10-K – 2026-02-06 – biib-20251231.htm

Samsung Bioepis Co., Ltd.
Joint Venture Agreement
In February 2012 we entered into a joint venture agreement with Samsung BioLogics establishing an entity, Samsung Bioepis, to develop, manufacture and market biosimilar products.
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 additional information on the sale of our equity interest in Samsung Bioepis, please read Note 3, Dispositions , to these consolidated financial statements.
2019 Development and Commercialization Agreement
In December 2019 we completed a transaction with Samsung Bioepis and secured the exclusive rights to commercialize two potential ophthalmology biosimilar products, BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS, and OPUVIZ, an aflibercept biosimilar referencing EYLEA, in major markets worldwide, including the U.S., Canada, Europe, Japan and Australia. The agreement established that Samsung Bioepis will be responsible for development and will supply both products to us at a pre-specified gross margin of approximately 45.0 %.
In October 2024 we notified Samsung Bioepis of our decision to terminate our 2019 Development and Commercialization Agreement (the DCA Agreement) solely within the U.S. and Canada. As a result of this termination we recognized impairment charges of approximately $ 20.2  million, which were recorded within amortization and impairment of acquired intangible assets within our consolidated statements of income for the year ended December 31, 2024. The transfer of commercialization rights for BYOOVIZ and OPUVIZ in the U.S. and Canada back to Samsung Bioepis was completed as of December 31, 2025.
In October 2025 we completed the sale of our remaining commercial rights to two ophthalmology assets in Europe: BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS, and OPUVIZ, an aflibercept biosimilar referencing EYLEA. Samsung Bioepis will have full responsibility for commercialization of BYOOVIZ upon the transfer of commercial rights from Biogen back to Samsung Bioepis, which became effective as of January 2026. Under the terms of this transaction, we received a payment of $ 28.0  million in November 2025 and recognized a minimal gain on disposal within our consolidated statements of income for the year ended December 31, 2025.
We reflected revenue on sales of BYOOVIZ to third parties in product revenue, net in our consolidated statements of income and recorded the related cost of revenue and sales and marketing expense in our consolidated statements of income to their respective line items when these costs were incurred.
2013 Commercial Agreement
In December 2013 we entered into an agreement with Samsung Bioepis to commercialize, over a 10-year term, three anti-TNF biosimilar product candidates which includes IMRALDI, an adalimumab biosimilar referencing HUMIRA, FLIXABI, an infliximab biosimilar referencing REMICADE, and BENEPALI, an etanercept biosimilar referencing ENBREL, in Europe. 
In July 2024 we exercised an option to extend this agreement by an additional five years and paid Samsung Bioepis an option exercise fee of $ 60.0 million, which was recorded within intangible assets, net within our consolidated balance sheets as of December 31, 2024.
We reflect revenue on sales of BENEPALI, IMRALDI and FLIXABI to third parties in product revenue, net in our consolidated statements of income and record the related cost of revenue and sales and marketing expense in our
F-68

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

consolidated statements of income to their respective line items when these costs are incurred. Royalty payments to AbbVie on sales of IMRALDI are recognized in cost of sales within our consolidated statements of income.
We share 50.0 % of the profit or loss related to our 2013 commercial agreement with Samsung Bioepis, which is recognized in collaboration profit sharing/(loss reimbursement) in our consolidated statements of income. For the years ended December 31, 2025, 2024 and 2023, we recognized net profit-sharing expense o f approximately $ 219.2 million , $ 227.4 million and $ 223.5 million, respectively, to reflect Samsung Bioepis' 50.0 % sharing of the net collaboration profits.
Other Services
Simultaneous with the formation of Samsung Bioepis, we also entered into a license agreement with Samsung Bioepis. Under this license agreement, we granted Samsung Bioepis an exclusive license to use, develop, manufacture and commercialize biosimilar products created by Samsung Bioepis using Biogen product-specific technology. In exchange, we receive single-digit royalties on biosimilar products developed and commercialized by Samsung Bioepis. Royalty revenue under the license agreement is recognized as a component of contract manufacturing, royalty and other revenue in our consolidated statements of income.
For the years ended December 31, 2025, 2024 and 2023, we recognized approximately $ 15.5 million , $ 14.4 million and $ 13.6 million, respectively, as a component of contract manufacturing, royalty and other revenue in our consolidated statements of income related to the license agreement.
Amounts receivable from Samsung Bioepis related to the agreements discussed above were approximately $ 4.4 million and $ 7.6 million as of December 31, 2025 and 2024, respectively. Amounts payable to Samsung Bioepis related to the agreements discussed above were approximately $ 42.7  million and $ 60.8  million as of December 31, 2025 and 2024, respectively.
Merz Therapeutics (previously Acorda Therapeutics, Inc.)
In June 2009 we entered into a collaboration and license agreement with Acorda to develop and commercialize products containing fampridine, such as FAMPYRA, in markets outside the U.S.
Under this agreement, we pay tiered royalties based on the level of ex-U.S. net sales and we may pay potential milestone payments based on the successful achievement of certain regulatory and commercial milestones.
In January 2024 we notified Acorda of our decision to terminate our collaboration and license agreement, effective January 1, 2025, whereby Acorda regained global commercialization rights to FAMPYRA. On April 1, 2024, Acorda filed for bankruptcy protection and announced its intention to sell substantially all of Acorda's assets to a third party. On July 10, 2024, Merz Therapeutics announced that its subsidiary Merz Pharmaceuticals LLC had completed the acquisition of FAMPYRA, and related assets from Acorda, and in 2025 we transitioned the global commercialization rights of FAMPYRA to Merz Therapeutics.
For the years ended December 31, 2024 and 2023, total cost of sales related to royalties and commercial supply of FAMPYRA reflected in our consolidated statements of income were approximately $ 52.4 million and $ 55.2 million, respectively.
Other Research and Discovery Arrangements and Funding Arrangements
These arrangements may include the potential for future milestone payments based on the achievement of certain clinical and commercial development payable over a period of several years.
Other
For the years ended December 31, 2025, 2024 and 2023, we recorded approximately $ 13.4 million , $ 54.0 million and $ 4.1 million, respectively, as research and development expense in our consolidated statements of income related to other research and discovery related arrangements.
Royalty Pharma Funding Arrangement
In February 2025 we entered into a funding agreement with Royalty Pharma under which we received $ 200.0 million in 2025 and will receive up to $ 50.0 million in 2026 to co-fund our development costs for the litifilimab program. As there is a substantive transfer of risk to the financial partner for the amount invested, the development funding will be recognized by us as an obligation to perform contractual services. This funding is being recognized as a reduction to research and development expense within our consolidated statements of income, proportionate to the related
F-69

