What changed in this filing

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Item 1. Business

2026-02-06 compared with 2025-02-12 · 335 added, 367 removed, 838 unchanged (46% of the section changed)

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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.

for the treatment of FA in adults and adolescents aged 16 years and older.

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;

Our marketed products include VUMERITY, TYSABRI, TECFIDERA, AVONEX and PLEGRIDY for the treatment of MS;

SPINRAZA for the treatment of SMA;

SKYCLARYS for the treatment of FA;

QALSODY for the treatment of ALS;

and FUMADERM for the treatment of severe plaque psoriasis.

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.

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 Supernus 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;

GAZYVA for the treatment of CLL, follicular lymphoma and, following its approval in October 2025, lupus nephritis;

OCREVUS for the treatment of PPMS and RMS;

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IMRALDI, an adalimumab biosimilar referencing HUMIRA;

FLIXABI, an infliximab biosimilar referencing REMICADE;

and BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS, in certain international markets, as well as TOFIDENCE, a tocilizumab biosimilar referencing ACTEMRA, in the U.S.

and certain international markets.

We also have commercialization rights related to OPUVIZ, an aflibercept biosimilar referencing EYLEA.

On July 2, 2024, we completed the acquisition of HI-Bio.

As a result of this transaction we acquired HI-Bio's lead asset, felzartamab, an anti-CD38 antibody currently being evaluated for three leading indications, AMR, PMN and IgAN.

For additional information on our acquisition of HI-Bio, please read Note 2, Acquisitions , to our consolidated financial statements included in this report.

and FLIXABI, an infliximab biosimilar referencing REMICADE.

For additional information on our collaboration arrangements, please read Note 19, Collaborative and Other Relationships , to our consolidated financial statements included in this report.

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KEY BUSINESS DEVELOPMENTS

The following is a summary of key developments affecting our business since the beginning of 2025.

ACQUISITIONS AND DIVESTITURES

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 potential future development and regulatory milestone payments.

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.

For additional information on our acquisition of HI-Bio, please read Note 2, Acquisitions , to our consolidated financial statements included in this report.

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 consolidated statements of income for the year ended December 31, 2024.

For additional information on the sale of our PRV, please read Note 3, Dispositions , to our consolidated financial statements included in this report.

ALCYONE THERAPEUTICS, INC.

In November 2025 we completed the acquisition of all of the issued and outstanding shares of Alcyone Therapeutics, Inc., a clinical-stage biotechnology company focused on pediatric care through precision CNS therapeutics and dosing platforms.

Alcyone's lead asset is ThecaFlex DRx, an implantable subcutaneous port and catheter device being investigated for the intrathecal delivery of ASOs, including SPINRAZA, which is designed to provide an alternative to repeat lumbar punctures in chronic intrathecal administration of medicines.

Total consideration for this transaction, which was recorded in acquired in-process research and development, upfront and milestone expense in our consolidated statements of income for the year ended December 31, 2025, was approximately $85.0 million, comprising a $50.0 million payment made upon closing and a $35.0 million payment that was considered probable as of December 31, 2025, and made upon FDA approval of a supplemental application in January 2026.

We may pay additional development and regulatory milestone payments to the former shareholders of Alcyone of up to a total of $75.0 million if approval is received for ThecaFlex DRx administration of SPINRAZA or other additional pipeline products.

We accounted for this transaction as an asset acquisition as the value being acquired primarily relates to a single asset.

U nder the terms of this acquisition, we will oversee the end-to-end development, manufacturing and commercialization of ThecaFlex DRx .

For additional information on our acquisition of Alcyone, please read Note 2, Acquisitions, to our consolidated financial statements included in this report.

COLLABORATIVE AND OTHER RELATIONSHIPS

DAYRA THERAPEUTICS, INC.

COLLABORATION

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.

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.

For additional information on our research arrangement with Dayra, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

VANQUA BIO, INC.

COLLABORATION

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.

For additional information on our license agreement with Vanqua, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

CITY THERAPEUTICS, INC.

COLLABORATION

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.

For additional information on our strategic research arrangement with City Therapeutics, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

STOKE THERAPEUTICS, INC.

COLLABORATION

In February 2025 we entered into a collaboration and license agreement with Stoke to co-develop and commercialize zorevunersen, an investigational ASO that targets the SCN1A gene for the potential treatment of Dravet syndrome, a rare form of genetic epilepsy associated with refractory seizures and neurodevelopmental impairments.

Zorevunersen dosed its first patient in August 2025, advancing zorevunersen to a global Phase 3 trial.

Under the terms of this agreement, Stoke will continue to lead global development and retain exclusive development and commercialization rights for zorevunersen in the U.S., Canada and Mexico and we will have exclusive rights to commercialize zorevunersen in the rest of the world.

In connection with the closing of this transaction we made an upfront payment of $165.0 million to Stoke, 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 also have an exclusive option to license certain future follow-on ASO products targeting the SCN1A gene in all territories worldwide other than the U.S., Canada and Mexico, in exchange for separate milestone, cost sharing and royalty considerations.

For additional information on our collaboration arrangement with Stoke, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

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 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.

For additional information on our funding arrangement with Royalty Pharma, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

DEVELOPMENTS IN KEY COLLABORATIVE RELATIONSHIPS

For additional information on our collaborative and other relationships discussed below, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

LEQEMBI (lecanemab)

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consisted of the following:

• In January 2026 the FDA accepted for review the supplemental BLA for LEQEMBI subcutaneous autoinjector, LEQEMBI IQLIK, for weekly starting dose, with a PDUFA action date of May 24, 2026.

• In August 2025 the FDA approved the BLA for LEQEMBI subcutaneous autoinjector, LEQEMBI IQLIK, for weekly maintenance dosing.

• In January 2025 the FDA approved LEQEMBI monthly IV maintenance dosing for the treatment of early Alzheimer's disease.

• In January 2025 the FDA accepted for review the BLA for LEQEMBI subcutaneous autoinjector for weekly maintenance dosing, with a PDUFA action date set for August 31, 2025.

• In July 2024 Eisai presented new clinical data from the CLARITY AD study open-label extension of LEQEMBI, demonstrating that three years of continuous LEQEMBI treatment reduced clinical decline, resulting in a clinically meaningful benefit for early Alzheimer's disease patients.

Rest of World

Key developments related to LEQEMBI (lecanemab) in rest of world markets consisted of the following:

• In January 2025 we and Eisai announced an update regarding the ongoing regulatory review of the MAA for lecanemab in the E.U., which the CHMP of the EMA previously adopted a positive opinion on in November 2024.

The EC has asked the CHMP to consider information on the safety of lecanemab that became available after the adoption of the CHMP opinion in November 2024 and whether this may require an update of the opinion, and to consider whether the wording of the risk minimization measures in the opinion is clear enough to ensure correct implementation.

These will be discussed at the CHMP meeting in February 2025.

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• In December 2024 LEQEMBI was approved by the Federal Commission for the Protection Against Sanitary Risk in Mexico.

• In November 2024 we and Eisai announced the launch of LEQEMBI in South Korea, which had been approved by the Ministry of Food and Drug Safety in South Korea in May 2024.

• In October 2024 the Therapeutic Goods Administration of Australia issued a public statement about the initial decision not to register lecanemab.

In December 2024 Eisai submitted a request for reconsideration of this decision.

• In August 2024 LEQEMBI was approved by the Medicines and Healthcare products Regulatory Agency in Great Britain and by the Ministry of Health and Prevention in the United Arab Emirates.

• In July 2024 LEQEMBI was approved in Hong Kong and Israel.

• In June 2024 we and Eisai announced the launch of LEQEMBI in China, which had been approved by the NMPA in China in January 2024.

UCB COLLABORATION

In September 2024 we and UCB announced positive topline data from the Phase 3 PHOENYCS GO study of dapirolizumab pegol, a novel Fc-free anti-CD40L drug candidate, in people living with moderate-to-severe SLE.

The Phase 3 study met the primary endpoint demonstrating clinical improvement in moderate-to-severe SLE with clinical improvements observed among key secondary endpoints.

Based on these results, UCB and Biogen initiated a second Phase 3 study in late 2024.

