepis			Samsung Bioepis Co., Ltd.
Samsung BioLogics			Samsung BioLogics Co., Ltd.
Sangamo			Sangamo Therapeutics, Inc.
SEC			U.S. Securities and Exchange Commission
SG&A			Selling, General and Administrative
SLE			Systemic Lupus Erythematosus
SMA			Spinal Muscular Atrophy
SOD1			Superoxide Dismutase 1
SWISSMEDIC			Swiss Agency for Therapeutic Products
Transition Toll Tax			A one-time mandatory deemed repatriation tax on accumulated foreign subsidiaries' previously untaxed foreign earnings
U.K.			United Kingdom
U.S.			United States
U.S. GAAP			Accounting Principles Generally Accepted in the U.S.
VA			Veterans Affairs
VAT			Value-added Tax

Table of Contents

PART I FINANCIAL INFORMATION

BIOGEN INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(unaudited, in millions, except per share amounts)


	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2025		2024		2025		2024
Revenue:
Product revenue, net	$	1,878.7	$	1,899.6	$	3,605.2	$	3,611.5
Revenue from anti-CD20 therapeutic programs	467.3		444.5		845.5		838.5
Alzheimer's collaboration revenue	54.9		11.8		87.9		14.6
Contract manufacturing, royalty and other revenue	244.6		109.0		537.9		290.8
Total revenue	2,645.5		2,464.9		5,076.5		4,755.4
Cost and expense:
Cost of sales, excluding amortization and impairment of acquired intangible assets	605.0		546.0		1,234.3		1,088.2
Research and development	399.0		505.4		833.1		950.8
Acquired in-process research and development, upfront and milestone expense	46.6		8.5		247.3		16.0
Selling, general and administrative	583.8		553.8		1,156.3		1,135.3
Amortization and impairment of acquired intangible assets	130.9		86.9		242.7		165.2
Collaboration profit sharing/(loss reimbursement)	75.0		62.4		133.1		128.0
(Gain) loss on fair value remeasurement of contingent consideration	13.2		—		22.8		—

Restructuring charges	(0.7)		6.6		34.6		18.1
Gain on sale of priority review voucher, net	—		(88.6)		—		(88.6)
Other (income) expense, net	48.7		85.2		117.1		178.9
Total cost and expense	1,901.5		1,766.2		4,021.3		3,591.9
Income before income tax (benefit) expense	744.0		698.7		1,055.2		1,163.5
Income tax (benefit) expense	109.2		115.1		179.9		186.5



Net income attributable to Biogen Inc.	$	634.8	$	583.6	$	875.3	$	977.0

Net income per share:
Basic earnings per share attributable to Biogen Inc.	$	4.33	$	4.01	$	5.98	$	6.72
Diluted earnings per share attributable to Biogen Inc.	$	4.33	$	4.00	$	5.97	$	6.70

Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	146.5		145.6		146.3		145.4
Diluted earnings per share attributable to Biogen Inc.	146.7		145.9		146.7		145.9

See accompanying notes to these unaudited condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

(unaudited, in millions)


	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2025		2024		2025		2024
Net income attributable to Biogen Inc.	$	634.8	$	583.6	$	875.3	$	977.0
Other comprehensive income (loss):

Unrealized gains (losses) on cash flow hedges, net of tax	(105.8)		20.1		(163.6)		34.8

Unrealized gains (losses) on pension benefit obligation, net of tax	0.6		—		1.0		(0.1)
Currency translation adjustments, net of tax	41.6		(5.6)		60.7		(27.0)
Total other comprehensive income (loss), net of tax	(63.6)		14.5		(101.9)		7.7
Comprehensive income (loss) attributable to Biogen Inc.	$	571.2	$	598.1	$	773.4	$	984.7

See accompanying notes to these unaudited condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED BALANCE SHEETS

(unaudited, in millions, except per share amounts)


	As of June 30, 2025		As of December 31, 2024
ASSETS
Current assets:
Cash and cash equivalents	$	2,758.8	$	2,375.0

Accounts receivable, net of allowance for doubtful accounts of $2.9 and $2.2, respectively	1,624.2		1,404.8
Due from anti-CD20 therapeutic programs	459.8		464.0
Inventory	2,274.3		2,460.5
Other current assets	850.6		752.5
Total current assets	7,967.7		7,456.8

Property, plant and equipment, net	3,098.8		3,181.3
Operating lease assets	334.5		356.4
Intangible assets, net	9,467.5		9,691.2
Goodwill	6,493.1		6,478.9
Deferred tax asset	330.9		324.2
Investments and other assets	637.7		560.5
Total assets	$	28,330.2	$	28,049.3
LIABILITIES AND EQUITY
Current liabilities:
Current portion of notes payable	$	—	$	1,748.6
Taxes payable	114.8		548.3
Accounts payable	408.4		424.2
Accrued expense and other	2,660.5		2,807.7
Total current liabilities	3,183.7		5,528.8
Notes payable	6,283.7		4,547.2
Deferred tax liability	118.3		190.5
Long-term operating lease liabilities	310.9		334.5
Other long-term liabilities	799.6		732.3
Total liabilities	10,696.2		11,333.3
Commitments, contingencies and guarantees
Equity:
Biogen Inc. shareholders’ equity:
Preferred stock, par value $0.001 per share	—		—
Common stock, par value $0.0005 per share	0.1		0.1
Additional paid-in capital	714.0		569.4
Accumulated other comprehensive income (loss)	(238.1)		(136.2)
Retained earnings	20,135.1		19,259.8
Treasury stock, at cost	(2,977.1)		(2,977.1)


Total equity	17,634.0		16,716.0
Total liabilities and equity	$	28,330.2	$	28,049.3

See accompanying notes to these unaudited condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOW

(unaudited, in millions)


	For the Six Months Ended June 30,
	2025		2024
Cash flow from operating activities:
Net income	$	875.3	$	977.0
Adjustments to reconcile net income to net cash flow from operating activities:
Depreciation and amortization	377.5		306.4
Impairment of intangible assets	3.5		—
Excess and obsolescence charges related to inventory	14.3		44.4
Amortization of acquired inventory step-up	103.9		134.2

Share-based compensation	155.9		143.4
Contingent consideration	22.8		—
Deferred income taxes	(59.1)		(47.1)
(Gain) loss on strategic investments	33.2		61.6


Gain on sale of priority review voucher, net	—		(88.6)
Other	16.0		65.0
Changes in operating assets and liabilities, net of effects of business acquired:
Accounts receivable	(170.5)		12.3
Due from anti-CD20 therapeutic programs	4.2		(15.1)
Inventory	(27.9)		(188.2)
Accrued expense and other current liabilities	(318.7)		(115.6)
Income tax assets and liabilities	(534.7)		(7.7)
Other changes in operating assets and liabilities, net	(75.5)		(103.0)
Net cash flow provided by (used in) operating activities	420.2		1,179.0
Cash flow from investing activities:
Purchases of property, plant and equipment	(63.7)		(79.4)




Proceeds from sale of equity interest in Samsung Bioepis	—		406.8
Proceeds from sale of priority review voucher	—		103.0


Acquisitions of intangible assets	(10.0)		(84.1)
Proceeds from sales of strategic investments	—		57.5
Other	(30.6)		(3.3)
Net cash flow provided by (used in) investing activities	(104.3)		400.5
Cash flow from financing activities:

Payments related to issuance of stock for share-based compensation arrangements, net	(18.2)		(40.8)
Proceeds from borrowings	1,733.4		—
Repayments of borrowings	(1,750.0)		(650.0)

Other	0.1		6.0
Net cash flow provided by (used in) financing activities	(34.7)		(684.8)
Net increase (decrease) in cash and cash equivalents	281.2		894.7
Effect of exchange rate changes on cash and cash equivalents	102.6		(35.7)
Cash and cash equivalents, beginning of the period	2,375.0		1,049.9
Cash and cash equivalents, end of the period	$	2,758.8	$	1,908.9

See accompanying notes to these unaudited condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY

(unaudited, in millions)


	For the Three Months Ended June 30, 2025
	Preferred stock			Common stock			Additional paid-in capital		Accumulated other comprehensive income (loss)		Retained earnings		Treasury stock			Total equity
	Shares	Amount		Shares	Amount								Shares	Amount
Balance, March 31, 2025	—	$	—	170.3	$	0.1	$	629.9	$	(174.5)	$	19,500.3	(23.8)	$	(2,977.1)	$	16,978.7
Net income	—	—		—	—		—		—		634.8		—	—		634.8
Other comprehensive income (loss), net of tax	—	—		—	—		—		(63.6)		—		—	—		(63.6)




