Cover and table of contents

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

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

For the fiscal year ended December 31, 2025

or

☐			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

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes x No o

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o No x

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			x						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. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. x

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant's executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

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

The aggregate market value of the registrant’s common stock held by non-affiliates of the registrant (without admitting that any person whose shares are not included in such calculation is an affiliate) computed by reference to the price at which the common stock was last sold as of the last business day of the registrant’s most recently completed second fiscal quarter was $18,378,285,308.

As of February 4, 2026, the registrant had 146,758,528 shares of common stock, $0.0005 par value, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the definitive proxy statement for our 2026 Annual Meeting of Stockholders are incorporated by reference into Part III of this report.

BIOGEN INC.

ANNUAL REPORT ON FORM 10-K

For the Year Ended December 31, 2025

TABLE OF CONTENTS

						Page
PART I
Item 1.			Business			1
Item 1A.			Risk Factors			39
Item 1B.			Unresolved Staff Comments			54
Item 1C.			Cybersecurity			54
Item 2.			Properties			55
Item 3.			Legal Proceedings			56
Item 4.			Mine Safety Disclosures			56
PART II
Item 5.			Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities			57
Item 6.			Reserved			58
Item 7.			Management’s Discussion and Analysis of Financial Condition and Results of Operations			59
Item 7A.			Quantitative and Qualitative Disclosures About Market Risk			93
Item 8.			Financial Statements and Supplementary Data			94
Item 9.			Changes in and Disagreements with Accountants on Accounting and Financial Disclosure			94
Item 9A.			Controls and Procedures			94
Item 9B.			Other Information			95
Item 9C.			Disclosure Regarding Foreign Jurisdictions that Prevent Inspections			95
PART III
Item 10.			Directors, Executive Officers and Corporate Governance			96
Item 11.			Executive Compensation			96
Item 12.			Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters			96
Item 13.			Certain Relationships and Related Transactions, and Director Independence			96
Item 14.			Principal Accountant Fees and Services			96
PART IV
Item 15.			Exhibits and Financial Statement Schedules			97
Item 16.			Form 10-K Summary			97
Signatures						100
Consolidated Financial Statements						F- 1

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 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 and governments;

• 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 and uncertainties, 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 and a biosimilar entrant of TYSABRI;

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

• 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 salanersen;

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

• 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 Supernus, as well as the potential therapeutic scope of the development and commercialization of our and our collaborators’ 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, preclinical 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., and China and other countries, regions affected by Russia's invasion of Ukraine and the military conflict in the Middle East;

• 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;

• 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 or executive 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, including actions related to MFN drug pricing;

• 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 and RTP facilities;

• 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; and

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

These forward-looking statements involve risks and uncertainties, including those that are described in Item 1A. Risk Factors and Item 7. 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 this Annual Report on 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®, PLEGRIDY®, QALSODY®, RITUXAN®, RITUXAN HYCELA®, SKYCLARYS®, SPINRAZA®, TECFIDERA®, THECAFLEX DRX®, TYSABRI® and VUMERITY® are registered trademarks of Biogen.

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

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

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 Omnibus Equity Plan			Biogen Inc. 2024 Omnibus Equity Plan
2017 Omnibus Equity Plan			Biogen Inc. 2017 Omnibus Equity Plan
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
AAIC			Alzheimer's Association International Conference
AbbVie			AbbVie Inc.
Acorda			Acorda Therapeutics, Inc.
AI			Artificial Intelligence
Alcyone			Alcyone Therapeutics, Inc.
Alkermes			Alkermes plc
ALS			Amyotrophic Lateral Sclerosis
AMP			Average Manufacturer Price
AMR			Antibody-Mediated Rejection
AOCI			Accumulated Other Comprehensive Income (Loss)
ASO			Antisense Oligonucleotide
ASU			Accounting Standards Update
BLA			Biologics License Application
Blackstone			Blackstone Life Sciences
CCPA			California Consumer Privacy Act
CEO			Chief Executive Officer
CHMP			Committee for Medicinal Products for Human Use
CISO			Chief Information Security Officer
CLE			Cutaneous Lupus Erythematosus
CLL			Chronic Lymphocytic Leukemia
CMS			Centers for Medicare & Medicaid Services
CNS			Central Nervous System
CODM			Chief Operating Decision Maker
Convergence			Convergence Pharmaceuticals Ltd.
CRL			Complete Response Letter
CROs			Contract Research Organizations
CTAD			Clinical Trials on Alzheimer's Disease
Dayra			Dayra Therapeutics, Inc.
Denali			Denali Therapeutics Inc.
Directors Plan			Biogen Inc. 2015 Non-Employee Directors Equity Plan
District Court			U.S. District Court for the District of Massachusetts
DOJ			U.S. Department of Justice
DPN			Diabetic Painful Neuropathy
EC			European Commission
EHS			Environment, Health and Safety
Eisai			Eisai Co., Ltd.
EMA			European Medicines Agency
EPO			European Patent Office
ERG			Employee Resource Group
ERM			Enterprise Risk Management
E.U.			European Union
FA			Friedreich Ataxia
FASB			Financial Accounting Standards Board
FCPA			Foreign Corrupt Practices Act
FDA			U.S. Food and Drug Administration

DEFINED TERMS (continued)

Fit for Growth			Cost saving program initiated in 2023
FSS			Federal Supply Schedule
GCP			Good Clinical Practices
GDPR			General Data Protection Regulation
Genentech			Genentech, Inc.
GILTI			Global Intangible Low-Taxed Income
GloBE			Global Anti-Base Erosion
GMP			Good Manufacturing Practices
HHS			U.S. Department of Health and Human Services
HI-Bio			Human Immunology Biosciences, Inc.
Humana			Humana Inc.
IgAN			Immunoglobulin A Nephropathy
IND			Investigational New Drug
Ionis			Ionis Pharmaceuticals Inc.
IPR&D			In-process Research and Development
IRA			Inflation Reduction Act of 2022
IT			Information Technology
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
LTI			Long-term Incentive
MAA			Marketing Authorization Application
MFN			Most-Favored-Nation
MHRA			Medicines and Healthcare products Regulatory Agency
MorphoSys			MorphoSys AG
MS			Multiple Sclerosis
MVI			Microvascular Inflammation in Kidney Transplant Patients
NDA			New Drug Application
NDS			New Drug Submission
Neurimmune			Neurimmune SubOne AG
NIST			National Institute of Standards and Technology
NMPA			National Medical Products Administration
OBBBA			One Big Beautiful Bill Act
ODD			Orphan Drug Designation
OECD			Organization for Economic Co-operation and Development
OIE			Other (Income) Expense, Net
Organon			Organon LLC
PDUFA			Prescription Drug User Fee Act
PFAS			Per- and Polyfluoroalkyl Substances
PHS			Public Health Service
PMN			Primary Membranous Nephropathy
Polpharma			Polpharma Biologics S.A.
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.
REMS			Risk Evaluation and Mitigation Strategies
RMS			Relapsing MS
RNAi			RNA Interference

DEFINED TERMS (continued)

RRMS			Relapsing-Remitting MS
RTP			Research Triangle Park, North Carolina
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
SMN			Survival Motor Neuron
SOD1			Superoxide Dismutase 1
SPC			Supplementary Protection Certificate
SSP			Supplemental Savings Plan
Supernus			Supernus Pharmaceuticals, Inc.
SWISSMEDIC			Swiss Agency for Therapeutic Products
TNF			Anti-tumor Necrosis Factor
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			U.S. Department of Veterans Affairs
Vanqua			Vanqua Bio, Inc.
VAT			Value-added Tax

PART I