• In January 2026 the BLA for LEQEMBI subcutaneous autoinjector was accepted for review by the NMPA in China.

• In November 2025 Eisai filed an NDA for LEQEMBI in Japan seeking approval for a subcutaneous autoinjector as a new route of administration to Japan's Pharmaceuticals and Medical Devices Agency.

• In November 2025 the MHRA in the UK approved LEQEMBI monthly IV maintenance dosing for the treatment of early Alzheimer's disease.

• In October 2025 Health Canada issued a Notice of Compliance with Conditions for LEQEMBI for the treatment of adult patients with a clinical diagnosis of mild cognitive impairment or mild dementia due to Alzheimer's disease who are either apolipoprotein E ε4 non-carriers or heterozygotes and who have confirmed amyloid pathology.

• In September 2025 the National Medical Products Administration in China approved LEQEMBI monthly IV maintenance dosing for the treatment of early Alzheimer's disease.

• In September 2025 the Therapeutic Goods Administration of Australia approved LEQEMBI for adults who are either apolipoprotein E ε4 non-carriers or heterozygous carriers.

• 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.

• In April 2025 the EC approved LEQEMBI in the E.U.

for the treatment of adult patients with a clinical diagnosis of mild cognitive impairment and mild dementia due to Alzheimer's disease who are apolipoprotein E ε4 non-carriers or heterozygotes with confirmed amyloid pathology.

ZURZUVAE (zuranolone)

• In September 2025 the EC approved ZURZUVAE in the E.U.

for the treatment of PPD in adults following childbirth, offering the first and only treatment indicated for PPD in the E.U.

• In August 2025 the Medicines and Healthcare products Regulatory Agency in the U.K.

granted marketing authorization for ZURZUVAE for moderate to severe PPD in the U.K.

OTHER KEY DEVELOPMENTS

• In June 2025 we announced the initiation of dosing in the global Phase 3 PREVAIL study.

This study will evaluate the efficacy and safety of the investigational drug felzartamab compared to placebo on proteinuria and preservation of kidney function in adults diagnosed with IgAN.

In connection with the initiation of this dosing we paid a $30.0 million milestone payment to MorphoSys in July 2025.

Additionally, in June 2025 we announced the initiation of dosing in the global Phase 3 PROMINENT study.

This study will evaluate the efficacy and safety of the investigational drug felzartamab compared to tacrolimus in adults diagnosed with PMN.

• In March 2025 we announced the initiation of dosing in the global Phase 3 TRANSCEND study.

This study will evaluate the efficacy and safety of the investigational drug felzartamab compared to placebo in adult kidney transplant recipients diagnosed with AMR.

In connection with the initiation of this dosing we paid a $35.0 million milestone payment to MorphoSys in April 2025.

SPINRAZA (nusinersen)

• In January 2026 the EC granted marketing authorization for a high dose regimen of SPINRAZA in the E.U.

for the treatment of 5q SMA, which is the most common form of the disease and represents approximately 95% of all SMA cases.

The high dose regimen is comprised of 50 mg/5 mL and 28 mg/5 mL doses and individuals transitioning from the 12 mg dose will receive one 50 mg dose in place of their next 12 mg dose, followed by 28 mg maintenance doses every four months thereafter.

• In September 2025 the high dose regimen of SPINRAZA was approved by the Ministry of Health, Labour and Welfare in Japan.

• In September 2025 the FDA issued a CRL for the supplemental NDA for a higher dose regimen of nusinersen for the treatment of SMA.

The CRL requested an update to the technical information to be included in the Chemistry Manufacturing and Controls module of the supplemental NDA and did not cite any deficiencies in the clinical data of the high dose regimen.

We resubmitted the supplemental NDA to the FDA, which has been accepted for review with a PDUFA action date of April 3, 2026.

SKYCLARYS (omaveloxolone)

• In April 2025 SKYCLARYS was approved by the Medicines and Healthcare products Regulatory Agency in the U.K.

and in Brazil.

In March 2025 SKYCLARYS was approved by Health Canada.

QALSODY (tofersen)

• In July 2025 the Medicines and Healthcare products Regulatory Agency in the U.K.

approved QALSODY for the treatment of ALS in adults who have a mutation in the SOD1 gene.

• In March 2025 Health Canada issued marketing authorization with conditions for QALSODY for the treatment of ALS in adults who have a mutation in the SOD1 gene.

The authorization is conditional, pending the results of trials to verify its clinical benefit.

• In April 2025 the FDA granted Fast Track designation to BIIB080, an investigational ASO therapy targeting tau for the potential treatment of Alzheimer's disease.

CORPORATE MATTERS

2025 SENIOR NOTES

On May 12, 2025, we issued senior unsecured 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 our 4.050% Senior Notes due September 15, 2025, prior to maturity.

For additional information relating to our 2025 Senior Notes, please read Note 13, Indebtedness , to our consolidated financial statements included in this report.

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% of 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.

For additional information on our lease agreement, please read Note 12, Leases, to our consolidated financial statements included in this report.

MANAGEMENT CHANGES

• In October 2024 we announced that Michael R.

McDonnell, Executive Vice President and Chief Financial Officer, plans to retire from Biogen on March 1, 2025.

McDonnell's retirement, Robin C.

Kramer, currently Senior Vice President and Chief Accounting Officer at Biogen, will assume the role of Executive Vice President and Chief Financial Officer.

• In January 2025 we announced the appointment of Sean Godbout as Vice President, Chief Accounting Officer and Global Corporate Controller, effective March 1, 2025, upon the transition of Robin C.

Kramer, currently Senior Vice President and Chief Accounting Officer at Biogen, to the role of Executive Vice President and Chief Financial Officer.

BOARD OF DIRECTORS UPDATE

• Effective October 1, 2024, Lloyd B.

joined our Board of Directors.

• Effective January 1, 2025, Sir Menelas (Mene) Pangalos, Ph.D.

joined our Board of Directors.

• In March 2025 Robin C.

Kramer became Executive Vice President and Chief Financial Officer.

• In March 2025 Sean Godbout became Vice President, Chief Accounting Officer and Global Corporate Controller.

For additional information on our executive officers, please read the subsection entitled "Information about our Executive Officers" included in this report.

PRODUCT AND PIPELINE DEVELOPMENTS

ALZHEIMER'S DISEASE

LEQEMBI (lecanemab )

• In October 2024 Eisai presented data on benefits of long-term administration of dual-acting LEQEMBI at the 2024 CTAD conference.

The data presented additional measures resulting from the three years of continuous LEQEMBI treatment, showing that 46% of patients improved or had no decline and 33% showed improvement from baseline on the CDR-SB.

On the ADAS-Cog14 measurement scale, 46% of patients showed improvement or no decline and 43% showed improvement.

On the ADCS MCI-ADL measurement scale, 51% of patients showed improvement or no decline and 48% showed improvement.

• In July 2024 Eisai announced the results of a detailed analysis of the Phase 3 CLARITY Alzheimer's disease study of LEQEMBI at the 2024 AAIC conference.

The study provided further Phase 3 analysis showing three years of continuous LEQEMBI treatment reduced clinical decline by -0.95 on CDR-SB showing continued clinically and personally meaningful benefit for early Alzheimer's disease patients.

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• Felzartamab was granted ODD in the E.U.

in IgAN and solid organ transplantation in November 2024 and December 2024, respectively.

• In October 2024 we presented complete results from the Phase 2 IGNAZ study evaluating felzartamab, an investigational anti-CD38 monoclonal antibody, in people living with IgAN during the American Society of Nephrology Kidney Week 2024.

The results from the study showed substantial reductions in proteinuria, stabilization of kidney function and sustained treatment effect more than 18 months after the last dose of felzartamab.

• In October 2024 the FDA granted felzartamab Breakthrough Therapy Designation for the treatment of late AMR without T-cell mediated rejection in kidney transplant patients.

• In December 2025 we and Eisai announced that LEQEMBI has been included in the "Commercial Insurance Innovative Drug List" recently introduced by the National Healthcare Security Administration of China.