Issuance of common stock under stock option and stock purchase plans	—	—		0.1	—		6.9		—		—		—	—		6.9
Issuance of common stock under stock award plan	—	—		—	—		(0.8)		—		—		—	—		(0.8)
Compensation related to share-based payments	—	—		—	—		78.1		—		—		—	—		78.1
Other	—	—		—	—		(0.1)		—		—		—	—		(0.1)
Balance, June 30, 2025	—	$	—	170.4	$	0.1	$	714.0	$	(238.1)	$	20,135.1	(23.8)	$	(2,977.1)	$	17,634.0

	For the Six Months Ended June 30, 2025
	Preferred stock			Common stock			Additional paid-in capital		Accumulated other comprehensive income (loss)		Retained earnings		Treasury stock			Total equity
	Shares	Amount		Shares	Amount								Shares	Amount
Balance, December 31, 2024	—	$	—	169.5	$	0.1	$	569.4	$	(136.2)	$	19,259.8	(23.8)	$	(2,977.1)	$	16,716.0
Net income	—	—		—	—		—		—		875.3		—	—		875.3
Other comprehensive income (loss), net of tax	—	—		—	—		—		(101.9)		—		—	—		(101.9)




Issuance of common stock under stock option and stock purchase plans	—	—		0.3	—		22.1		—		—		—	—		22.1
Issuance of common stock under stock award plan	—	—		0.6	—		(40.3)		—		—		—	—		(40.3)
Compensation related to share-based payments	—	—		—	—		162.2		—		—		—	—		162.2
Other	—	—		—	—		0.6		—		—		—	—		0.6
Balance, June 30, 2025	—	$	—	170.4	$	0.1	$	714.0	$	(238.1)	$	20,135.1	(23.8)	$	(2,977.1)	$	17,634.0

See accompanying notes to these unaudited condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - (Continued)

(unaudited, in millions)


	For the Three Months Ended June 30, 2024
	Preferred stock			Common stock			Additional paid-in capital		Accumulated other comprehensive income (loss)		Retained earnings		Treasury stock			Total equity
	Shares	Amount		Shares	Amount								Shares	Amount
Balance, March 31, 2024	—	$	—	169.4	$	0.1	$	329.5	$	(160.5)	$	18,021.0	(23.8)	$	(2,977.1)	$	15,213.0
Net income	—	—		—	—		—		—		583.6		—	—		583.6
Other comprehensive income (loss), net of tax	—	—		—	—		—		14.5		—		—	—		14.5




Issuance of common stock under stock option and stock purchase plans	—	—		0.1	—		7.9		—		—		—	—		7.9
Issuance of common stock under stock award plan	—	—		—	—		(1.8)		—		—		—	—		(1.8)
Compensation related to share-based payments	—	—		—	—		72.9		—		—		—	—		72.9
Other	—	—		—	—		(1.0)		—		—		—	—		(1.0)
Balance, June 30, 2024	—	$	—	169.5	$	0.1	$	407.5	$	(146.0)	$	18,604.6	(23.8)	$	(2,977.1)	$	15,889.1

	For the Six Months Ended June 30, 2024
	Preferred stock			Common stock			Additional paid-in capital		Accumulated other comprehensive income (loss)		Retained earnings		Treasury stock			Total Biogen Inc. shareholders’ equity
	Shares	Amount		Shares	Amount								Shares	Amount
Balance, December 31, 2023	—	$	—	168.7	$	0.1	$	302.5	$	(153.7)	$	17,627.6	(23.8)	$	(2,977.1)	$	14,799.4
Net income	—	—		—	—		—		—		977.0		—	—		977.0
Other comprehensive income (loss), net of tax	—	—		—	—		—		7.7		—		—	—		7.7




Issuance of common stock under stock option and stock purchase plans	—	—		0.2	—		23.6		—		—		—	—		23.6
Issuance of common stock under stock award plan	—	—		0.6	—		(64.4)		—		—		—	—		(64.4)
Compensation related to share-based payments	—	—		—	—		149.0		—		—		—	—		149.0
Other	—	—		—	—		(3.2)		—		—		—	—		(3.2)
Balance, June 30, 2024	—	$	—	169.5	$	0.1	$	407.5	$	(146.0)	$	18,604.6	(23.8)	$	(2,977.1)	$	15,889.1

See accompanying notes to these unaudited condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited)


Note 1:			Summary of Significant Accounting Policies

References in these notes to "Biogen," the "company," "we," "us" and "our" refer to Biogen Inc. and its consolidated subsidiaries.

Business Overview

Biogen is a global biopharmaceutical company focused on discovering, developing and delivering innovative therapies for people living with serious and complex diseases. We have a broad portfolio of medicines to treat MS, have introduced the first approved treatment for SMA, co-developed treatments to address a defining pathology of Alzheimer’s disease and launched the first approved treatment to target a genetic cause of ALS. We market the first and only drug approved in the U.S., the E.U. and certain international markets for the treatment of FA in adults and adolescents aged 16 years and older. We are focused on advancing our pipeline in neurology, specialized immunology and rare diseases. We support our drug discovery and development efforts through internal research and development programs, external collaborations and acquisitions.

Our marketed products include TECFIDERA, VUMERITY, AVONEX, PLEGRIDY and TYSABRI for the treatment of MS; SPINRAZA for the treatment of SMA; SKYCLARYS for the treatment of FA; and QALSODY for the treatment of ALS.

We also have collaborations with Eisai on the commercialization of LEQEMBI for the treatment of Alzheimer's disease and Sage on the commercialization of ZURZUVAE for the treatment of PPD. We have certain business and financial rights with respect to RITUXAN for the treatment of non-Hodgkin's lymphoma, CLL and other conditions; RITUXAN HYCELA for the treatment of non-Hodgkin's lymphoma and CLL; GAZYVA for the treatment of CLL and follicular lymphoma; OCREVUS for the treatment of PPMS and RMS; LUNSUMIO for the treatment of relapsed or refractory follicular lymphoma; COLUMVI, a bispecific antibody for the treatment of non-Hodgkin's lymphoma; and have the option to add other potential anti-CD20 therapies, pursuant to our collaboration arrangements with Genentech, a wholly-owned member of the Roche Group.

We commercialize a portfolio of biosimilars of advanced biologics including: BENEPALI, an etanercept biosimilar referencing ENBREL; IMRALDI, an adalimumab biosimilar referencing HUMIRA; FLIXABI, an infliximab biosimilar referencing REMICADE; and BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS, in certain international markets. We also have commercialization rights related to OPUVIZ, an aflibercept biosimilar referencing EYLEA, in certain international markets.

For additional information on our collaboration arrangements, please read Note 19, Collaborative and Other Relationships, to these unaudited condensed consolidated financial statements (condensed consolidated financial statements).

Basis of Presentation

In the opinion of management, our condensed consolidated financial statements include all adjustments, consisting of normal recurring accruals, necessary for a fair statement of our financial statements for interim periods in accordance with U.S. GAAP. The information included in this quarterly report on Form 10-Q should be read in conjunction with our audited consolidated financial statements and the accompanying notes included in our 2024 Form 10-K. Our accounting policies are described in the Notes to Consolidated Financial Statements in our 2024 Form 10-K and updated, as necessary, in this report. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from our audited financial statements, but does not include all disclosures required by U.S. GAAP. The results of operations for the three and six months ended June 30, 2025, are not necessarily indicative of the operating results for the full year or for any other subsequent interim period.

We operate as one operating segment, focused on discovering, developing and delivering innovative therapies for people living with serious and complex diseases.

During the first quarter of 2025 we began presenting acquired in-process research and development, upfront and milestone expense as a separate line item in our condensed consolidated statements of income. Acquired in-process research and development, upfront and milestone expense includes costs incurred in connection with collaboration and license agreements such as upfront and milestone payments and, when applicable, premiums on equity securities and asset acquisitions of acquired in-process research and development, which were previously included in research and development expense. Prior periods have been reclassified to conform to the current period

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

presentation. The reclassification had no impact on our total cost and expense, net income attributable to Biogen Inc., earnings per share or total equity.

Consolidation

Our condensed consolidated financial statements reflect our financial statements, those of our wholly-owned subsidiaries and variable interest entities where we are the primary beneficiary. For consolidated entities where we own or are exposed to less than 100.0% of the economics, we record net income (loss) attributable to noncontrolling interests, net of tax in our condensed consolidated statements of income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. Intercompany balances and transactions are eliminated in consolidation.