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

expense. For the year ended December 31, 2025 , we recorded a reduction to research and development e xpense of $ 200.0 million within our consolidated statements of income.
If the litifilimab clinical trials are successful for the indications based on the applicable clinical trials, upon regulatory approval in the U.S. or certain major markets in the world, Royalty Pharma will be eligible to receive approval-based fixed milestone payments of up to $ 250.0 million. The milestone payments due upon approval will be recorded as a component of other (income) expense, net within our consolidated statements of income, when incurred.
If litifilimab receives regulatory approval, Royalty Pharma will be eligible to receive royalties of a mid-single digit percentage of the applicable net sales. Royalties on net sales will be recorded as cost of sales within our consolidated statements of income.
MorphoSys AG
As part of our acquisition of HI-Bio in July 2024, 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. These amounts included milestone payments due upon the first patient dosed in a Phase 3 clinical trial of felzartamab in a first and second indication of $ 35.0 million and $ 30.0 million, respectively.
During 2025 we made milestone payments to MorphoSys of $ 35.0 million and $ 30.0  million upon the first patient dosed in a Phase 3 clinical trial of felzartamab for the treatment of AMR and IgAN, respectively, which were recognized in acquired in-process research and development, upfront and milestone expense within our consolidated statements of income for the year ended December 31, 2025.
City Therapeutics, Inc.
In May 2025 we entered into a strategic research arrangement with City Therapeutics to develop select novel RNAi therapies. Through this arrangement, City Therapeutics will leverage its next-generation RNAi engineering technologies to develop an RNAi trigger molecule (or molecules) combined with our proprietary drug delivery technology. The collaboration will initially focus on a single target that mediates key CNS diseases, utilizing tissue enhanced delivery technologies with the aim of allowing for systemic administration of medicines. We will be responsible for IND-enabling studies and global clinical development along with any regulatory submissions and all activities related to commercialization, including manufacturing.
In connection with the closing of this transaction we made an upfront payment of $ 16.0 million to City Therapeutics, which was recognized in acquired in-process research and development, upfront and milestone expense within our consolidated statements of income for the year ended December 31, 2025 , and invested $ 30.0 million in exchange for a City Therapeutics convertible note, representing a minority equity interest in City Therapeutics, if converted. This convertible note was recorded as a component of investments and other assets within our consolidated balance sheets as of December 31, 2025.
We may also pay City Therapeutics potential research, development and sales-based milestone payments of up to $ 21.5 million, $ 360.0 million and $ 625.0 million, respectively, plus tiered royalties on potential future net sales, ranging from high-single digit to low-double digit percentages.
We also have the option to select one additional target in the collaboration, subject to an additional payment and availability of the target.
Dayra Therapeutics, Inc.
In October 2025 we entered into a research collaboration with Dayra to discover and develop oral macrocyclic peptides for priority targets in immunological conditions.
Under the terms of this agreement, both companies will collaborate to identify, validate and optimize oral macrocycle candidates for high-priority immunological targets, with our company advancing the molecules through further development and potential commercialization, including manufacturing.
In connection with the closing of this transaction we made an upfront payment of $ 50.0  million to Dayra, which was recognized in acquired in-process research and development, upfront and milestone expense within our consolidated statements of income for the year ended December 31, 2025.
F-70

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

This agreement also provides us with the option to acquire the development candidates from Dayra, subject to additional payments per program. Dayra will also be eligible to receive potential preclinical and clinical development milestone payments per program.
Vanqua Bio, Inc.
In October 2025 we entered into a license agreement with Vanqua granting us exclusive worldwide rights to further develop, manufacture and commercialize Vanqua's preclinical oral C5aR1 antagonist compound.
In connection with the closing of this transaction we made an upfront payment of $ 70.0  million to Vanqua, which was recognized in acquired in-process research and development, upfront and milestone expense within our consolidated statements of income for the year ended December 31, 2025.
We may pay Vanqua potential development, regulatory or commercial, and sales milestone payments of up to $ 135.0  million, $ 295.0  million and $ 560.0  million, respectively, if all the specified milestones set forth in this collaboration are achieved. In addition, we may pay Vanqua tiered royalties on potential net sales of any licensed product under this collaboration in the mid-single digit to low-double digit percentages.