The Commercial Insurance Innovative Drug List is based on new policies of the Chinese government to support the development and access of innovative medicines.

• In December 2025 Eisai presented Phase 3 clinical data confirming pharmacological effect of LEQEMBI at the 2025 CTAD conference.

The findings represent the results from a large-scale clinical study demonstrating, for the first time, that binding of lecanemab to protofibrils can be measured in cerebrospinal fluid, enabling further understanding of how lecanemab slows Alzheimer's disease progression.

• In July 2025 Eisai announced the interim results of a two-year real-world study of LEQEMBI in the U.S.

at the 2025 AAIC conference.

The study was conducted to investigate the actual state of real-world clinical treatment with LEQEMBI at 15 medical centers in the U.S., with a final report scheduled for late in the third quarter of Eisai's fiscal year ending March 31, 2026.

In this interim study, 83.6% of patients either remained at the same clinical stage or improved from mild dementia to MCI (stable:

76.9%, improvement:

Additionally, at time of interim data cut, 86.7% of patients who had received 40 or more doses over 18 months remained stable or showed clinical improvement (stable:

66.7%, improvement:

• In December 2025 we and Stoke announced new data that further support the potential of zorevunersen, an investigational ASO, as a disease-modifying medicine for Dravet syndrome, at the 2025 American Epilepsy Society Annual Meeting in Atlanta, Georgia.

Long-term results from the ongoing Phase 1/2a and OLE studies demonstrated durable seizure reductions, including increases in seizure-free days, in addition to improvements in cognition, behavior and quality of life in patients treated with zorevunersen on top of care anti-seizure medicines.

• In November 2025 we and Stoke announced the publication of final data from the BUTTERFLY study, a prospective, two-year natural history study in people with Dravet syndrome, a severe developmental and epileptic encephalopathy characterized by recurrent seizures and significant and behavioral impairments.

The BUTTERFLY study evaluated the impact of Dravet syndrome on adaptive functioning and neurodevelopment over two years in children and adolescents ages 2 to 18 years old.

Results showed neurodevelopment plateaued at the developmental age of approximately two years old.

Over the two-year study, patients experienced minimal changes in cognitive and behavior, including communication, motor skills and personal skills, compared to typical neurodevelopment expected for children of the same age, and major motor seizure frequency increased by 10.6% over two years.

• In September 2025 we and Stoke announced data from Phase 1/2a and open-label extension studies of zorevunersen that support the potential for zorevunersen to be the first disease-modifying medicine for Dravet syndrome at the 36th International Epilepsy Congress in Lisbon, Portugal.

The study showed durable reductions in seizures and continuing improvements in cognition and behavior through three years in patients who continued to receive zorevunersen in the OLE studies.

The study also showed substantial increase in seizure-free days and continuous improvement in quality of life demonstrated in patients already taking standard of care anti-seizure medicines.

• In August 2025 we and Stoke announced the first patient dosed in the Phase 3 EMPEROR study of zorevunersen, a potential disease-modifying treatment for Dravet syndrome.

• In July 2025 we and Stoke announced the presentation of data from an analysis that informed the design of the Phase 3 EMPEROR study and evaluated the potential effects of the Phase 3 zorevunersen dosing regimen.

The data are complementary to previously reported data from a broader cohort of patients treated with zorevunersen in the Phase 1/2a and OLE studies that showed improvements within the first 9 months and continuing improvements through an additional two years.

SPINRAZA (nusinersen)

• In January 2025 the FDA accepted the supplemental NDA and the EMA validated the application for a higher dose regimen of nusinersen for SMA.

The higher dose regimen of nusinersen comprises a more rapid loading regimen, two 50 mg-doses 14 days apart, and higher maintenance regimen, 28 mg, every four months, compared to the currently approved dose of SPINRAZA.

• In September 2024 we announced positive topline data from the Phase 2/3 DEVOTE study of nusinersen, which evaluated the safety and efficacy of a higher dose regimen of nusinersen in treatment-naive symptomatic infants with SMA.

• In March 2024 we announced new data from the Phase 4 RESPOND study for SPINRAZA.

The study showed that neurofilament levels, an indicator of neurodegeneration, were reduced in nearly all study participants treated with SPINRAZA.

The reductions in biomarker complement previously reported RESPOND study efficacy results showing improved motor function in most participants treated with SPINRAZA after gene therapy.

• In September 2024 SKYCLARYS was approved by SWISSMEDIC for the treatment of FA in adults and adolescents aged 16 years and older.

• In July 2024 the first pediatric patient was treated in the Phase 1 study of SKYCLARYS designed to identify the appropriate dose for the pediatric population living with FA.

• In December 2024 the Japanese Ministry of Health, Labor and Welfare approved QALSODY in Japan.

• In October 2024 QALSODY was approved in China by the NMPA under the conditional approval pathway for the treatment of adults with ALS associated with a mutation in the SOD1 gene.

• In May 2024 the EC approved QALSODY in the E.U.

for the treatment of adults with ALS associated with a mutation in the SOD1 gene.

QALSODY is the first treatment approved in the E.U.

to target a genetic cause of ALS.

• In June 2025 we announced new data that reinforce the clinical impact of nusinersen across a broad spectrum of individuals affected by SMA.

These latest findings from Part C of the DEVOTE trial evaluating a higher dose regimen of nusinersen and the NURTURE trial which evaluated the approved 12 mg regimen of SPINRAZA in clinically presymptomatic SMA was presented at the SMA Research & Clinical Care Meeting hosted by Cure SMA.

The study showed improvements observed with higher dose regimen of nusinersen in previously treated patient population.

SALANERSEN (BIIB115)

• In June 2025 we announced positive interim topline results from the Phase 1b study of salanersen, an ASO being developed for the treatment of SMA.

Interim Phase 1b data shows children with SMA previously treated with gene therapy experienced a substantial slowing of neurodegeneration and clinically meaningful improvements in motor function following initiation of salanersen.

Our Phase 3 registrational study of salanersen is expected to begin in 2026.

SKYCLARYS (OMAVELOXOLONE)

• In June 2025 we announced the initiation of dosing in the global Phase 3 BRAVE study of omaveloxolone in children with FA between the ages of two to sixteen.

The BRAVE study will evaluate the efficacy, safety, pharmacokinetics and pharmacodynamics of omaveloxolone in approximately 255 children living with FA.

• In December 2025 the Journal of the American Medical Association Neurology published final results from the completed Phase 3 VALOR study and its OLE study evaluating QALSODY for the treatment of SOD1 ALS with over 3.5 years of follow-up.

These results show that early initiation of QALSODY was associated with numerically slower decline in measures of clinical function, breathing and strength, as well as reduction in the risk of death or permanent ventilation.

Sustained reductions in neurofilament, a marker of neurodegeneration, further validate the clinical results and demonstrate QALSODY's impact on the underlying biology of SOD1 ALS.

DISCONTINUED PROGRAMS AND STUDIES

SAGE COLLABORATION

In October 2024 we and Sage agreed to not pursue further development of zuranolone for the potential treatment of MDD.

This decision was based on the significant new investment and time we expect would be needed to conduct the additional studies required to support approval of this indication.

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In July 2024 we and Sage announced that the Phase 2 KINETIC 2 dose-range study of BIIB124 did not meet its endpoints.

Based on these results, we discontinued our further development of BIIB124 and terminated our rights under the collaboration and license agreement specific to BIIB124, effective February 17, 2025.

SAMSUNG BIOEPIS 2019 DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

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.

Biogen will transfer commercialization rights for BYOOVIZ and OPUVIZ in the U.S.

and Canada back to Samsung Bioepis over a period of up to 18 months.

During this transition period, we will continue to commercialize BYOOVIZ.

The termination does not impact the other markets in the DCA Agreement.

IONIS COLLABORATION

In May 2024 we and Ionis announced that the Phase 1/2 ALSpire study of BIIB105, an investigational ASO for the potential treatment of ALS, did not meet its endpoints.

Based on these results, we discontinued our further development of BIIB105.

In May 2024 we announced that we have elected not to exercise our option to license and lead development of BIIB121, an ASO for the potential treatment of Angelman syndrome.