In determining whether we are the primary beneficiary of a variable interest entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. We continuously assess whether we are the primary beneficiary of a variable interest entity as changes to existing relationships or future transactions may result in us consolidating or deconsolidating one or more of our collaborators or partners.

Use of Estimates

The preparation of our condensed consolidated financial statements requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, equity, revenue and expense and related disclosure of contingent assets and liabilities. On an ongoing basis we evaluate our estimates, judgments and assumptions. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets, liabilities and equity and the amount of revenue and expense. Actual results may differ from these estimates.

Significant Accounting Policies

There have been no material changes to our significant accounting policies disclosed in Note 1, Summary of Significant Accounting Policies, to our audited consolidated financial statements included in our 2024 Form 10-K.

New Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that we adopt as of the specified effective date. Unless otherwise discussed below, we do not believe that the adoption of recently issued standards have had, or may have, a material impact on our condensed consolidated financial statements or disclosures.

Standard

Description

Effective Date

Effects on the financial statements

ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures

This standard establishes incremental disaggregation of income tax disclosures pertaining to the effective tax rate reconciliation and income taxes paid. The amendments in this update are required to be applied on a prospective basis with the option to apply it retrospectively.

Annual reporting for fiscal years beginning after December 15, 2024. Early adoption is permitted.

We are currently evaluating the potential impact that this new standard will have on our consolidated financial statements and related disclosures, and expect to apply this standard prospectively upon adoption.

ASU No. 2024-03, Income Statement (Subtopic 220-40): Reporting Comprehensive Income - Expense Disaggregation Disclosures

This standard requires disclosure in the notes to the financial statements, at each interim and annual reporting period, of specified information about certain costs and expense including purchases of inventory, employee compensation, depreciation and intangible asset amortization included in each relevant expense caption. This standard also requires a qualitative description of the amounts remaining in relevant expense captions that are not separately disaggregated, as well as disclosure of the total amount of selling expenses, and, in annual reporting periods, an entity’s definition of selling expenses.

Annual reporting for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted.

We are currently evaluating the potential impact that this new standard will have on our consolidated financial statements and related disclosures.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


Note 2:			Acquisitions

Human Immunology Biosciences

On July 2, 2024, we completed the acquisition of all of the issued and outstanding shares of HI-Bio, a privately-held clinical-stage biotechnology company focused on targeted therapies for patients with severe immune-mediated diseases. HI-Bio's lead asset, felzartamab, an anti-CD38 antibody, is currently being evaluated for three leading indications, AMR, PMN and IgAN. Felzartamab has received Breakthrough Therapy Designation and ODD from the FDA for development in the treatment of PMN and AMR. Subsequent to our acquisition, felzartamab received ODD in the E.U. in IgAN and solid organ transplantation. The acquisition of HI-Bio is expected to augment our pipeline and build on our expertise in immunology.

Under the terms of this acquisition, we paid shareholders of HI-Bio approximately $1.15 billion at closing and may pay up to an additional $650.0 million in contingent development and regulatory milestone payments. The $1.15 billion paid includes approximately $74.5 million related to HI-Bio's outstanding, non-vested equity awards, inclusive of employer taxes, of which $56.4 million was recognized as share-based compensation payments to settle non-vested equity awards attributable to the post-acquisition service period and therefore not reflected as a component of total purchase price paid. Of the total $56.4 million, we recognized approximately $42.5 million as a charge to research and development expense with the remaining $13.9 million as a charge to selling, general and administrative expense within our consolidated statements of income for the year ended December 31, 2024, included in our 2024 Form 10-K. These amounts were associated with the accelerated vesting of stock options and RSUs previously granted to HI-Bio employees and required no future services to vest.

Upon closing we also paid an additional $43.7 million related to working capital adjustments as of the transaction close date, which was included as a component of total purchase price paid.

We funded this acquisition through available cash on hand and accounted for this acquisition as a business combination using the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations, and recorded assets acquired and liabilities assumed at their respective fair values as of the acquisition date.

Purchase Price Consideration

Total consideration transferred for the acquisition of HI-Bio is summarized as follows:


(In millions)	As of July 2, 2024
Cash consideration paid to HI-Bio shareholders(1)	$	1,137.3
Contingent consideration	485.1

Total consideration	$	1,622.4

(1) Represents total consideration paid to shareholders of HI-Bio of $1.15 billion, plus an additional $43.7 million related to working capital adjustments as of the transaction close date, less $56.4 million of cash paid for HI-Bio's outstanding, non-vested equity awards, inclusive of employer taxes, which were recognized as compensation attributable to the post-acquisition service period and therefore not reflected as a component of total consideration.

Contingent Consideration: We may make certain contingent payments to the former shareholders of HI-Bio upon the achievement of certain development and regulatory milestones. As of the acquisition date, the maximum aggregate amount payable for these potential milestones was $650.0 million. The acquisition-date fair value of these milestones was approximately $485.1 million and was estimated utilizing a probability-adjusted discounted cash flow calculation using an appropriate discount rate dependent on the nature and timing of the milestone payments, which ranged from 6.2% to 7.0%, and probabilities of technological and regulatory success ranging from 67.0% to near-certain probability. Of the total contingent consideration, approximately $279.3 million related to milestones classified as short-term and reflected as a component of accrued expense and other with the remaining $205.8 million reflected as a component of other long-term liabilities within our condensed consolidated balance sheets. The short-term liability related to the fourth patient dosed in a Phase 3 clinical trial of felzartamab in a first and second indication, which would each result in the achievement of a $150.0 million milestone payment. During the second quarter of 2025 the first milestone related to the fourth patient dosed in a phase 3 clinical trial of felzartamab for AMR was achieved, resulting in a $150.0 million milestone payment made to the former shareholders of HI-Bio, which was substantially paid in July 2025.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Subsequent changes in the fair value of the contingent consideration obligation are being recognized as (gain) loss on fair value remeasurement of contingent consideration within our condensed consolidated statements of income. This fair value measurement is based on significant inputs that are not observable in the market and thus represent Level 3 fair value measurements. For additional information related to the fair value of this obligation, please read Note 8, Fair Value Measurements, to these condensed consolidated financial statements.

Other Contractual Commitments: We acquired HI-Bio's pre-existing in-license commitments under third-party agreements with MorphoSys, which included tiered royalties on potential future sales ranging from high-single digit to mid-teen percentages, as well as potential development, regulatory and commercial milestone payments of up to $130.0 million, $230.0 million and $640.0 million, respectively. At the transaction close date the achievement of these milestones was not considered probable and therefore not recorded in our financial statements.

Purchase Price Allocation

We finalized purchase accounting for this acquisition in the second quarter of 2025.

The following table summarizes the amounts recognized for assets acquired and liabilities assumed as of the acquisition date, and reflects measurement period adjustments made to the amounts initially recorded as of the acquisition date on July 2, 2024. The related impact to our condensed consolidated statements of income that would have been recognized in previous periods if the adjustments were recognized as of the acquisition date is immaterial.


(In millions)	Amounts Recognized as of Acquisition Date (as adjusted) June 30, 2025
Cash and cash equivalents	$	62.5

Intangible assets:
IPR&D - felzartamab (IgAN)	920.0
IPR&D - felzartamab (AMR)	450.0
IPR&D - felzartamab (PMN)	265.0
Other clinical programs	7.9
Prepaid expense and other assets(1)	1.4

Operating lease assets	1.2
Accounts payable	(1.1)
Accrued liabilities	(35.0)
Deferred tax liability(1)	(309.3)
Operating lease liabilities	(1.2)

Total identifiable net assets	1,361.4
Goodwill(1)	261.0
Total assets acquired and liabilities assumed	$	1,622.4

(1) Includes measurement period adjustments recorded in 2025 that increased prepaid expense and other assets by $0.4 million, net deferred tax liability by $4.9 million and goodwill by $4.5 million.

Intangible assets: Intangible assets comprised of approximately $1.6 billion of IPR&D related to HI-Bio's lead asset felzartamab. This includes $920.0 million of IPR&D related to felzartamab indication for IgAN, $450.0 million of IPR&D related to felzartamab indication for AMR and $265.0 million of IPR&D related to felzartamab indication for PMN. The estimated fair values of the program related intangible assets were determined using a multi-period excess earnings method, a form of the income approach, utilizing cash flow analyses and a discount rate of 14.5%. These fair value measurements were based on significant inputs that are not observable in the market and thus represent Level 3 fair value measurements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Goodwill: Goodwill was calculated as the excess of the consideration transferred over the net assets recognized and represents the future economic benefits arising from the other assets acquired that could not be individually identified and separately recognized. We recognized goodwill of approximately $261.0 million, which includes measurement period adjustments, and is not deductible for tax purposes. The goodwill recognized from our acquisition of HI-Bio is primarily the result of the deferred tax consequences from the transaction recorded for financial statement purposes.