Note 20:
Investments in Variable Interest Entities

Consolidated Variable Interest Entities
Our consolidated financial statements include the financial results of variable interest entities in which we are the primary beneficiary. The following are our significant variable interest entities.
Neurimmune SubOne AG
Beginning in 2007 we consolidated the results of Neurimmune as we determined we were the primary beneficiary because we had the power through the collaboration to direct the activities that most significantly impacted the entity's economic performance and we were required to fund 100.0 % of the research and development costs incurred in support of the collaboration. The collaboration and license agreement with Neurimmune was for the development and commercialization of antibodies for the potential treatment of Alzheimer's disease, including ADUHELM (as amended, the Neurimmune Agreement).
In November 2023 we notified Neurimmune of our decision to terminate the Neurimmune Agreement. Subsequent to the termination, we reconsidered our relationship with Neurimmune and determined that we were no longer the primary beneficiary of the variable interest entity. As a result, we recorded a net gain on the deconsolidation of Neurimmune of approximately $ 3.0  million, which was recorded in other (income) expense, net within our consolidated statements of income for the year ended December 31, 2023.
Research and development costs for which we reimbursed Neurimmune were reflected in research and development expense in our consolidated statements of income. For the year ended December 31, 2023, amounts reimbursed were immaterial.
Unconsolidated Variable Interest Entities
We have relationships with various variable interest entities that we do not consolidate as we lack the power to direct the activities that significantly impact the economic success of these entities. These relationships include investments in certain biotechnology companies and research collaboration agreements.
As of December 31, 2025 and 2024, the carrying value of our investments in certain biotechnology companies representing potential unconsolidated variable interest entities totaled $ 49.8  million and $ 23.6  million, respectively. The increase was primarily due to convertible note investments entered into during 2025, including a $ 30.0 million convertible note invested in City Therapeutics as part of our strategic research arrangement and a $ 5.0  million convertible note invested in Neela Therapeutics, Inc. For additional information on our arrangement with City Therapeutics, please read Note 19, Collaborative and Other Relationships , to these consolidated financial statements. Our maximum exposure to loss related to these variable interest entities is limited to the carrying value of our investments.
We have also entered into research collaboration agreements with certain variable interest entities where we are required to fund certain development activities. These development activities are included in research and
F-71

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

development expense in our consolidated statements of income as they are incurred. We have provided no financing to these variable interest entities other than previous contractually required amounts.

Note 21:
Litigation

We are currently involved in various claims, investigations and legal proceedings, including the matters described below. For information as to our accounting policies relating to claims and legal proceedings, including use of estimates and contingencies, please read Note 1, Summary of Significant Accounting Policies , to these consolidated financial statements.
With respect to some loss contingencies, an estimate of the possible loss or range of loss cannot be made until management has further information, including, for example, (i) which claims, if any, will survive dispositive motion practice; (ii) information to be obtained through discovery; (iii) information as to the parties' damages claims and supporting evidence; (iv) the parties’ legal theories; and (v) the parties' settlement positions. If an estimate of the possible loss or range of loss can be made at this time, it is included in the potential loss contingency description below.
The claims and legal proceedings in which we are involved also include challenges to the scope, validity or enforceability of the patents relating to our products, pipeline or processes and challenges to the scope, validity or enforceability of the patents held by others. These include claims by third parties that we infringe their patents. An adverse outcome in any of these proceedings could result in one or more of the following and have a material impact on our business or consolidated results of operations and financial position: (i) loss of patent protection; (ii) inability to continue to engage in certain activities; and (iii) payment of significant damages, royalties, penalties and/or license fees to third parties.
Loss Contingencies
Securities Litigation
We and certain current and former officers are defendants in three securities actions pending in the District Court, one filed by Nadia Shash and Amjad Khan in November 2020, which relates to statements about ADUHELM, one filed by the Oklahoma Firefighters Pension and Retirement System in February 2022, which relates to statements about ADUHELM, and one filed by Thomas Allen Gray in June 2024, which relates to statements about LEQEMBI, TECFIDERA and VUMERITY. All allege violations of federal securities laws under 15 U.S.C. §78j(b) and §78t(a) and 17 C.F.R. §240.10b-5 and seek declarations of the actions as class actions and monetary relief.
Derivative Actions
We and members of the Board of Directors are named as defendants in five derivative actions pending in the District Court, one filed by The Booth Family Trust (Booth) in February 2022, one filed by Elaine Wang (Wang) in July 2022, one filed by Jonathan Blaufarb (Blaufarb I) in July 2024, one filed by Lawrence Hollin (Hollin) in October 2024 and one filed by Jonathan Blaufarb (Blaufarb II) in October 2024. The Booth, Wang and Blaufarb II actions relate to ADUHELM and other matters, and the Blaufarb I and Hollin actions relate to statements about LEQEMBI, our compliance controls, 2023 earnings guidance and other matters. The actions allege breach of fiduciary duty, waste of corporate assets and other common law claims, and violations of the Securities Exchange Act of 1934, 15 U.S.C. §78a et seq. The actions seek declaratory and injunctive relief, monetary relief payable to Biogen, and attorneys’ fees and costs payable to the plaintiffs. All derivative actions are stayed.
IMRALDI Patent Litigation
IMRALDI is an adalimumab biosimilar manufactured by Samsung Bioepis that Biogen commercializes in Europe.
In June 2022, Fresenius Kabi filed a claim for damages and injunctive relief against Biogen France SAS in the Tribunal de Grande Instance de Paris alleging infringement of the French counterpart of EP ‘3 145 488 Patent (the EP '488 Patent) by a formulation of IMRALDI no longer commercialized in France. Fresenius Kabi alleges damages of € 13,450,000 plus interest and costs. Biogen disputes infringement and the validity of the patent. Trial is set for June 2026.
In May 2025 the Higher Regional Court of Düsseldorf, Germany held that a formulation of IMRALDI we no longer commercialize in Germany infringed the German counterpart of the EP '488 Patent, enjoined infringement and declared Fresenius Kabi's right to seek damages. Biogen has requested review of the decision by Germany's Federal Court of Justice and has challenged the validity of the patent in a separate proceeding.
F-72