MERZ THERAPEUTICS (PREVIOUSLY ACORDA THERAPEUTICS, INC.)

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.

We are now working with Merz Therapeutics on the transition of global commercialization rights of FAMPYRA and we expect to recognize minimal revenue in 2025.

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 a nd recognized a de minimis loss within our consolidated statements of income for the year ended December 31, 2025.

For additional information on our sale of TOFIDENCE, please read Note 3, Dispositions , to our consolidated financial statements included in this report.

SALE OF BYOOVIZ AND OPUVIZ RIGHTS

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.

BIIB143 (cemdomespib)

In early 2025 we discontinued further development of BIIB143 (cemdomespib) for the treatment of diabetic neuropathic pain, as part of our ongoing pipeline prioritization efforts.

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In early 2025 we discontinued further development of BIIB143 (cemdomespib) for the treatment of DPN, as part of our ongoing pipeline prioritization efforts.

FELZARTAMAB - LUPUS NEPHRITIS

In November 2025 we discontinued the open label Phase 1b study of felzartamab for the treatment of lupus nephritis.

MARKETED PRODUCTS

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(1) MS includes TECFIDERA, VUMERITY, AVONEX, PLEGRIDY, TYSABRI and FAMPYRA.

(2) Rare disease includes SPINRAZA, QALSODY, which became commercially available in the U.S.

during the second quarter of 2023 and commercially available in the E.U.

during the second quarter of 2024, and SKYCLARYS, which was obtained as part of our acquisition of Reata in September 2023.

SKYCLARYS became commercially available in the U.S.

during the second quarter of 2023 and we began recognizing revenue from SKYCLARYS in the U.S.

during the fourth quarter of 2023, subsequent to our acquisition.

SKYCLARYS was approved and became commercially available in the E.U.

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

(2) Rare disease includes SPINRAZA, QALSODY, which became commercially available in the E.U.

during the second quarter of 2024, and SKYCLARYS which became commercially available in the E.U.

during the first quarter of 2024.

(3) Biosimilars includes BENEPALI, IMRALDI, FLIXABI, BYOOVIZ, which became commercially available in certain international markets in 2023, and TOFIDENCE, which became commercially available in the U.S.

during the second quarter of 2024.

(3) Biosimilars includes BENEPALI, IMRALDI, FLIXABI, BYOOVIZ and TOFIDENCE.

In 2025 we completed the sale of our rights to TOFIDENCE and BYOOVIZ.

For additional information on our arrangements with Samsung Bioepis, please read Note 19, Collaborative and Other Relationships , to our consolidated financial statements included in this report.

(4) Alzheimer's collaboration revenue consists of our 50.0% share of LEQEMBI product revenue, net and cost of sales, including royalties.

(5) Anti-CD20 therapeutic programs include RITUXAN, RITUXAN HYCELA, GAZYVA, OCREVUS and LUNSUMIO, which became commercially available in the U.S.

during the first quarter of 2023.

(6) Other includes FUMADERM, ADUHELM and ZURZUVAE, which became commercially available in the U.S.

during the fourth quarter of 2023.

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Product sales for TECFIDERA, TYSABRI and SPINRAZA each accounted for more than 10.0% of our total revenue for the years ended December 31, 2024, 2023 and 2022.

(5) Anti-CD20 therapeutic programs include RITUXAN, RITUXAN HYCELA, GAZYVA, OCREVUS and LUNSUMIO.

(6) Other includes FUMADERM, ADUHELM and ZURZUVAE.

Product sales for TYSABRI and SPINRAZA each accounted for more than 10.0% of our total revenue for the years ended December 31, 2025, 2024 and 2023.

For additional financial information about our product and other revenue and geographic areas where we operate, please read Note 5, Revenue and Note 25, Segment Information, to our consolidated financial statements included in this report and Item 7.

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RRMS in the E.U.

Alkermes Pharma Ireland Limited, a subsidiary of Alkermes U.S.

RMS None U.S.

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RRMS in the E.U.

For additional information on our collaboration arrangements with Alkermes, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

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ALZHEIMER'S DISEASE

Alzheimer's disease includes LEQEMBI for the treatment of early Alzheimer's disease.

Alzheimer's disease, the most common form of dementia, is a progressive neurological illness that causes a gradual decline in cognitive abilities, usually during a span of seven to ten years.

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Alzheimer's disease Eisai U.S.

Great Britain

United Arab Emirates

For additional information on our collaboration arrangements with Eisai, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

NEUROPSYCHIATRY

Neuropsychiatry includes ZURZUVAE for PPD, which became commercially available in the U.S.

during the fourth quarter of 2023.

Neuropsychiatry includes ZURZUVAE for PPD.

PPD symptoms are estimated to affect approximately one in eight women who have given birth in the U.S.

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Product Indication Collaborator Major Markets

PPD in adults Sage U.S.

For additional information on our collaboration arrangements with Sage, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

Rare disease includes SPINRAZA for SMA, QALSODY for ALS, which became commercially available in the U.S.

during the second quarter of 2023 and commercially available in the E.U.

during the second quarter of 2024, and SKYCLARYS for FA, which was obtained as part of our acquisition of Reata in September 2023.

SKYCLARYS became commercially available in the U.S.

during the second quarter of 2023 and we began recognizing revenue from SKYCLARYS in the U.S.

during the fourth quarter of 2023, subsequent to our acquisition.

SKYCLARYS was approved and became commercially available in the E.U.

PPD in adults Supernus U.S.

For additional information on our collaboration arrangements with Supernus, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

Rare disease includes SPINRAZA for SMA, QALSODY for ALS, which became commercially available in the E.U.

during the second quarter of 2024, and SKYCLARYS for FA, which became commercially available in the E.U.

during the first quarter of 2024.

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People with Type 2 and Type 3 SMA produce greater amounts of SMN protein and have less severe, but still life-altering, forms of SMA.

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FA is an inherited, debilitating and degenerative neuromuscular disorder that is typically diagnosed during adolescence and can ultimately lead to premature death.

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For additional information on our collaboration arrangements with Ionis, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

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Biosimilars are a group of biologic medicines that are highly similar to currently available biologic therapies developed by companies known as "originators".

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IMRALDI, an adalimumab biosimilar referencing HUMIRA;

FLIXABI, an infliximab biosimilar referencing REMICADE;

and BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS, in certain international markets, as well as TOFIDENCE, a tocilizumab biosimilar referencing ACTEMRA, which became commercially available in the U.S.

during the second quarter of 2024 and approved in the E.U.

during the second quarter of 2024.

We also have commercialization rights related to OPUVIZ, an aflibercept biosimilar referencing EYLEA, which was approved in the E.U.

during the fourth quarter of 2024.

and FLIXABI, an infliximab biosimilar referencing REMICADE.

Our current biosimilar products and major markets are as follows:

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Psoriatic arthritis

Psoriasis Samsung Bioepis France

Neovascular (wet) age-related macular degeneration

Macular edema following retinal vein occlusion

Myopic choroidal neovascularization Samsung Bioepis France

Rheumatoid arthritis

Polyarticular juvenile idiopathic arthritis

Systemic juvenile idiopathic arthritis

Giant cell arteritis

COVID-19 Bio-Thera Solutions, Ltd.

Psoriasis Samsung Bioepis Austria

For additional information on our collaboration arrangements with Samsung Bioepis, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

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GENENTECH RELATIONSHIPS

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follicular lymphoma

In combination with chemotherapy followed by GAZYVA alone for previously untreated follicular lymphoma U.S.

In combination with chemotherapy followed by GAZYVA alone for previously untreated follicular lymphoma

For the treatment of adult patients with active lupus nephritis who are receiving standard therapy U.S.

Relapsed or refractory follicular lymphoma U.S.

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For additional information on our collaboration arrangements with Genentech, please read Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

Product Indication Collaborator Major Markets

Moderate to severe plaque psoriasis None

PATIENT SUPPORT AND ACCESS

We interact with patients, advocacy organizations and healthcare societies in order to gain insights into unmet needs.

The insights gained from these engagements help us support patients with services, programs and applications that are designed to help patients lead fuller, healthier lives.