Acquisition-related expense: Acquisition-related expense, primarily comprised of advisory and legal fees, and other transaction costs, totaled approximately $2.8 million and were recorded within selling, general and administrative expense within our consolidated statements of income for the year ended December 31, 2024, included in our 2024 Form 10-K.


Note 3:			Dispositions

Sale of Joint Venture Equity Interest in Samsung Bioepis

In April 2022 we completed the sale of our 49.9% equity interest in Samsung Bioepis to Samsung BioLogics in exchange for total consideration of approximately $2.3 billion. Under the terms of this transaction, we received approximately $1.0 billion in cash at closing, with approximately $1.3 billion in cash to be deferred over two payments. The first deferred payment of $812.5 million was received in April 2023 and the second deferred payment of $437.5 million was received in April 2024.

For the three and six months ended June 30, 2024, we recognized gains of approximately $1.4 million and $7.5 million, respectively, to reflect the changes in fair value associated with the passage of time related to the second deferred payment due to us, which was received in April 2024 and recorded in other (income) expense, net within our condensed consolidated statements of income.

For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 3, Dispositions, to our consolidated financial statements included in our 2024 Form 10-K.

Sale of Priority Review Voucher

In April 2024 we completed the sale of our rare pediatric disease PRV, generated by the development associated with SPINRAZA, to a third party. In consideration for the PRV we received a cash payment of $103.0 million upon the closing of the PRV purchase, of which approximately $14.4 million was paid to Ionis. Our net portion of approximately $88.6 million was recognized in gain on sale of priority review voucher, net within our condensed consolidated statements of income for the three and six months ended June 30, 2024.

Sale of TOFIDENCE

In March 2025 we completed the sale of our regulatory and commercial rights in the U.S. for TOFIDENCE, a tocilizumab biosimilar referencing ACTEMRA, to Organon. Under the terms of this transaction, we received a payment of approximately $51.0 million in July 2025 and recognized a de minimis loss within our condensed consolidated statements of income for the six months ended June 30, 2025.


Note 4:			Restructuring

2023 Fit for Growth Restructuring Program

In 2023 we initiated cost saving measures as part of our Fit for Growth program to reduce operating costs, while improving operating efficiency and effectiveness. The Fit for Growth program is expected to generate approximately $1.0 billion in gross operating expense savings by the end of 2025, some of which will be reinvested in various initiatives. The Fit for Growth program is currently estimated to include net headcount reductions of approximately 1,400 employees and we expect to incur total restructuring charges ranging from approximately $300.0 million to $310.0 million. As of June 30, 2025, cumulative total restructuring charges incurred in connection with our Fit for Growth program totaled approximately $300.0 million.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Total charges incurred from our 2023 Fit for Growth program are summarized as follows:


	For the Three Months Ended June 30,
	2025						2024
(In millions)	Severance Costs		Accelerated Depreciation and Other Costs		Total		Severance Costs		Accumulated Depreciation and Other Costs		Total
Selling, general and administrative	$	—	$	0.7	$	0.7	$	—	$	2.0	$	2.0
Research and development	—		1.3		1.3		—		2.2		2.2
Restructuring charges	(1.1)		—		(1.1)		6.3		—		6.3
Total charges	$	(1.1)	$	2.0	$	0.9	$	6.3	$	4.2	$	10.5

	For the Six Months Ended June 30,
	2025						2024
(In millions)	Severance Costs		Accelerated Depreciation and Other Costs		Total		Severance Costs		Accumulated Depreciation and Other Costs		Total
Selling, general and administrative	$	—	$	(3.2)	$	(3.2)	$	—	$	3.4	$	3.4
Research and development	—		6.4		6.4		—		7.1		7.1
Restructuring charges	34.2		—		34.2		15.6		—		15.6
Total charges	$	34.2	$	3.2	$	37.4	$	15.6	$	10.5	$	26.1

Other Costs: Includes costs associated with items such as asset abandonment and write-offs, facility closure costs, pre-tax gains and losses resulting from the termination of certain leases, employee non-severance expense, consulting fees and other costs.

Reata Integration

Following the close of our Reata acquisition in September 2023, we implemented an integration plan designed to realize operating synergies through cost savings and avoidance. Under this initiative, we estimate we will incur total integration charges of approximately $35.0 million related to severance and employment costs. These severance and employment costs were substantially incurred during 2023.

Total charges incurred from our Reata integration are summarized as follows:


	For the Three Months Ended June 30,
	2025						2024
(In millions)	Severance Costs		Accelerated Depreciation and Other Costs		Total		Severance Costs		Accumulated Depreciation and Other Costs		Total
Selling, general and administrative	$	—	$	1.8	$	1.8	$	—	$	1.5	$	1.5
Research and development	—		4.0		4.0		—		3.3		3.3
Restructuring charges	—		—		—		0.3		—		0.3
Total charges	$	—	$	5.8	$	5.8	$	0.3	$	4.8	$	5.1

	For the Six Months Ended June 30,
	2025						2024
(In millions)	Severance Costs		Accelerated Depreciation and Other Costs		Total		Severance Costs		Accumulated Depreciation and Other Costs		Total
Selling, general and administrative	$	—	$	3.6	$	3.6	$	—	$	3.3	$	3.3
Research and development	—		6.3		6.3		—		6.0		6.0
Restructuring charges	(0.2)		—		(0.2)		2.5		—		2.5
Total charges	$	(0.2)	$	9.9	$	9.7	$	2.5	$	9.3	$	11.8

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

In connection with our acquisition of Reata we assumed responsibility for a single-tenant, build-to-suit building of approximately 327,400 square feet of office and laboratory space located in Plano, Texas, with an initial lease term of 16 years. We do not intend to occupy this building and are evaluating opportunities to sublease the property. For additional information on our acquisition of Reata, please read Note 2, Acquisitions, to our consolidated financial statements included in our 2024 Form 10-K.

Restructuring Reserve

Charges and spending related to workforce reductions are summarized as follows:


	Workforce Reductions
(In millions)	2025		2024

Restructuring reserve as of January 1	$	31.9		$	75.4
Expense	35.3			11.5
Payment	(25.8)			(42.2)
Foreign currency and other adjustments	(1.0)			0.8
Restructuring reserve as of March 31	40.4			45.5
Expense	(0.7)			6.6
Payment	(9.5)			(11.9)
Foreign currency and other adjustments	(1.0)			—
Restructuring reserve as of June 30	$	29.2		$	40.2

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


Note 5:			Revenue

Product Revenue

Revenue by product is summarized as follows:


	For the Three Months Ended June 30,
	2025						2024
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis:
TECFIDERA	$	47.2	$	146.4	$	193.6	$	44.1	$	208.1	$	252.2
VUMERITY	188.0		24.3		212.3		144.2		21.6		165.8
Total Fumarate	235.2		170.7		405.9		188.3		229.7		418.0
AVONEX	121.7		56.0		177.7		117.2		65.6		182.8
PLEGRIDY	28.3		40.7		69.0		28.2		39.9		68.1
Total Interferon	150.0		96.7		246.7		145.4		105.5		250.9
TYSABRI	272.2		182.4		454.6		248.7		213.5		462.2
FAMPYRA(1)	—		—		—		—		18.7		18.7
Subtotal: Multiple Sclerosis	657.4		449.8		1,107.2		582.4		567.4		1,149.8

Rare Disease:
SPINRAZA	149.3		243.4		392.7		157.3		271.8		429.1
SKYCLARYS(2)	78.0		52.3		130.3		75.6		24.4		100.0
QALSODY(3)	7.5		12.5		20.0		4.6		0.4		5.0
Subtotal: Rare Disease	234.8		308.2		543.0		237.5		296.6		534.1

Biosimilars:
BENEPALI	—		112.1		112.1		—		117.3		117.3
IMRALDI	—		46.7		46.7		—		53.2		53.2
FLIXABI	—		14.3		14.3		—		13.1		13.1
BYOOVIZ	2.5		6.1		8.6		10.3		3.4		13.7
TOFIDENCE	—		—		—		0.8		—		0.8
Subtotal: Biosimilars	2.5		179.2		181.7		11.1		187.0		198.1

Other:
ZURZUVAE	46.4		—		46.4		14.9		—		14.9


Other(4)	—		0.4		0.4		0.8		1.9		2.7
Subtotal: Other	46.4		0.4		46.8		15.7		1.9		17.6
Total product revenue, net	$	941.1	$	937.6	$	1,878.7	$	846.7	$	1,052.9	$	1,899.6

(1) Effective January 1, 2025, our collaboration and license agreement for FAMPYRA global commercialization rights was terminated.