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Litigation with Former Convergence Shareholders
In 2015 Biogen acquired Convergence, a U.K. company. In 2019 Shareholder Representative Services LLC, on behalf of former shareholders of Convergence, asserted claims of $ 200.0  million for alleged breaches of the contract pursuant to which we acquired Convergence and in June 2023 it and former Convergence shareholders filed a suit against us in the High Court of Justice of England and Wales asserting one of the 2019 claims and seeking payment of $ 49.9  million, plus interest and costs. The parties have reached an agreement in principle to resolve all claims relating to Biogen's acquisition of Convergence.
Humana Patient Assistance Litigation
In February 2025 Humana filed suit against Biogen Inc., Biogen U.S. Corp. and Advanced Care Scripts, Inc. in Jefferson Circuit Court in Kentucky alleging damages related to providing MS patients with free medications and to charitable contributions to non-profit organizations that provide financial assistance to MS patients. Humana alleges breach of contract, fraud and other claims under various state laws and seeks damages, attorneys' fees and costs.
Genentech Litigation
In February 2023 Genentech Inc. filed suit in the U.S. District Court for the Northern District of California claiming that it was owed royalties on sales of TYSABRI that occurred after the expiration of a patent licensed by Genentech to Biogen. In November 2025 the court entered judgment against us for approximately $ 124.3  million. We appealed and the appeal is pending.
Lender Litigation
In April 2025, by agreement of the parties, the Supreme Court of the State of New York discontinued with prejudice the suit filed in 2024 by BioPharma Credit PLC, BPCR Limited Partnership, and BioPharma Credit Investments V (Master) LP against us and Reata Pharmaceuticals, Inc. alleging breach of a loan agreement.
Antitrust Litigation
In October 2025 Local No. 1 Health Fund, the Mayor and City Council of Baltimore, Teamsters Local 237 Welfare Fund, Teamsters Local 237 Retirees' Benefit Fund, UFCW Local 1500 Welfare Fund, and Jacksonville Police Officers and Fire Fighters Health Insurance Trust filed an amended complaint against us in now consolidated proceedings in the U.S. District Court for the Northern District of Illinois (the Illinois federal court). The first complaint was filed in August 2024. The plaintiffs allege violations of federal antitrust laws including 15 U.S.C. §§ 1, 2 and 13(c), the Racketeer Influenced and Corrupt Organizations Act, 18 U.S.C. §1962(c) and of various state laws, based on allegations about our contracts with pharmacy benefit managers related to TECFIDERA and VUMERITY and other allegations. Plaintiffs seek declarations of the actions as class actions, monetary, declaratory and equitable relief, and attorneys' fees and costs.
In addition, in September 2025 Walgreen Co. and The Kroger Co. sued us in the Illinois federal court, alleging violations of 15 U.S.C. §§ 1 and 2 based on allegations about our contracts with pharmacy benefit managers related to TECFIDERA and VUMERITY and other allegations. They seek monetary, declaratory and equitable relief, and attorneys' fees and costs.
Neurimmune Litigation
In May 2025 we sued Neurimmune Holding AG and Neurimmune Subone AG (collectively, "Neurimmune") in the District Court seeking declaratory judgment and permanent injunctive relief regarding our rights under a terminated collaboration agreement related to aducanumab. In September 2025 Neurimmune counterclaimed for declaratory judgment, breach of contract and unfair competition under Massachusetts G.L. 93A and seeking monetary, declaratory and equitable relief and attorneys' fees and costs.
TECFIDERA E.U. Litigation
In November 2023 we sued Neuraxpharm Pharmaceuticals S.L. and Neuraxpharm Netherlands B.V. (collectively, Neuraxpharm), Zaklady Farmaceutyzne Polpharma S.A. (Polpharma), Sandoz B.V. (Sandoz), Mylan Ireland Ltd. and Mylan B.V. in the District Court of Amsterdam Netherlands for damages for sales of generic versions of TECFIDERA in violation of our regulatory marketing protection. Neuraxpharm, Polpharma and Sandoz counterclaimed for damages based on our actions to enforce TECFIDERA's regulatory marketing protection.
F-73