The insights gained from these engagements help us support patients with services, programs and applications that are designed to help transform patients' lives.

Among other things, we provide customer service and other related programs for our products, such as disease and product specific websites, insurance research services, financial assistance programs and the facilitation of the procurement of our marketed products.

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We are dedicated to helping patients obtain access to our therapies.

Our patient support representatives have access to a suite of financial assistance tools.

Our patient support representatives have access to a comprehensive suite of financial assistance tools.

With those tools, we help patients understand their insurance coverage and, if needed, help patients compare insurance options and programs.

In the U.S., we have established programs that provide co-pay assistance or free product for qualified uninsured or underinsured patients, based on specific eligibility criteria.

In the U.S., we have established programs that provide co-pay assistance for qualified commercially insured patients and free product for qualified uninsured or underinsured patients, based on specific eligibility criteria.

We believe all healthcare stakeholders have a shared responsibility to ensure patients have equitable access to new, innovative medicines.

We regularly review our pricing strategy and prioritize patient access to our therapies.

We have a value-based contracting program designed to align the price of our therapies to the value our therapies deliver to patients.

We have a value-based contracting program designed to align the price of our therapies to the value our therapies deliver

We also work with regulators, clinical researchers, ethicists, physicians and patient advocacy groups and communities, among others, to determine how best to address requests for access to our investigational therapies in ways that are consistent with our patient-focused values and compliant with regulatory standards and protocols.

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SALES FORCE AND MARKETING

We promote our marketed products worldwide, including in the U.S., Europe and Japan, primarily through our own sales forces and marketing groups.

We promote our marketed products worldwide, including in the U.S., Europe, Asia, the Middle East and Latin America, primarily through our own sales forces and marketing groups.

In some countries, particularly in areas where we continue to expand into new geographic areas, we partner with third parties.

RITUXAN, RITUXAN HYCELA, GAZYVA, OCREVUS, LUNSUMIO and COLUMVI are marketed by the Roche Group and its sublicensees.

We commercialize BENEPALI, IMRALDI, FLIXABI and BYOOVIZ pursuant to our agreement with Samsung Bioepis in certain international markets.

We focus our sales and marketing efforts on physicians in private practice or at major medical centers.

We commercialize BENEPALI, IMRALDI and FLIXABI pursuant to our agreement with Samsung Bioepis in certain international markets.

We focus our sales and marketing efforts on health care providers in private practice or at major medical centers.

We use customary industry practices to market our products and to educate physicians.

This includes our sales representatives calling on individual health care providers (in-person and virtually), advertisements, professional symposia, direct mail, digital marketing, point of care marketing, public relations and other methods.

We focus on health care provider sales and marketing efforts on providers in both private practice and at major medical centers.

DISTRIBUTION ARRANGEMENTS

We distribute our products in the U.S.

principally through wholesale and specialty distributors of pharmaceutical products and specialty pharmacies, mail order specialty distributors or shipping service providers.

principally through wholesale and specialty distributors of pharmaceutical products and specialty pharmacies.

In other countries, the distribution of our products varies from country to country, including through wholesale distributors of pharmaceutical products and third-party distribution partners who are responsible for most marketing and distribution activities.

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We distribute BENEPALI, IMRALDI and FLIXABI in certain countries in Europe and have an option to acquire exclusive rights to distribute these products in China.

We also distribute BYOOVIZ in certain international markets and TOFIDENCE in the U.S.

Our product sales to two wholesale distributors each accounted for more than 10.0% of our total revenue for the years ended December 31, 2025, 2024 and 2023, and on a combined basis, accounted for approximately 43.9%, 39.3% and 36.9%, respectively, of our gross product revenue.

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Patents are important for obtaining and protecting exclusive rights in our products and product candidates.

We regularly seek patent protection in the U.S., the E.U.

and Japan and in selected other countries for inventions originating from our research and development efforts and those we license or acquire.

We regularly seek patent protection in the U.S., the E.U., Asia, the Middle East and Latin America for inventions originating from our research and development efforts and those we license or acquire.

In addition, we license rights to various patents and patent applications.

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however, U.S.

patents on applications filed before June 8, 1995, may be effective until

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17 years from the issue date, if that is later than the 20-year date.

patents on applications filed before June 8, 1995, may be effective until 17 years from the issue date, if that is later than the 20-year date.

In some cases, the patent term may be extended to recapture a portion of the term lost during regulatory review of the claimed therapeutic or, in the case of the U.S., additional patent term may be awarded due to U.S.

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Regulatory exclusivity, which may consist of regulatory data protection and market protection, can also provide meaningful protection for our products.

Regulatory data protection provides to the holder of a drug or biologic marketing authorization, for a set period of time, the exclusive use of the proprietary pre-clinical and clinical data that it created at significant cost and submitted to the applicable regulatory authority to obtain approval of its product.

Regulatory data protection provides to the holder of a drug or biologic

marketing authorization, for a set period of time, the exclusive use of the proprietary preclinical and clinical data that it created at significant cost and submitted to the applicable regulatory authority to obtain approval of its product.

After the period of exclusive use, third parties are permitted to reference such data in abbreviated applications for approval and to market (subject to any applicable market protection) their generic drugs and biosimilars.

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and other territories covering various aspects of our products that may, if issued, extend exclusivity beyond the expiration of the patents listed in the table.

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Product Territory Patent No.

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Expiration (1)

TECFIDERA Europe 2,653,873 Methods of use 2028

PLEGRIDY U.S.

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7,838,657 SMA treatment via targeting of SMN2 splice site inhibitory sequences 2027

8,110,560 SMA treatment via targeting of SMN2 splice site inhibitory sequences 2025

8,361,977 Compositions and methods for modulation of SMN2 splicing 2030

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9,926,559 Compositions and methods for modulation of SMN2 splicing 2034

10,266,822 SMA treatment via targeting of SMN2 splice site inhibitory sequences 2025

10,436,802 Methods for Treating Spinal Muscular Atrophy 2035

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Europe 3,449,926 Compositions and methods for modulation of SMN2 splicing 2030 (6)

Europe 3,999,643 Methods of Treating or Preventing Spinal Muscular Atrophy 2040

8,025,878 Protofibril selective antibodies and the use thereof 2027 (1)(5)

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Europe 2,004,688 Improved protofibril selective antibodies and the use thereof 2027 (1)(9)

Product Territory Patent No.

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11,236,121 Crystalline 19-nor C3, 3-disubstituted C21-N-pyrazolyl steroid 2034 (5)

Europe 2,986,623 19-nor C3, 3-disubstituted c21-N-pyrazolyl steroids and methods of use thereof 2034

Europe 3,498,725 19-nor C3, 3-disubstituted C21-N-pyrazolyl steroid for use in therapy 2034

Europe 3,909,966 19-nor C3, 3-disubstituted C21-N-pyrazolyl steroid for use in therapy 2034

Europe 2,766,380 3.3 disubstituted 10-nore pregnane compounds, compositions and uses thereof 2032

SKYCLARYS U.S.

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11,091,430 Antioxidant Inflammation Modulators:

Oleanolic Acid Derivatives with Amino and other Modifications at C-17 (Treatment Method) 2029 (5)

Oleanolic Acid Derivatives with Amino and other Modifications at C-17 (Method of Use) 2029 (5)

11,919,838 Antioxidant Inflammation Modulators:

Oleanolic Acid Derivatives with Amino and other Modifications at C-17 (Method of Use) 2029 (5)

Europe 2,276,493 Antioxidant Inflammation Modulators:

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Europe 2,841,445 2,2-Difluoropropionamide Derivatives of Bardoxolone Methyl, Polymorphic Forms and Methods of Use Thereof (Composition) 2033 (7)

Europe 3,444,261 2,2-Difluoropropionamide Derivatives of Bardoxolone Methyl, Polymorphic Forms and Methods of Use Thereof (Composition) 2033

Europe 3,444,261 2,2-Difluoropropionamide Derivatives of Bardoxolone Methyl, Polymorphic Forms and Methods of Use Thereof (Method of Use) 2033

Footnotes follow on next page.

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(1) I n addition to patent protection, certain of our products are entitled to regulatory exclusivity in the U.S.