(2) SKYCLARYS became commercially available in the E.U. during the first quarter of 2024.

(3) QALSODY became commercially available in the E.U. during the second quarter of 2024.

(4) Other includes FUMADERM and ADUHELM.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


	For the Six Months Ended June 30,
	2025						2024
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis:
TECFIDERA	$	87.0	$	312.7	$	399.7	$	87.8	$	418.7	$	506.5
VUMERITY	305.1		46.0		351.1		250.1		43.2		293.3
Total Fumarate	392.1		358.7		750.8		337.9		461.9		799.8
AVONEX	230.3		114.2		344.5		228.4		132.9		361.3
PLEGRIDY	52.4		76.1		128.5		56.8		76.4		133.2
Total Interferon	282.7		190.3		473.0		285.2		209.3		494.5
TYSABRI	473.0		363.1		836.1		462.5		431.0		893.5
FAMPYRA(1)	—		0.3		0.3		—		37.9		37.9
Subtotal: Multiple Sclerosis	1,147.8		912.4		2,060.2		1,085.6		1,140.1		2,225.7

Rare Disease:
SPINRAZA	303.7		512.9		816.6		305.8		464.6		770.4
SKYCLARYS(2)	147.1		107.1		254.2		148.6		29.4		178.0
QALSODY(3)	15.0		20.5		35.5		9.0		0.6		9.6
Subtotal: Rare Disease	465.8		640.5		1,106.3		463.4		494.6		958.0

Biosimilars:
BENEPALI	—		223.4		223.4		—		236.0		236.0
IMRALDI	—		94.1		94.1		—		108.0		108.0
FLIXABI	—		27.4		27.4		—		30.9		30.9
BYOOVIZ	6.7		10.8		17.5		14.0		5.3		19.3
TOFIDENCE	0.1		—		0.1		0.8		—		0.8
Subtotal: Biosimilars	6.8		355.7		362.5		14.8		380.2		395.0

Other:
ZURZUVAE	74.1		—		74.1		27.3		—		27.3


Other(4)	0.4		1.7		2.1		1.7		3.8		5.5
Subtotal: Other	74.5		1.7		76.2		29.0		3.8		32.8
Total product revenue, net	$	1,694.9	$	1,910.3	$	3,605.2	$	1,592.8	$	2,018.7	$	3,611.5

(1) Effective January 1, 2025, our collaboration and license agreement for FAMPYRA global commercialization rights was terminated.

(2) SKYCLARYS became commercially available in the E.U. during the first quarter of 2024.

(3) QALSODY became commercially available in the E.U. during the second quarter of 2024.

(4) Other includes FUMADERM and ADUHELM.

We recognized revenue from two wholesalers accounting for 28.2% and 15.8% of gross product revenue for the three months ended June 30, 2025, and 27.1% and 15.0% of gross product revenue for the six months ended June 30, 2025.

We recognized revenue from two wholesalers accounting for 25.4% and 12.3% of gross product revenue for the three months ended June 30, 2024, and 25.5% and 12.0% of gross product revenue for the six months ended June 30, 2024.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

An analysis of the change in reserves for discounts and allowances is summarized as follows:


(In millions)	Discounts		Contractual Adjustments		Returns		Total
Balance, December 31, 2024	$	162.7	$	880.8	$	48.1	$	1,091.6
Current provisions relating to sales in current year	394.1		1,402.1		14.9		1,811.1
Adjustments relating to prior years	1.4		(63.7)		3.3		(59.0)
Payments/credits relating to sales in current year	(290.4)		(744.1)		(0.2)		(1,034.7)
Payments/credits relating to sales in prior years	(91.8)		(440.4)		(5.8)		(538.0)
Balance, June 30, 2025	$	176.0	$	1,034.7	$	60.3	$	1,271.0

The total reserves above, which are included in our condensed consolidated balance sheets, are summarized as follows:


(In millions)	As of June 30, 2025		As of December 31, 2024
Reduction of accounts receivable	$	273.6	$	154.1
Component of accrued expense and other	997.4		937.5
Total revenue-related reserves	$	1,271.0	$	1,091.6

Revenue from Anti-CD20 Therapeutic Programs

Revenue from anti-CD20 therapeutic programs is summarized in the table below. For the purposes of this footnote, we refer to RITUXAN and RITUXAN HYCELA collectively as RITUXAN.


	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2025		2024		2025		2024
Royalty revenue on sales of OCREVUS	$	353.8	$	336.3	$	642.6	$	639.0
Biogen’s share of pre-tax profits in the U.S. for RITUXAN, GAZYVA and LUNSUMIO	107.7		103.4		191.4		190.5
Other revenue from anti-CD20 therapeutic programs	5.8		4.8		11.5		9.0
Total revenue from anti-CD20 therapeutic programs	$	467.3	$	444.5	$	845.5	$	838.5

For additional information on our collaboration arrangements with Genentech, please read Note 19, Collaborative and Other Relationships, to these condensed consolidated financial statements.

Alzheimer's Collaboration Revenue

Alzheimer's collaboration revenue consists of our 50.0% share of LEQEMBI product revenue, net and cost of sales, including royalties, as we are not the principal. We began recognizing Alzheimer's collaboration revenue upon the accelerated approval of LEQEMBI in the U.S. during the first quarter of 2023.

For the three and six months ended June 30, 2025, we recognized Alzheimer's collaboration revenue of approximately $54.9 million and $87.9 million, respectively, compared to $11.8 million and $14.6 million, respectively, in the prior year comparative periods.

For additional information on our collaboration arrangements with Eisai, please read Note 19, Collaborative and Other Relationships, to these condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Contract Manufacturing, Royalty and Other Revenue

Contract manufacturing, royalty and other revenue is summarized as follows:


	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2025		2024		2025		2024
Contract manufacturing revenue	$	225.0	$	100.0	$	507.3	$	252.2
Royalty and other revenue	19.6		9.0		30.6		38.6
Total contract manufacturing, royalty and other revenue	$	244.6	$	109.0	$	537.9	$	290.8

Contract Manufacturing Revenue

Contract manufacturing revenue primarily reflects amounts earned under contract manufacturing agreements with our strategic customers and batches of LEQEMBI related to our collaboration with Eisai.

Royalty and Other Revenue

Royalty and other revenue primarily reflects royalty revenue on biosimilar products from our license arrangements with Samsung Bioepis and royalties we receive from net sales on products related to patents that we have out-licensed.

For additional information on our license arrangements with Samsung Bioepis and our collaboration arrangements with Eisai, please read Note 19, Collaborative and Other Relationships, to these condensed consolidated financial statements.


Note 6:			Inventory

The components of inventory are summarized as follows:


(In millions)	As of June 30, 2025		As of December 31, 2024
Raw materials	$	305.0	$	317.8
Work in process	1,641.9		1,882.8
Finished goods	478.0		353.8
Total inventory	$	2,424.9	$	2,554.4

Balance Sheet Classification:
Inventory	$	2,274.3	$	2,460.5
Investments and other assets	150.6		93.9
Total inventory	$	2,424.9	$	2,554.4

Long-term inventory is included in investments and other assets within our condensed consolidated balance sheets.

As a result of our acquisition of Reata in September 2023 we recorded a fair value step-up adjustment related to the acquired inventory of SKYCLARYS of approximately $1.3 billion. This fair value step-up adjustment is being amortized to cost of sales within our condensed consolidated statements of income as the inventory is sold or used for clinical purposes. We expect this amount to be fully amortized by the end of 2028. For the three and six months ended June 30, 2025, amortization from the fair value step-up adjustment was approximately $52.5 million and $103.9 million, respectively. For the three and six months ended June 30, 2024, amortization from the fair value step-up adjustment was approximately $90.1 million and $134.2 million, respectively, which includes approximately $46.0 million of inventory used for clinical purposes, which is reflected in research and development expense within our condensed consolidated statements of income. For additional information on our acquisition of Reata, please read Note 2, Acquisitions, to our consolidated financial statements included in our 2024 Form 10-K.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


Note 7:			Intangible Assets and Goodwill

Intangible Assets

Intangible assets, net of accumulated amortization, impairment charges and adjustments are summarized as follows:


		As of June 30, 2025						As of December 31, 2024
(In millions)	Estimated Life	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net



Completed technology	2-31 years	$	14,087.1	$	(6,423.0)	$	7,664.1	$	14,138.4	$	(6,254.1)	$	7,884.3
In-process research and development	Indefinite until commercialization	1,639.4		—		1,639.4		1,642.9		—		1,642.9
Priority review voucher	Indefinite	100.0		—		100.0		100.0		—		100.0
Trademarks and trade names	Indefinite	64.0		—		64.0		64.0		—		64.0
Total intangible assets		$	15,890.5	$	(6,423.0)	$	9,467.5	$	15,945.3	$	(6,254.1)	$	9,691.2

Amortization and Impairments

For the three and six months ended June 30, 2025, amortization and impairment of acquired intangible assets totaled $130.9 million and $242.7 million, respectively, compared to $86.9 million and $165.2 million, respectively, in the prior year comparative periods.