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

In June 2024 we sued Sandoz A/S in the Danish Maritime and Commercial High Court for damages for sales of its generic version of TECFIDERA in violation of our regulatory marketing protection. Sandoz A/S counterclaimed for damages based on our actions to enforce TECFIDERA's regulatory marketing protection. These cases are stayed.
In September 2025 the European General Court annulled the May 2023 European Commission decision granting TECFIDERA an additional year of regulatory marketing protection extending until February 2025. We and the European Commission appealed and the appeal is pending.
Germany Tax Matter
In December 2025 and January 2026 a German tax authority issued assessments against us of approximately $ 246.5  million including interest, which continues to accrue. We are challenging the assessments.
Other Matters
Government Investigations
In April 2025 the SEC Division of Enforcement informed us that it has closed the matter in which we had received subpoenas seeking information relating to ADUHELM and its launch and our equity plans, and in April and May 2025 the DOJ and SEC informed us that they closed the matters in which we had received subpoenas seeking information relating to our business operations in several foreign countries.
In May 2024 the Italian Competition Authority informed us that it is investigating Biogen and other companies in relation to our biosimilar product BYOOVIZ.
In September 2025 we received a Civil Investigative Demand from the Louisiana Department of Justice for information regarding our policies relating to the purchase of drugs by healthcare organizations that are covered entities under Section 340B of the Public Health Service Act.
In January 2026 we received a request for information regarding TECFIDERA from the European Commission Directorate-General for Competition.
TYSABRI Biosimilar Patent Matter
In September 2022 we filed an action in the U.S. District Court for the District of Delaware against Sandoz Inc., other Sandoz entities and Polpharma Biologics S.A. under the Biologics Price Competition and Innovation Act, 42 U.S.C. §262, seeking a declaratory judgment of patent infringement. Trial against Sandoz Inc. is scheduled for April 2027.
Hatch-Waxman Act Litigation relating to VUMERITY Orange-Book Listed Patents
In July 2023 Biogen and Alkermes Pharma Ireland Limited filed patent infringement proceedings relating to VUMERITY Orange-Book listed patents (U.S. Patent Nos. 8,669,281, 9,090,558 and 10,080,733) pursuant to the Drug Price Competition and Patent Term Restoration Act of 1984 (the Hatch-Waxman Act) in the U.S. District Court for the District of Delaware against Zydus Worldwide DMCC, Zydus Pharmaceuticals (USA) Inc. and Zydus Lifesciences Limited. In July 2025 the parties reached a settlement and the court dismissed the case pursuant to the parties' stipulation of dismissal.
Eisai Matter
In June 2025 we filed a request for arbitration in the International Court of Arbitration of the International Chamber of Commerce seeking adoption of a budget and commercialization plan for the European Territory that allocates commercialization activities to Biogen and Eisai in an equitable fashion taking into account our respective capabilities and provides a meaningful role for each party.
Product Liability and Other Legal Proceedings
We are also involved in product liability claims and other legal proceedings incidental to our normal business activities. While the outcome of any of these proceedings cannot be accurately predicted, we do not believe the ultimate resolution of any of these existing matters would have a material adverse effect on our business or financial condition.
F-74

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Note 22:
Commitments and Contingencies

Royalty Payments
TYSABRI
We are obligated to make contingent payments of 18.0 % on annual worldwide net sales of TYSABRI up to $ 2.0 billion and 25.0 % on annual worldwide net sales of TYSABRI that exceed $ 2.0 billion. Royalty payments are recognized as cost of sales in our consolidated statements of income.
SPINRAZA
We make royalty payments to Ionis on annual worldwide net sales of SPINRAZA using a tiered royalty rate between 11.0 % and 15.0 %, which are recognized in cost of sales within our consolidated statements of income.
For additional information on our collaboration arrangements with Ionis, please read Note 19, Collaborative and Other Relationships , to these consolidated financial statements.
QALSODY
We make royalty payments to Ionis on annual worldwide net sales of QALSODY using a tiered royalty rate between 11.0 % and 15.0 %, which are recognized in cost of sales within our consolidated statements of income.
For additional information on our collaboration arrangements with Ionis, please read Note 19, Collaborative and Other Relationships , to these consolidated financial statements.
VUMERITY
We make royalty payments to Alkermes on worldwide net sales of VUMERITY using a royalty rate of 15.0 % on product that Alkermes has manufactured and 16.0 % on product manufactured by us or a third-party designee, which are recognized as cost of sales in our consolidated statements of income.
SKYCLARYS
In connection with our acquisition of Reata in September 2023 we assumed additional contractual obligations related to royalty payments. Reata entered into agreements to pay royalties on annual worldwide net sales of SKYCLARYS, which will cumulatively range in the low to mid-single digit percentages. Royalty payments are recognized as cost of sales in our consolidated statements of income.
For additional information on our acquisition of Reata, please read Note 2, Acquisitions , to these consolidated financial statements.
Lease Commitments
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.
For additional information on our leases, please read Note 12, Leases , to these consolidated financial statements.
Contingent Consideration related to Business Combinations
In connection with our acquisition of HI-Bio in July 2024 we may make additional payments based upon the achievement of certain milestone events. We recognized the contingent consideration obligations associated with this acquisition at its fair value on the acquisition date and we revalue this obligation each reporting period. We may pay up to a total of $ 650.0 million in contingent development and regulatory milestone payments. The acquisition-date fair value of these milestones was approximately $ 485.1 million.
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 paid during the third quarter of 2025. In October 2025 the second milestone related to the fourth patient dosed in a Phase 3 clinical trial of felzartamab for IgAN was achieved, resulting in a
F-75