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ZURZUVAE U.S.

ZURZUVAE E.U.

SKYCLARYS U.S.

SKYCLARYS E.U.

(2) This patent is subject to granted SPCs in certain European countries, which extended the patent term in those countries to 2028.

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(8) This patent is subject to granted SPCs in certain European countries, which extended the patent term in those countries to 2039.

(9) SPC applications based on this patent have been filed in certain European countries, which if granted would extend the patent term in those countries to 2032.

The existence of patents does not guarantee our right to practice the patented technology or commercialize the patented product.

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Risk Factors included in this report, and the discussion of legal proceedings related to certain patents described above is set forth in Note 21, Litigation, to our consolidated financial statements included in this report.

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Competition in the biopharmaceutical industry and the markets in which we operate is intense.

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GENERIC AND BIOSIMILARS COMPETITION

Certain of our products already face, or may face in the future, competition from the introduction of generic versions, prodrugs and biosimilars of existing products and products approved under abbreviated regulatory pathways.

Certain of our products already face, or may face in the future, competition from the introduction of new originator therapies, generics, prodrugs and biosimilars of existing products and products approved under abbreviated regulatory pathways.

Such products are likely to be sold at substantially lower prices than branded products.

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Multiple TECFIDERA generic entrants are now in North America, Brazil and certain European countries and have deeply discounted prices compared to TECFIDERA.

We are defending the validity of our EP 2 653 873 patent related to TECFIDERA and expiring in 2028 in opposition proceedings in the European Patent Office.

We are also engaged in litigation in Europe to defend and enforce national counterparts of our EP 2 653 873 patent, with mixed results.

The generic competition for TECFIDERA has significantly reduced our TECFIDERA revenue and we expect that TECFIDERA revenue will continue to decline.

B i osimilar products referencing RITUXAN have launched in the U.S and are being offered at lower prices.

This competition has had a significant adverse impact on the pre-tax profits of our collaboration arrangements with Genentech, as the sales of RITUXAN have decreased substantially compared to prior periods.

We expect that biosimilar competition will continue to increase as these products capture additional market share and that this will have a significant adverse impact on our co-promotion profits in the U.S.

in future years.

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In November 2025 the Technical Boards of Appeal of the European Patent Office revoked our EP 2 653 873 patent related to TECFIDERA, after which we stopped enforcing this patent and its national counterparts.

B i osimilar products referencing RITUXAN are available in the U.S and are being offered at lower prices.

This competition has had a significant adverse impact on the pre-tax profits of our collaboration arrangements with

Genentech, as the sales of RITUXAN have decreased substantially compared to prior periods and we expect sales to continue to decrease.

A biosimilar entrant of TYSABRI was approved in the U.S.

We expect that future sales of TYSABRI may be adversely affected by the entrance of this biosimilar.

We expect that future sales of TYSABRI will continue to be adversely affected by the entrance of this biosimilar worldwide.

MULTIPLE SCLEROSIS

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Along with us, a number of companies are working to develop additional treatments for MS that may in the future compete with our MS products.

One competing product that was approved in the U.S.

in 2017 and in the E.U.

in 2018 is OCREVUS, a treatment for RMS and PPMS that was developed by Genentech.

Another competing product that was approved in the U.S.

in 2020 and the E.U.

in 2021 is KESIMPTA, a treatment for RMS that was developed by Novartis AG.

While we have a financial interest in OCREVUS, future sales of our MS products may be adversely affected if OCREVUS and KESIMPTA continue to gain market share, or if other MS products that we or our competitors are developing are commercialized.

Our MS products may be adversely affected if competitors continue to gain market share, or if other MS products that we or our competitors are developing are commercialized.

ALZHEIMER'S DISEASE

The market for the treatment of Alzheimer's disease is undeveloped and could be subject to rapid change in the future.

The market for the treatment of Alzheimer's disease is developing and could be subject to rapid change in the future.

Most current treatments are symptomatic or intended to improve quality of life.

Along with us, several companies are working to develop additional treatments.

We and our collaboration partner Eisai co-commercialize LEQEMBI, an anti-amyloid antibody for the treatment of Alzheimer's disease.

In 2024 a competing product, KISUNLA, a treatment for early symptomatic Alzheimer's disease that was developed by Eli Lilly and Company, was approved in the U.S.

Along with us, several companies are working to develop additional treatments.

A competing product, KISUNLA, a treatment for early symptomatic Alzheimer's disease that was developed by Eli Lilly and Company, was approved in the U.S.

in 2024 and in the E.U.

We are aware of other products now in development that, if approved, may also compete with LEQEMBI.

SPINAL MUSCULAR ATROPHY

We face competition from a gene therapy product ZOLGENSMA (onasemnogene abeparvovec-xioi) and an oral product EVRYSDI (risdiplam).

We expect that we will experience competition from both products in additional jurisdictions in the future, as well as from the launch of new formulations of those products, which may adversely affect our sales of SPINRAZA.

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We face competition from an oral product EVRYSDI (risdiplam) and a gene therapy product ZOLGENSMA (onasemnogene abeparvovec-xioi).

We expect that we will experience competition from both products in additional jurisdictions and new formulations of those products, which may adversely affect our sales of SPINRAZA.

RESEARCH AND DEVELOPMENT PROGRAMS

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Our research efforts are focused on better understanding the underlying biology of diseases so we can discover and deliver treatments that have the potential to make a real difference in the lives of patients with high unmet medical needs.

By applying our expertise in biologics and our capabilities in small molecule, antisense, gene therapy and other technologies, we target specific medical needs where we believe new or better treatments are needed.

By applying our expertise in biologics and our capabilities in small molecule, antisense and other technologies, we target specific medical needs where we believe new or better treatments are needed.

We intend to continue committing significant resources to targeted research and development opportunities where there is a significant unmet need and where a drug candidate has the potential to be highly differentiated.

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Risk Factors included in this report.

Alzheimer's Disease and

Dementia Lecanemab (Aβ mAb) (1)(2) - Early Alzheimer's

Lecanemab (Aβ mAb) (1) - Preclinical Alzheimer's

Lecanemab (Aβ mAb) (1) - Subcutaneous autoinjector maintenance - Early Alzheimer's

Regulatory Review

Lecanemab (Aβ mAb) (1) - Subcutaneous autoinjector initiation - Early Alzheimer's

Neurology Lecanemab (Aβ mAb) (1) - Preclinical Alzheimer's

BIIB080 (tau ASO) (1) - Alzheimer's

Neuropsychiatry Zuranolone (GABA A PAM) (1)(3) - PPD

Approved/Regulatory Review

Specialized Immunology Felzartamab (anti-CD38 mAb) - AMR Phase 2

Felzartamab (anti-CD38 mAb) - IgAN Phase 2

Felzartamab (anti-CD38 mAb) - PMN Phase 2

Felzartamab (anti-CD38 mAb) - lupus nephritis Phase 1

Izastobart (C5aR1 mAb) - complement mediated disease Phase 1

Dapirolizumab pegol (anti-CD40L) (1) - SLE

BIIB122 (LRRK2 inhibitor) (1) - Parkinson's

BIIB091 (peripheral BTK inhibitor) - MS Phase 2

Immunology Dapirolizumab pegol (anti-CD40L) (1) - SLE

Litifilimab (anti-BDCA2) - SLE Phase 3

Litifilimab (anti-BDCA2) - CLE Phase 3

Neuromuscular Disorders Omaveloxolone (Nrf2 activator) - FA (4)

BIIB142 (IRAK4 degrader) (1)

BIIB145 (BTK degrader) (1)

Rare Disease Felzartamab (anti-CD38 mAb) - AMR Phase 3

Felzartamab (anti-CD38 mAb) - IgAN Phase 3

Felzartamab (anti-CD38 mAb) - PMN Phase 3

Felzartamab (anti-CD38 mAb) - MVI Phase 2

Omaveloxolone (Nrf2 activator) - Pediatric FA Phase 3

Tofersen (SOD1 ASO) (1)(5) - SOD1 ALS

HD Nusinersen (SMN2 splice modulator) - SMA Regulatory Review

BIIB115 (SMN ASO) (1) - SMA

Parkinson's and Movement Disorders BIIB122 (LRRK2 inhibitor) (1) - Parkinson's

Multiple Sclerosis BIIB091 (peripheral BTK inhibitor) - MS Phase 2

Salanersen BIIB115 (SMN ASO) (1) - SMA

Zorevunersen (SCN1A ASO) (1) - Dravet syndrome

(1) Collaboration program

(2) Granted accelerated approval in the U.S.

in January 2023 and traditional approval in the U.S.

in July 2023.