For the three and six months ended June 30, 2025, amortization of acquired intangible assets, excluding impairment charges, totaled $127.4 million and $239.2 million, respectively, compared to $86.9 million and $165.2 million, respectively, in the prior year comparative periods. The increases were primarily due to amortization for the acquired intangible assets associated with SKYCLARYS and TYSABRI.

For the three and six months ended June 30, 2025, amortization and impairment of acquired intangible assets reflects the impact of a $3.5 million impairment charge related to a compound acquired from HI-Bio. For the three and six months ended June 30, 2024, we had no impairment charges.

Completed Technology

Completed technology primarily relates to our other marketed products and programs acquired through asset acquisitions, licenses and business combinations. Completed technology intangible assets are amortized over their estimated useful lives, which range between 2 to 31 years, with a remaining weighted average useful life of 12 years.

IPR&D Related to Business Combinations

IPR&D represents the fair value assigned to research and development assets that we acquired as part of a business combination and had not yet reached technological feasibility at the date of acquisition. Included in IPR&D balances are adjustments related to foreign currency exchange rate fluctuations.

The carrying value associated with our IPR&D assets as of June 30, 2025 and December 31, 2024, primarily relates to the IPR&D programs we acquired in connection with our acquisition of HI-Bio in July 2024, with an estimated fair value of approximately $1.6 billion.

Priority Review Voucher

In connection with our acquisition of Reata in September 2023 we acquired a rare pediatric disease PRV which may be used to obtain priority review by the FDA for a future regulatory submission or sold to a third party. We recorded the PRV based on its estimated fair value of $100.0 million as an intangible asset.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Estimated Future Amortization of Intangible Assets

The estimated future amortization of finite-lived intangible assets for the next five years is expected to be as follows:


(In millions)	As of June 30, 2025
2025 (remaining six months)	$	240.0
2026	565.0
2027	600.0
2028	630.0
2029	665.0
2030	700.0

Goodwill

The following table provides a roll forward of the changes in our goodwill balance:


(In millions)	As of June 30, 2025
Goodwill, December 31, 2024	$	6,478.9
Goodwill resulting from HI-Bio acquisition(1)	4.5

Other(2)	9.7
Goodwill, June 30, 2025	$	6,493.1

(1) Goodwill resulting from the HI-Bio acquisition relates to HI-Bio measurement period adjustments recognized during 2025 related to certain income tax adjustments. For additional information on our acquisition of HI-Bio, please read Note 2, Acquisitions, to these condensed consolidated financial statements.

(2) Other includes adjustments related to foreign currency exchange rate fluctuations.

As of June 30, 2025, we had no impairment losses related to goodwill.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


Note 8:			Fair Value Measurements

The tables below present information about our assets and liabilities that are regularly measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques we utilized to determine such fair value:


	Fair Value Measurements on a Recurring Basis
	As of June 30, 2025
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,234.9	$	—	$	2,234.9	$	—




Marketable equity securities	157.0		157.0		—		—
Other current assets:

Derivative contracts	31.7		—		31.7		—
Other non-current assets:
Convertible note(1)	30.0		—		—		30.0
Plan assets for deferred compensation	50.1		—		50.1		—

Total	$	2,503.7	$	157.0	$	2,316.7	$	30.0
Liabilities:
Other current liabilities:
Derivative contracts	$	123.7	$	—	$	123.7	$	—
Contingent consideration obligations	297.2		—		—		297.2
Other non-current liabilities:
Derivative contracts	26.8		—		26.8		—
Contingent consideration obligations	237.7		—		—		237.7
Total	$	685.4	$	—	$	150.5	$	534.9

(1) As part of our strategic research arrangement with City Therapeutics we invested in a convertible note, for which we elected the fair value option. For additional information on the arrangement with City Therapeutics, please read Note 19, Collaborative and Other Relationships, to these condensed consolidated financial statements.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


	Fair Value Measurements on a Recurring Basis
	As of December 31, 2024
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	1,664.9	$	—	$	1,664.9	$	—




Marketable equity securities	179.7		179.7		—		—
Other current assets:
Derivative contracts	62.5		—		62.5		—
Other non-current assets:

Plan assets for deferred compensation	42.8		—		42.8		—
Total	$	1,949.9	$	179.7	$	1,770.2	$	—
Liabilities:
Other current liabilities:
Derivative contracts	$	11.7	$	—	$	11.7	$	—
Contingent consideration obligations	291.2		—		—		291.2
Other non-current liabilities:

Contingent consideration obligations	221.6		—		—		221.6
Total	$	524.5	$	—	$	11.7	$	512.8

Our marketable equity securities represent investments in publicly traded equity securities. Our ability to liquidate our investment in Denali may be limited by the size of our interest, the volume of market-related activity, our concentrated level of ownership and potential restrictions resulting from our status as a collaborator. Therefore, we may realize significantly less than the current value of such investments.

In June 2025 Sage announced it entered into a definitive agreement for Supernus Pharmaceuticals, Inc. to acquire Sage, with the transaction expected to close in the third quarter of 2025.

As set forth in the amended Schedule 13D we filed with the SEC on July 30, 2025, we have disposed of all of our shares of Sage common stock in a block trade.

For additional information on our investments in Denali and Sage common stock, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in our 2024 Form 10-K.

There have been no material impairments of our assets measured and carried at fair value as of June 30, 2025 and December 31, 2024. In addition, there have been no changes to our valuation techniques as of June 30, 2025 and December 31, 2024.

For a description of our validation procedures related to prices provided by third-party pricing services and our option pricing valuation model, please read Note 1, Summary of Significant Accounting Policies - Fair Value Measurements, to our consolidated financial statements included in our 2024 Form 10-K.

Level 3 Assets and Liabilities Held at Fair Value

The following table presents quantitative information, as of the dates indicated, about the valuation techniques and significant unobservable inputs used in the valuation of our Level 3 financial assets and liabilities measured at fair value on a recurring basis:

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Quantitative Information about Level 3 Fair Value Measurements

As of June 30, 2025

(In millions)

Fair Value

Valuation Technique

Significant
Unobservable Input(s)

Range

Weighted Average

Liabilities:

Contingent consideration obligations

534.9

Discounted cash flow

Discount rate

5.6% - 5.7%

5.7

Expected timing of achievement of development milestones

2025 - 2030

—

Quantitative Information about Level 3 Fair Value Measurements

As of December 31, 2024

(In millions)

Fair Value

Valuation Technique

Significant
Unobservable Input(s)

Range

Weighted Average

Liabilities:

Contingent consideration obligations

512.8

Discounted cash flow

Discount rate

6.2% - 6.3%

6.2

Expected timing of achievement of development milestones

2025 - 2030

—

The weighted average discount rates were calculated based on the relative fair values of each distinct contingent consideration obligation related to our acquisition of HI-Bio in July 2024. In addition, we apply various probabilities of technological and regulatory success to the valuation models to estimate the fair values of these contingent consideration obligations, which ranged from approximately 70.0% to near certain probability as of June 30, 2025 and December 31, 2024.

There were no transfers of assets or liabilities into or out of Level 3 as of June 30, 2025 and December 31, 2024.

Contingent Consideration Obligations

In connection with our acquisition of HI-Bio in July 2024 we agreed to make additional payments based upon the achievement of certain milestone events. The following table provides a roll forward of the fair value of our contingent consideration obligations, which were classified as Level 3 measurements:



(In millions)	For the Three Months Ended June 30, 2025		For the Six Months Ended June 30, 2025
Fair value, beginning of period	$	522.4	$	512.8

Changes in fair value	13.2		22.8
Payments	(0.7)		(0.7)
Fair value, end of period	$	534.9	$	534.9

Changes in the fair value of our contingent consideration obligations are recorded in (gain) loss on fair value remeasurement of contingent consideration in our condensed consolidated statements of income. The fair values of the contingent consideration liabilities were based on a probability-adjusted discounted cash flow calculation using Level 3 fair value measurements and inputs. For additional information on the valuation techniques and inputs utilized in the valuation of our financial assets and liabilities, please read Note 1, Summary of Significant Accounting Policies, to our consolidated financial statements included in our 2024 Form 10-K.