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

$ 150.0 million milestone payment made to the former shareholders of HI-Bio, which was paid during the fourth quarter of 2025.
For additional information on our acquisition of HI-Bio, please read Note 2, Acquisitions , to these consolidated financial statements.
Contingent Development, Regulatory and Commercial Milestone Payments
Based on our development plans as of December 31, 2025, we could make potential future milestone payments to third parties of up to approximately $ 5.3 billion, including approximately $ 0.7 billion in development milestones, approximately $ 0.8 billion in regulatory milestones and approximately $ 3.8 billion in commercial milestones, as part of our various collaborations, including licensing and development programs. Payments under these agreements generally become due and payable upon achievement of certain development, regulatory or commercial milestones. Because the achievement of these milestones was not considered probable as of December 31, 2025, such contingencies have not been recorded in our financial statements. Amounts related to contingent milestone payments are not considered contractual obligations as they are contingent on the successful achievement of certain development, regulatory or commercial milestones.
If certain research milestones are met, we may pay up to approximately $ 67.5  million in additional milestones in 2026 under our current agreements, excluding opt-in payments. This amount includes a $ 45.0  million milestone payment due upon the initiation of a Phase 3 trial of salanersen.
Other Funding Commitments
As of December 31, 2025, we have several ongoing clinical studies in various clinical trial stages. Our most significant clinical trial expenditures are to CROs. The contracts with CROs are generally cancellable, with notice, at our option. We recorded accrued expense of approximately $ 39.3 million in our consolidated balance sheets for expenditures incurred by CROs as of December 31, 2025. We have approximately $ 524.9 million in cancellable future commitments based on existing CRO contracts as of December 31, 2025.
Tax Related Obligations
We exclude liabilities pertaining to uncertain tax positions from our summary of contractual obligations as we cannot make a reliable estimate of the period of cash settlement with the respective taxing authorities. As of December 31, 2025, we have approximately $ 166.8 million of liabilities associated with uncertain tax positions.
As of December 31, 2024, we accrued income tax liabilities of approximately $ 234.0 million under the Transition Toll Tax, which was subsequently paid in full in April 2025. For additional information on the Transition Toll Tax, please read Note 17, Income Taxes , to these consolidated financial statements.

Note 23:
Guarantees

As of December 31, 2025 and 2024, we did not have significant liabilities recorded for guarantees.
We enter into indemnification provisions under our agreements with other companies in the ordinary course of business, typically with business partners, contractors, clinical sites and customers. Under these provisions, we generally indemnify and hold harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of our activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments we could be required to make under these indemnification provisions is unlimited. However, to date we have not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these agreements is minimal. Accordingly, we have no liabilities recorded for these agreements as of December 31, 2025 and 2024.

Note 24:
Employee Benefit Plans

We sponsor various retirement and pension plans. Our estimates of liabilities and expense for these plans incorporate a number of assumptions, including expected rates of return on plan assets and interest rates used to discount future benefits.
F-76

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

401(k) Savings Plan
We maintain a 401(k) Savings Plan, which is available to substantially all regular employees in the U.S. over the age of 21 . Participants may make voluntary contributions. We make matching contributions according to the 401(k) Savings Plan’s matching formula. All matching contributions and participant contributions vest immediately. The 401(k) Savings Plan also holds certain transition contributions on behalf of participants who previously participated in the Biogen, Inc. Retirement Plan. The expense related to our 401(k) Savings Plan primarily consists of our matching contributions.
Expense related to our 401(k) Savings Plan totaled approximately $ 52.6 million, $ 51.5 million and $ 55.9 million for the years ended December 31, 2025, 2024 and 2023, respectively.
Deferred Compensation Plan
We maintain a non-qualified deferred compensation plan, known as the SSP, which allows a select group of management employees in the U.S. to defer a portion of their compensation. The SSP also provides certain credits to highly compensated U.S. employees that are paid by the company. These credits are known as the Restoration Match. The deferred compensation amounts are accrued when earned. Such deferred compensation is distributable in cash in accordance with the rules of the SSP. Deferred compensation amounts under such plan as of December 31, 2025 and 2024, totaled approximately $ 152.8 million and $ 140.6 million, respectively, and are included in other long-term liabilities in our consolidated balance sheets. The SSP also holds certain transition contributions on behalf of participants who previously participated in the Biogen, Inc. Retirement Plan. The Restoration Match and participant contributions vest immediately. Distributions to participants can be either in one lump sum payment or annual installments as elected by the participants.
Pension Plans
Our retiree benefit plans include defined benefit plans for employees in our affiliates in Switzerland and Germany as well as other insignificant defined benefit plans in certain other countries where we maintain an operating presence.
Our Swiss plan is a government-mandated retirement fund that provides employees with a minimum investment return. The minimum investment return is determined annually by the Swiss government and was 1.75 % in 2025, 1.00 % in 2024 and 1.75 % in 2023. Under the Swiss plan, both we and certain of our employees with annual earnings in excess of government determined amounts are required to make contributions into a fund managed by an independent investment fiduciary. Employer contributions must be in an amount at least equal to the employee’s contribution. Minimum employee contributions are based on the respective employee’s age, salary and gender. As of December 31, 2025 and 2024, the Swiss plan had an unfunded net pension obligation of $ 72.9 million and $ 61.5 million, respectively, and plan assets that totaled $ 285.3 million and $ 224.7 million, respectively. In 2025, 2024 and 2023 we recognized net expense totaling $ 16.8 million, $ 17.5 million and $ 17.6 million, respectively, related to our Swiss plan, of which $ 7.5 million, $ 6.0 million and $ 5.1 million, respectively, was included in other (income) expense, net in our consolidated statements of income.
The obligations under the German plans are unfunded and totaled $ 45.8 million and $ 45.6 million as of December 31, 2025 and 2024, respectively. Net periodic pension cost related to the German plans totaled $ 3.9 million, $ 3.8 million and $ 3.6 million for the years ended December 31, 2025, 2024 and 2023, respectively, of which $ 1.2 million, $ 1.1 million and $ 0.8 million, respectively, was included in other (income) expense, net in our consolidated statements of income.