Outside the U.S., LEQEMBI is now approved in Japan (September 2023), China (January 2024), South Korea (May 2024), Hong Kong (July 2024), Israel (July 2024), United Arab Emirates (August 2024), Great Britain (August 2024) and Mexico (December 2024).

(3) Granted approval in the U.S.

in August 2023, pending DEA scheduling, which was completed in October 2023, under the brand name ZURZUVAE.

(4) Granted approval in the U.S.

in February 2023 and the E.U.

in February 2024, under the brand name SKYCLARYS.

(5) Granted accelerated approval in the U.S.

in April 2023, the E.U.

in May 2024 and China in October 2024 under the brand name QALSODY.

# Option agreement

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For information about certain of our agreements with collaborators and other third parties, please read the subsection entitled Business Relationships below and Note 2, Acquisitions , Note 19, Collaborative and Other Relationships, and Note 20, Investments in Variable Interest Entities, to our consolidated financial statements included in this report.

For information about certain of our agreements with collaborators and other third parties, please read the subsection entitled Business Relationships below and Note 2, Acquisitions and Note 19, Collaborative and Other Relationships, to our consolidated financial statements included in this report.

BUSINESS RELATIONSHIPS

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Below is a brief description of certain business relationships and collaborations that expand our pipeline and provide us with certain rights to existing and potential new products and technologies.

For additional information on certain of these relationships, including their ongoing financial and accounting impact on our business, please read Note 19, Collaborative and Other Relationships , to our consolidated financial statements included in this report.

For additional information on certain

of these relationships, including their ongoing financial and accounting impact on our business, please read Note 19, Collaborative and Other Relationships , to our consolidated financial statements included in this report.

We have a collaboration agreement with Eisai to jointly develop and commercialize LEQEMBI (lecanemab), an anti-amyloid antibody for the treatment of Alzheimer's disease.

Eisai serves as the lead of LEQEMBI development and regulatory submissions globally with both companies co-commercializing and co-promoting the product, and Eisai having final decision-making authority.

Subject to the limitations in the LEQEMBI Collaboration Agreement, Eisai has final decision-making authority on all matters relating to the collaboration and serves as the lead of LEQEMBI development and regulatory submissions globally.

We co-commercialize and co-promote LEQEMBI with Eisai.

Our Collaboration Agreement provides that each commercialization plan shall allocate the responsibilities for the activities under the plan in an equitable fashion taking into account Biogen's and Eisai's respective capabilities and provides a meaningful role for each party.

All costs, including research, development, sales and marketing expense, are shared equally between us and Eisai.

We and Eisai co-promote LEQEMBI and share profits and losses equally.

We currently manufacture LEQEMBI drug substance and drug product and in March 2022 we extended our supply agreement with Eisai related to LEQEMBI from five years to ten years for the manufacture of LEQEMBI drug substance.

SAGE THERAPEUTICS, INC .

We have a global collaboration and license agreement with Sage to jointly develop and commercialize ZURZUVAE (zuranolone) for the treatment of PPD.

We also share profits and losses equally.

We currently have a supply agreement with Eisai to manufacture LEQEMBI drug substance and drug product through the end of 2031.

SUPERNUS (PREVIOUSLY SAGE)

We have a global collaboration and license agreement with Supernus to jointly develop and commercialize ZURZUVAE (zuranolone) for the treatment of PPD.

Under this collaboration, both companies will share equal responsibility and costs for development as well as profits and losses for commercialization in the U.S.

Outside of the U.S., we are responsible for development and commercialization, excluding Japan, Taiwan and South Korea.

We have several exclusive, worldwide option and collaboration agreements with Ionis to develop and commercialize antisense therapeutics, including SPINRAZA for the treatment of SMA and QALSODY for the treatment of ALS with SOD1 mutations, as well as other research programs for a broad range of neurological diseases.

Under these agreements, we have the option to license therapies arising out of these collaborations and will be responsible for their development and commercialization.

Ionis may receive potential milestones and royalties on net sales if we successfully develop the product candidate after option exercise.

We have agreements with Genentech that entitle us to certain business and financial rights with respect to RITUXAN, RITUXAN HYCELA, GAZYVA, OCREVUS, LUNSUMIO and COLUMVI, as well as the option to add other potential anti-CD20 therapies.

We have a collaboration agreement with UCB to jointly develop and commercialize dapirolizumab pegol, an anti-CD40L pegylated Fab, for the potential treatment of SLE and other future agreed indications.

Both companies will share equally costs incurred for agreed indications, including research, development, sales and marketing expense.

All costs incurred for agreed indications, including research, development, sales and marketing expense, are shared equally between us and UCB.

If marketing approval is obtained, both companies will jointly commercialize dapirolizumab pegol and share profits and losses equally.

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We have a collaboration and license agreement with Denali to co-develop and co-commercialize Denali's small molecule inhibitors of LRRK2 for Parkinson's disease.

Under these agreements, we have the option to license therapies arising out of these collaborations and will be responsible for their development and commercialization.

Ionis may receive potential milestones and royalties on net sales if we successfully develop the product candidate after option exercise.

We have worldwide, exclusive, royalty-bearing licenses to develop and commercialize salanersen (BIIB115), an investigational ASO in development for SMA and BIIB080 (tau ASO) for the potential treatment of Alzheimer's disease.

We have a collaboration and license agreement with Denali to co-develop and co-commercialize BIIB122, a small molecule inhibitor of LRRK2 for Parkinson's disease (LRRK2 Collaboration).

Under the LRRK2 Collaboration, both companies share responsibility and costs for global development based on specified percentages as well as profits and losses for commercialization in the U.S.

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and China we are responsible for commercialization and may pay Denali potential tiered royalties.

We have a collaboration and license agreement with Stoke to co-develop and commercialize zorevunersen, an investigational ASO that targets the SCN1A gene for the potential treatment of Dravet syndrome, a rare form of genetic epilepsy associated with refractory seizures and neurodevelopmental impairments.

Under this agreement, Stoke will continue to lead global development and retain exclusive development and commercialization rights for

zorevunersen in the U.S., Canada and Mexico and we will have exclusive rights to commercialize zorevunersen in the rest of the world.

SAMSUNG BIOEPIS

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Under this agreement, we are commercializing BENEPALI, an etanercept biosimilar referencing ENBREL, IMRALDI, an adalimumab biosimilar referencing HUMIRA, and FLIXABI, an infliximab biosimilar referencing REMICADE.

We have also secured the exclusive rights to commercialize BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS, in certain international markets, and OPUVIZ, an aflibercept biosimilar referencing EYLEA, which was approved in the E.U.

during the fourth quarter of 2024.

In addition to our commercialization agreements with Samsung Bioepis, we license certain of our proprietary technology to Samsung Bioepis in connection with Samsung Bioepis' development, manufacture and commercialization of its biosimilar products.

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This is a high-risk process that requires stepwise clinical studies in which the candidate product must successfully meet predetermined endpoints.

The results of the preclinical and clinical testing of a product are then submitted to the FDA in the form of a BLA or a NDA.

The results of the preclinical and clinical testing of a product are then submitted to the FDA in the form of a BLA or NDA.

In response to a BLA or NDA, the FDA may grant marketing approval, request additional information or deny the application if it determines the application does not provide an adequate basis for approval.

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The FDA has substantial discretion in the product approval process, and it is impossible to predict with any certainty whether and when the FDA will grant marketing approval.

The agency may require the sponsor of a BLA or NDA to conduct additional clinical studies or to provide other scientific or technical information about the product, and these additional requirements may lead to unanticipated delays or expenses.