As of June 30, 2025 and December 31, 2024, approximately $297.2 million and $291.2 million, respectively, of the fair value of the total contingent consideration obligations were classified as short-term and reflected as a component of accrued expense and other with the remaining $237.7 million and $221.6 million, respectively, reflected as a component of other long-term liabilities in our condensed consolidated balance sheets.

For the three and six months ended June 30, 2025, changes in the fair value of our contingent consideration obligations were primarily due to the passage of time.

During the second quarter of 2025 the first milestone related to the fourth patient dosed in a phase 3 clinical trial of felzartamab for AMR was achieved, resulting in a $150.0 million milestone payment made to the former shareholders of HI-Bio, which was substantially paid in July 2025.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Financial Instruments Not Carried at Fair Value

Other Financial Instruments

Due to the short-term nature of certain financial instruments, the carrying value reflected in our condensed consolidated balance sheets for current accounts receivable, due from anti-CD20 therapeutic programs, other current assets, accounts payable and accrued expense and other, approximates fair value.

Debt Instruments

The fair and carrying values of our debt instruments, which are Level 2 liabilities, are summarized as follows:


	As of June 30, 2025				As of December 31, 2024
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Current portion:


4.050% Senior Notes due September 15, 2025(1)	$	—	$	—	$	1,741.0	$	1,748.6
Current portion of notes payable	—		—		1,741.0		1,748.6

Non-current portion:


2.250% Senior Notes due May 1, 2030	1,351.1		1,495.2		1,295.6		1,494.7
5.050% Senior Notes due January 15, 2031(1)	407.1		397.8		—		—
5.750% Senior Notes due May 15, 2035(1)	668.7		645.5		—		—
5.200% Senior Notes due September 15, 2045	1,007.1		1,101.3		1,008.0		1,101.1
3.150% Senior Notes due May 1, 2050	946.0		1,475.3		943.7		1,475.0
3.250% Senior Notes due February 15, 2051	450.4		478.3		448.9		476.4
6.450% Senior Notes due May 15, 2055(1)	721.7		690.3		—		—
Non-current portion of notes payable	5,552.1		6,283.7		3,696.2		4,547.2
Total notes payable	$	5,552.1	$	6,283.7	$	5,437.2	$	6,295.8

(1) In May 2025 we issued our 2025 Senior Notes for an aggregate principal amount of $1.75 billion. In June 2025 we used the net proceeds from the sale of our 2025 Senior Notes to redeem in full our 4.050% Senior Notes due September 15, 2025, prior to maturity. For additional information, please read Note 13, Indebtedness, to these condensed consolidated financial statements.

The fair values of each of our series of Senior Notes were determined through market, observable and corroborated sources. The changes in the fair values of our Senior Notes as of June 30, 2025, compared to December 31, 2024, are primarily related to decreases in U.S. treasury yields, partially offset by increases in credit spreads used to value our Senior Notes since December 31, 2024. For additional information related to our Senior Notes, please read Note 13, Indebtedness, to our consolidated financial statements included in our 2024 Form 10-K.


Note 9:			Financial Instruments

The following table summarizes our financial assets with maturities of less than 90 days from the date of purchase included in cash and cash equivalents in our condensed consolidated balance sheets:


(In millions)	As of June 30, 2025		As of December 31, 2024


Money market funds	$	2,234.9	$	1,664.9


Total	$	2,234.9	$	1,664.9

The carrying value of our money market funds approximates fair value due to their short-term maturities.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Our marketable equity securities gains (losses) are recorded in other (income) expense, net in our condensed consolidated statements of income. The following tables summarize our marketable equity securities, classified as available-for-sale:


	As of June 30, 2025
(In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value












Marketable equity securities

Marketable equity securities, non-current	$	668.7	$	—	$	(511.7)	$	157.0
Total marketable equity securities	$	668.7	$	—	$	(511.7)	$	157.0


	As of December 31, 2024
(In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value












Marketable equity securities

Marketable equity securities, non-current	$	668.7	$	—	$	(489.0)	$	179.7
Total marketable equity securities	$	668.7	$	—	$	(489.0)	$	179.7

Strategic Investments

Our strategic investment portfolio includes investments in equity securities of certain biotechnology companies, which are reflected within our disclosures included in Note 8, Fair Value Measurements, to these condensed consolidated financial statements, as well as venture capital funds where the underlying investments are in equity securities of certain biotechnology companies and non-marketable equity securities.

As of June 30, 2025 and December 31, 2024, our strategic investment portfolio was comprised of investments totaling $224.0 million and $226.7 million, respectively, which are included in investments and other assets within our condensed consolidated balance sheets.

The decrease in our strategic investment portfolio as of June 30, 2025, compared to December 31, 2024, was primarily due to the decrease in the fair value of our investment in Denali common stock, partially offset by an increase in the fair value of our investment in Sage common stock.


Note 10:			Derivative Instruments

Foreign Currency Forward Contracts - Hedging Instruments

Due to the global nature of our operations, portions of our revenue and operating expense are recorded in currencies other than the U.S. dollar. The value of revenue and operating expense measured in U.S. dollars is therefore subject to changes in foreign currency exchange rates. We enter into foreign currency forward contracts and foreign currency options with financial institutions with the primary objective to mitigate the impact of foreign currency exchange rate fluctuations on our international revenue and operating expense.

Foreign currency forward contracts and foreign currency options in effect as of June 30, 2025 and December 31, 2024, had durations of 1 to 24 months and 1 to 12 months, respectively. These contracts have been designated as cash flow hedges and unrealized gains and losses on the portion of these foreign currency forward contracts and foreign currency options that are included in the effectiveness test are reported in AOCI. Realized gains and losses of such contracts and options are recognized in revenue when the sale of product in the currency being hedged is recognized and in operating expense when the expense in the currency being hedged is recorded. We recognize all cash flow hedge reclassifications from AOCI and fair value changes of excluded portions in the same line item in our condensed consolidated statements of income that have been impacted by the hedged item.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

The notional amount of foreign currency forward contracts and foreign currency options that were entered into to hedge forecasted revenue and operating expense is summarized as follows:


	Notional Amount
(In millions)	As of June 30, 2025		As of December 31, 2024
Euro	$	2,024.6	$	1,062.6
British pound	68.7		133.8
Swiss franc	128.5		—

Canadian dollar	20.4		38.6
Total foreign currency forward contracts and options	$	2,242.2	$	1,235.0

The pre-tax portion of the fair value of these foreign currency forward contracts and foreign currency options that were included in AOCI in total equity is summarized as follows:



(In millions)	As of June 30, 2025		As of December 31, 2024
Unrealized gains	$	17.9	$	50.6
Unrealized (losses)	(153.1)		(0.3)
Net unrealized gains (losses)	$	(135.2)	$	50.3

We expect net unrealized losses of approximately $135.2 million to be settled over the next 24 months, of which approximately $111.1 million of these net unrealized losses are expected to be settled over the next 12 months, with any amounts in AOCI to be reported as an adjustment to revenue or operating expense. We consider the impact of our and our counterparties’ credit risk on the fair value of the contracts as well as the ability of each party to execute its contractual obligations. As of June 30, 2025 and December 31, 2024, credit risk did not materially change the fair value of our foreign currency forward contracts and forward currency options.

The following tables summarize the effect of foreign currency forward contracts and forward currency options designated as hedging instruments in our condensed consolidated statements of income:


For the Three Months Ended June 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)					Net Gains/(Losses) Excluded from Effectiveness Testing and Recognized in Operating Income (in millions)
Location	2025		2024		Location	2025		2024
Revenue	$	(22.9)	$	7.6	Revenue	$	(0.8)	$	0.9
Operating expense	6.6		(4.9)		Operating expense	(0.8)		(0.7)

For the Six Months Ended June 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)					Net Gains/(Losses) Excluded from Effectiveness Testing and Recognized in Operating Income (in millions)
Location	2025		2024		Location	2025		2024
Revenue	$	(12.0)	$	10.5	Revenue	$	(0.4)	$	1.1
Operating expense	7.3		(7.0)		Operating expense	(1.8)		(1.9)

Foreign Currency Forward Contracts - Other Derivative Instruments

We also enter into other foreign currency forward contracts, usually with durations of one month or less, to mitigate the foreign currency risk related to certain balance sheet positions. We have not elected hedge accounting for these transactions.