Note 25:
Segment Information

We operate and are managed as one operating segment, and derive revenue from activities related to the discovery, development and delivery of innovative therapies for people living with serious and complex diseases.
Our research and development organization is responsible for the research and discovery of new product candidates and supports development and registration efforts for potential future products. Our pharmaceutical, operations and technology organization manages the development of the manufacturing processes, clinical trial supply, commercial product supply, distribution, buildings and facilities. Our commercial organization is responsible for U.S. and international development of our commercial products. We are also supported by corporate staff functions.
Our CEO, as the CODM, manages and allocates resources to the operations of our company on a total company basis by assessing the overall level of resources available and deciding how to best deploy these resources across
F-77

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

functions, therapeutic areas and research and development projects that are in line with our long-term company-wide strategic goals. In making these decisions, our CEO is provided with and uses consolidated financial information for purposes of evaluating performance, forecasting future period financial results, allocating resources and setting incentive targets. The CODM performs this assessment based on the segment’s net income. Through this analysis, which includes a comparison to budgeted results, the CODM assesses performance and how to allocate resources across the functions discussed above. The measure of segment assets used in determining how to manage and allocate resources is reported within our consolidated balance sheets as total assets.
The tables presented below, which were prepared in accordance with the accounting policies discussed in Note 1, Summary of Significant Accounting Policies , contain additional information on enterprise-wide disclosures about product revenue, other revenue and long-lived assets, as well as our segment’s revenue and profits, including significant segment expense and other segment items. Revenue is primarily attributed to individual countries based on location of the customer or licensee.
Geographic Information
The following tables contain certain financial information by geographic area:

December 31, 2025
(In millions) U.S. Europe (1)
Germany Asia Other Total
Product revenue from external customers $ 3,547.9   $ 1,871.6   $ 853.0   $ 419.1   $ 427.8   $ 7,119.4  
Revenue from anti-CD20 therapeutic programs 1,775.4   1.8   —   —   83.4   1,860.6  

Contract manufacturing, royalty and other revenue 414.7   10.8   —   307.4   —   732.9  
Long-lived assets 1,236.7   2,053.8   12.2   5.9   12.2   3,320.8  

December 31, 2024
(In millions) U.S. Europe (1)
Germany Asia Other Total
Product revenue from external customers $ 3,237.3   $ 2,171.5   $ 955.6   $ 366.9   $ 482.2   $ 7,213.5  
Revenue from anti-CD20 therapeutic programs 1,673.6   0.6   —   —   75.7   1,749.9  

Contract manufacturing, royalty and other revenue 395.0   0.4   —   257.2   —   652.6  
Long-lived assets 1,366.1   2,139.2   13.3   8.5   10.6   3,537.7  

December 31, 2023
(In millions) U.S. Europe (1)
Germany Asia Other Total
Product revenue from external customers $ 3,141.4   $ 2,127.4   $ 868.0   $ 649.4   $ 460.5   $ 7,246.7  
Revenue from anti-CD20 therapeutic programs 1,618.5   0.4   —   —   70.7   1,689.6  
Contract manufacturing, royalty and other revenue 673.6   11.7   —   214.0   —   899.3  
Long-lived assets 1,443.0   2,248.0   17.5   8.3   12.9   3,729.7  

(1) Represents amounts related to Europe less those attributable to Germany.
Long-Lived Assets
As of December 31, 2025, 2024 and 2023, approximately $ 2.0 billion, $ 2.1 billion and $ 2.2 billion, respectively, of our long-lived assets were related to the construction of our large-scale biologics manufacturing facility in Solothurn, Switzerland.
F-78

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Additional Segment Information
The following table includes additional information about reported segment revenue, significant segment expense and segment measure of profitability:

For the Years Ended December 31,
(In millions) 2025 2024 2023
Total revenue $ 9,890.6   $ 9,675.9   $ 9,835.6  
Less cost and expense:
Cost of sales, excluding amortization and impairment of acquired intangible assets:
Product cost of sales 1,587.2   1,604.2   1,787.2  
Royalty cost of sales 817.0   706.2   746.2  
Research and development:
Research and discovery 183.2   201.5   212.5  
Early stage programs 257.7   286.6   361.0  
Late stage programs 232.0   209.7   250.5  
Marketed products 412.8   534.7   766.1  
Other research and development costs (1)
692.9   747.8   855.3  
Acquired in-process research and development, upfront and milestone expense 471.8   61.5   16.6  
Selling, general and administrative 2,433.6   2,403.7   2,549.7  
Other segment expense (2)
1,509.5   1,287.8   1,129.4  
Net Income attributable to Biogen Inc. $ 1,292.9   $ 1,632.2   $ 1,161.1  

(1) Other research and development costs primarily consist of indirect costs incurred in support of overall research and development activities and non-specific programs, including activities that benefit multiple programs, such as management costs, as well as depreciation, information technology and facility-based expenses and are not allocated to a specific program or stage.
(2) Other segment expense includes: amortization and impairment of acquired intangible assets; collaboration profit sharing/(loss reimbursement); (gain) loss on fair value remeasurement of contingent consideration; impairment of ROU asset; restructuring charges; gain on sale of priority review voucher, net; other (income) expense, net; income tax (benefit) expense; and net income attributable to noncontrolling interests, net of tax.
F-79

Table of Contents

Report of Independent Registered Public Accounting Firm
To the Board of Directors and Shareholders of Biogen Inc.

Opinions on the Financial Statements and Internal Control over Financial Reporting
We have audited the accompanying consolidated balance sheets of Biogen Inc. and its subsidiaries (the “Company”) as of December 31, 2025 and 2024, and the related consolidated statements of income, of comprehensive income, of equity and of cash flow for each of the three years in the period ended December 31, 2025, including the related notes (collectively referred to as the “consolidated financial statements”). We also have audited the Company's internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).
In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by the COSO.
Basis for Opinions
The Company's management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in Management’s Annual Report on Internal Control over Financial Reporting appearing under Item 9A. Our responsibility is to express opinions on the Company’s consolidated financial statements and on the Company's internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.
We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.
Our audits of the consolidated financial statements included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.
Definition and Limitations of Internal Control over Financial Reporting
A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.
F-80

Table of Contents

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.
Critical Audit Matters
The critical audit matter communicated below is a matter arising from the current period audit of the consolidated financial statements that was communicated or required to be communicated to the audit committee and that (i) relates to accounts or disclosures that are material to the consolidated financial statements and (ii) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.
Reserves for Medicaid and Managed Care Rebates in the U.S.
As described in Notes 1 and 5 to the consolidated financial statements, the Company recognized revenue from product sales, net of reserves, including contractual adjustments related to Medicaid and managed care rebates in the U.S. Within accrued expense and other, revenue-related reserves amounted to $1,000.4 million as of December 31, 2025. A portion of this balance includes contractual adjustments for Medicaid and managed care rebates in the U.S. Medicaid rebates relate to the Company’s estimated obligations to states under established reimbursement arrangements. The Company’s liability for Medicaid rebates consists of estimates for claims that a state will make for the current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, invoices received for claims from the prior quarters that have not been paid and an estimate of potential claims that will be made for inventory that exists in the distribution channel at period end. Managed care rebates in the U.S. represent the Company’s estimated obligations to third-parties, primarily pharmacy benefit managers. These rebates result from performance-based goals, formulary position and price increase limit allowances (price protection). The calculation of the accrual for these rebates is based on an estimate of the coverage patterns and the resulting applicable contractual rebate rate(s) to be earned over a contractual period. Rebate accruals for Medicaid and managed care in the U.S. are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expense and other current liabilities. The estimates of the reserves for Medicaid and managed care in the U.S. reflect historical experience, current contractual and statutory requirements, specific known market events and trends, industry data and forecasted customer buying and payment patterns.
The principal considerations for our determination that performing procedures relating to reserves for Medicaid and managed care rebates in the U.S. is a critical audit matter are (i) the significant judgment by management due to the significant measurement uncertainty when developing the estimate of the reserves and (ii) a high degree of auditor judgment, subjectivity, and effort in performing procedures and evaluating management's significant assumptions related to historical experience, current contractual requirements, specific known market events, and forecasted customer buying and payment patterns.
Addressing the matter involved performing procedures and evaluating audit evidence in connection with forming our overall opinion on the consolidated financial statements. These procedures included testing the effectiveness of controls relating to management's estimate of the reserves for Medicaid and managed care rebates in the U.S. These procedures also included, among others (i) developing an independent estimate of the reserves for Medicaid and managed care rebates in the U.S. by utilizing third-party data related to product demand, data related to price changes, the terms of the specific rebate programs, the historical trend of actual rebate claims paid and consideration of contractual requirement changes and market events; (ii) comparing the independent estimate to management’s estimate to evaluate the reasonableness of management's estimate; and (iii) testing, on a sample basis, rebate claims paid by the Company, including evaluating the claims for consistency with the contractual terms of the Company’s rebate agreements.
/s/ PricewaterhouseCoopers LLP
Boston, Massachusetts
February 6, 2026

We have served as the Company's auditor since 2003.
F-81