The aggregate notional amount of these outstanding foreign currency forward contracts was $1,045.2 million and $738.7 million as of June 30, 2025 and December 31, 2024, respectively. Net gains of $27.7 million and $35.4 million related to these contracts were recorded as a component of other (income) expense, net for the three and six months ended June 30, 2025, respectively, compared to net losses of $5.7 million and $30.0 million, respectively, in the prior year comparative periods.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Summary of Derivative Instruments

While certain of our derivative instruments are subject to netting arrangements with our counterparties, we do not offset derivative assets and liabilities in our condensed consolidated balance sheets. The amounts in the table below would not be substantially different if the derivative assets and liabilities were offset.

The following table summarizes the fair value and presentation in our condensed consolidated balance sheets of our outstanding derivative instruments, including those designated as hedging instruments:


(In millions)	Balance Sheet Location	As of June 30, 2025		As of December 31, 2024
Cash Flow Hedging Instruments:
Asset derivative instruments	Other current assets	$	16.1	$	58.4

Liability derivative instruments	Accrued expense and other	118.9		0.3
	Other long-term liabilities	26.8		—





Other Derivative Instruments:
Asset derivative instruments	Other current assets	15.6		4.1
Liability derivative instruments	Accrued expense and other	4.8		11.4


Note 11:			Property, Plant and Equipment

Property, plant and equipment are recorded at historical cost, net of accumulated depreciation. Accumulated depreciation on property, plant and equipment was $2,808.7 million and $2,670.8 million as of June 30, 2025 and December 31, 2024, respectively. For the three and six months ended June 30, 2025, depreciation expense totaled approximately $66.9 million and $138.3 million, respectively, compared to $71.9 million and $141.2 million, respectively, in the prior year comparative periods.


Note 12:			Leases

New Corporate Headquarters Lease

In March 2025 we entered into a lease agreement with MIT Investment Management Company and BioMed Realty for the lease of approximately 580,000 square feet of office and research and development space located at 75 Broadway, Cambridge, Massachusetts, which will be used as our new global corporate headquarters, as well as integrating our research and development and technical operations teams alongside our North American commercial organization. As part of a multi-year real estate consolidation plan that is expected to result in a reduction of approximately 40% in our real estate footprint in Massachusetts, this new lease is intended to replace two existing leases, both in Cambridge, Massachusetts, including our current corporate headquarters. We expect the initial lease term of approximately 15.5 years to commence on May 31, 2028. The estimated minimum lease payments as a result of the new lease total approximately $1.5 billion over the initial lease term. We have an option to extend the lease for three extension periods of five years each and one six month short-term extension, at then market-based rates. We will account for this lease as a right-of-use asset and lease liability upon the lease commencement date.

For additional information on our accounting policies relating to leases, please read Note 1, Summary of Significant Accounting Policies - Leases, to our consolidated financial statements included in our 2024 Form 10-K.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)


Note 13:			Indebtedness

2025 Senior Notes

On May 12, 2025, we issued senior unsecured notes for an aggregate principal amount of $1.75 billion, consisting of the following:

•$400.0 million of 5.050% Senior Notes due January 15, 2031, valued at 99.981% of par;

•$650.0 million of 5.750% Senior Notes due May 15, 2035, valued at 99.924% of par; and

•$700.0 million of 6.450% Senior Notes due May 15, 2055, valued at 99.657% of par.

Our 2025 Senior Notes are senior unsecured obligations and may be redeemed at our option at any time at 100% of the principal amount plus accrued interest and, until a specified period before maturity, a specified make-whole amount. Our 2025 Senior Notes contain a change-of-control provision that, under certain circumstances, may require us to purchase our 2025 Senior Notes at a price equal to 101% of the principal amount plus accrued and unpaid interest to the date of repurchase.

We incurred approximately $13.9 million of costs associated with this offering which have been recorded as a reduction to the carrying amount of the debt on our condensed consolidated balance sheet. These costs will be amortized as additional interest expense using the effective interest rate method over the period from issuance through maturity. The discounts will be amortized as additional interest expense over the period from issuance through maturity using the effective interest rate method.

Interest on our 2031 Senior Notes is payable January 15 and July 15 of each year, commencing January 15, 2026. Interest on our 2035 Senior Notes and 2055 Senior Notes is payable May 15 and November 15 of each year, commencing on November 15, 2025.

4.050% Senior Notes due September 15, 2025

On September 15, 2015, we issued $1.75 billion aggregate principal amount of 4.050% Senior Notes due September 15, 2025, at 99.764% of par. In June 2025 we used the net proceeds from the sale of our 2025 Senior Notes to redeem our 4.050% Senior Notes due September 15, 2025, prior to their maturity. No gain or loss was recognized upon redemption.

2023 Term Loan Credit Agreement

In connection with our acquisition of Reata in September 2023 we entered into a $1.5 billion term loan credit agreement. On the closing date of the Reata acquisition we drew $1.0 billion from the 2023 Term Loan, comprised of a $500.0 million floating rate 364-day tranche and a $500.0 million floating rate three-year tranche. The remaining unused commitment of $500.0 million was terminated. As of December 31, 2023, we repaid $350.0 million of the 364--day tranche. The remaining $150.0 million portion of the 364-day tranche was repaid during the first quarter of 2024.

Additionally, during the first quarter of 2024 we repaid $250.0 million of the three-year tranche, with the remaining $250.0 million portion being subsequently repaid in full during the second quarter of 2024. For additional information on our acquisition of Reata, please read Note 2, Acquisitions, to our consolidated financial statements included in our 2024 Form 10-K.


Note 14:			Equity

Share Repurchases

In October 2020 our Board of Directors authorized our 2020 Share Repurchase Program, which is a program to repurchase up to $5.0 billion of our common stock. Our 2020 Share Repurchase Program does not have an expiration date. All shares repurchased under our 2020 Share Repurchase Program were retired. There were no share repurchases of our common stock during the three and six months ended June 30, 2025 and 2024. Approximately $2.1 billion remained available under our 2020 Share Repurchase Program as of June 30, 2025.

Table of Contents

BIOGEN INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(unaudited, continued)

Accumulated Other Comprehensive Income (Loss)

The following tables summarize the changes in AOCI, net of tax by component:


	For the Three Months Ended June 30, 2025
(In millions)	Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax		Currency Translation Adjustments, Net of Tax		Total
Balance, March 31, 2025	$	(6.2)	$	(16.2)	$	(152.1)	$	(174.5)
Other comprehensive income (loss) before reclassifications	(120.4)		0.6		41.6		(78.2)
Amounts reclassified from AOCI	14.6		—		—		14.6
Net current period other comprehensive income (loss)	(105.8)		0.6		41.6		(63.6)
Balance, June 30, 2025	$	(112.0)	$	(15.6)	$	(110.5)	$	(238.1)

	For the Six Months Ended June 30, 2025
(In millions)	Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax		Currency Translation Adjustments		Total
Balance, December 31, 2024	$	51.6	$	(16.6)	$	(171.2)	$	(136.2)
Other comprehensive income (loss) before reclassifications	(167.9)		1.0		60.7		(106.2)
Amounts reclassified from AOCI	4.3		—		—		4.3
Net current period other comprehensive income (loss)	(163.6)		1.0		60.7		(101.9)
Balance, June 30, 2025	$	(112.0)	$	(15.6)	$	(110.5)	$	(238.1)


	For the Three Months Ended June 30, 2024
(In millions)	Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax		Currency Translation Adjustments, Net of Tax		Total
Balance, March 31, 2024	$	(10.3)	$	(2.7)	$	(147.5)	$	(160.5)
Other comprehensive income (loss) before reclassifications	22.3		—		(5.6)		16.7
Amounts reclassified from AOCI	(2.2)		—		—		(2.2)
Net current period other comprehensive income (loss)	20.1		—		(5.6)		14.5
Balance, June 30, 2024	$	9.8	$	(2.7)	$	(153.1)	$	(146.0)

	For the Six Months Ended June 30, 2024
(In millions)	Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax		Currency Translation Adjustments		Total
Balance, December 31, 2023	$	(25.0)	$	(2.6)	$	(126.1)	$	(153.7)
Other comprehensive income (loss) before reclassifications	37.7		(0.1)		(27.0)		10.6
Amounts reclassified from AOCI	(2.9)		—		—		(2.9)
Net current period other comprehensive income (loss)	34.8		(0.1)		(27.0)		7.7
Balance, June 30, 2024	$	9.8	$	(2.7)	$	(153.1)	$

BIOGEN INC. 10-Q