Furthermore, even if a product is approved, the approval may be subject to limitations based on the FDA's interpretation of the existing pre-clinical and/or clinical data.

Furthermore, even if a product is approved, the approval may be subject to limitations based on the FDA's interpretation of the existing preclinical and/or clinical data.

The FDA has developed four distinct approaches intended to facilitate the development and expedite the regulatory review of therapeutically important drugs, especially when the drugs are the first available treatment or have advantages over existing treatments:

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When approval is based on surrogate endpoints or clinical endpoints other than survival or morbidity, the sponsor will be required to provide the FDA with confirmatory data post-approval to verify and describe clinical benefit.

Under the FDA's accelerated approval regulations, if the FDA

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concludes that a drug that has been shown to be effective can be safely used only if distribution or use is restricted, it may require certain post-marketing restrictions to assure safe use.

Under the FDA's accelerated approval regulations, if the FDA concludes that a drug that has been shown to be effective can be safely used only if distribution or use is restricted, it may require certain post-marketing restrictions to assure safe use.

In addition, for products approved under accelerated approval, sponsors may be required to submit all copies of their promotional materials, including advertisements, to the FDA at least 30 days prior to initial dissemination.

The FDA may withdraw approval if, for instance, post-marketing studies fail to verify clinical benefit, it becomes clear that restrictions on the distribution of the product are inadequate to ensure its safe use or if a sponsor fails to comply with the conditions of the accelerated approval.

The FDA may withdraw approval if, for instance, post-marketing studies fail to verify clinical benefit, it becomes clear that

restrictions on the distribution of the product are inadequate to ensure its safe use or if a sponsor fails to comply with the conditions of the accelerated approval.

• Fast Track :

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FDA regulatory review may result in denial or modification of the planned changes, or requirements to conduct additional tests or evaluations that can substantially delay or increase the cost of the planned changes.

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REGULATION OF PRODUCT ADVERTISING AND PROMOTION

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Such off-label prescribing is common across medical specialties, and often reflects a physician's belief that the off-label use is the best treatment for patients.

The FDA does not regulate the behavior of physicians in their choice of treatments, but FDA regulations do impose stringent restrictions on manufacturers' communications regarding off-label uses.

The FDA does not regulate the behavior of physicians in their choice of treatments, but FDA regulations do impose stringent restrictions on manufacturers'

communications regarding off-label uses.

Failure to comply with applicable FDA requirements may subject a company to adverse publicity, enforcement action by the FDA, corrective advertising and the full range of civil and criminal penalties available to the government.

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These regulations also change the requirements for assessment of the medical device components of integral drug-device combination products, necessitating assessment of the device components under both the medical device and medicinal product regulatory regimes.

On May 6, 2024, the FDA issued a Final Rule that explicitly states that in-vitro diagnostic products are medical devices under the Federal Food, Drug and Cosmetic Act, even when manufactured by clinical laboratories.

This includes laboratory developed tests, which historically operated under FDA's enforcement discretion and were largely unregulated by the agency.

PRODUCT APPROVAL AND POST-APPROVAL REGULATION OUTSIDE THE U.S.

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The CHMP opinion is not binding, but is typically adopted by the EC.

A MAA approved by the EC is valid in all member states of the E.U.

An MAA approved by the EC is valid in all member states of the E.U.

The centralized procedure is required for all biological products, orphan medicinal products and new treatments for neurodegenerative disorders, and it is available for certain other products, including those which constitute a significant therapeutic, scientific or technical innovation.

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may be truncated under accelerated assessment for products that address an unmet medical need.

In addition, conditional marketing authorizations may be granted for products in the interest of public health, where the benefit of immediate availability

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outweighs the risk of having less comprehensive data than normally required.

In addition, conditional marketing authorizations may be granted for products in the interest of public health, where the benefit of immediate availability outweighs the risk of having less comprehensive data than normally required.

Conditional marketing authorizations are valid for one year and can be renewed annually.

The marketing authorization holder is required to complete specific obligations (ongoing or new studies and, in some cases, additional activities) with a view to providing comprehensive data confirming that the benefit risk balance is positive.

The marketing authorization holder is required to complete specific obligations (ongoing or new studies and, in some cases, additional activities) with a view to providing

comprehensive data confirming that the benefit risk balance is positive.

Once comprehensive data on the product have been obtained, the marketing authorization may be converted into a standard marketing authorization.

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the PPACA amended the PHS Act to authorize the FDA to approve biological products, referred to as biosimilars or follow-on biologics, that are shown to be "highly similar" to previously approved biological products based upon potentially abbreviated data packages.

The biosimilar must show it has no clinically meaningful

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differences in terms of safety and effectiveness from the reference product, and only minor differences in clinically inactive components are allowable in biosimilar products.

The approval pathway for biosimilars does, however, grant a biologics manufacturer a 12-year period of exclusivity from the date of approval of its biological product before biosimilar competition can be introduced.

The biosimilar must show it has no clinically meaningful differences in terms of safety and effectiveness from the reference product, and only minor differences in clinically inactive components are allowable in biosimilar products.

The approval pathway for biosimilars does, however, grant a biologics manufacturer a 12-year period of exclusivity from the date of approval of its biological product before

biosimilar competition can be introduced.

There is uncertainty, however, as the approval framework for biosimilars originally was enacted as part of the PPACA.

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for development in the treatment of PMN and AMR and in the E.U.

in IgAN and solid organ transplantation.

in PMN, IgAN and solid organ transplantation.

REGULATION PERTAINING TO PRICING AND REIMBURSEMENT

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In addition, if we fail to provide information timely or we are found to have knowingly submitted false information to the government, the statute governing the Medicaid Drug Rebate Program provides for civil monetary penalties.

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Medicare is a federal program that is administered by the federal government.

The program covers individuals age 65 and over as well as those with certain disabilities.

Medicare Part B generally covers drugs that must be administered by physicians or other health care practitioners, are provided in connection with certain durable medical equipment or are certain oral anti-cancer drugs and certain oral immunosuppressive drugs.

Medicare Part B generally covers drugs that must be administered by physicians or other health care practitioners, are provided in connection with

certain durable medical equipment or are certain oral anti-cancer drugs and certain oral immunosuppressive drugs.

Medicare Part B pays for such drugs under a payment methodology based on the average sales price of the drugs.

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The prescription drug plans negotiate pricing with manufacturers and pharmacies, and may condition formulary placement on the availability of manufacturer discounts.

In addition, manufacturers, including us, are required to provide to the CMS a discount of up to 70.0% on brand name prescription drugs utilized by Medicare Part D beneficiaries when those beneficiaries reach the coverage gap in their drug benefits.

On August 16, 2022, the IRA was signed into law, which provides for (i) the government to negotiate prices for select high-cost Medicare Part D drugs (beginning in 2026) and Part B drugs (beginning in 2028), (ii) manufacturers to pay a rebate for Medicare Part B and Part D drugs when prices increase faster than inflation beginning in 2022 for Part D and 2023 for Part B, and (iii) Medicare Part D redesign which replaces the current coverage gap provisions and establishes a $2,000 cap for out-of-pocket costs for Medicare beneficiaries beginning in 2025, with manufacturers being responsible for up to 10.0% of costs up to the $2,000 cap and up to 20.0% after that cap is reached.

The result of these forthcoming changes for manufacturers, including us, may include:

In addition, up until 2024, manufacturers, including us, were required to provide to the CMS a discount of up to 70.0% on brand name prescription drugs utilized by Medicare Part D beneficiaries when those beneficiaries reach the coverage gap in their drug benefits.

On August 16, 2022, the IRA was signed into law, which provides for (i) the government to negotiate prices for select high-cost Medicare Part D drugs (beginning in 2026) and Part B drugs (beginning in 2028), (ii) manufacturers to pay a rebate for Medicare Part B and Part D drugs when prices increase faster than inflation beginning in 2022 for Part D and 2023 for Part B, and (iii) Medicare Part D redesign which replaces the previous coverage gap provisions and establishes a $2,000 cap for out-of-pocket costs for Medicare beneficiaries beginning in 2025 (indexed to increase in future years), with manufacturers being responsible for up to 10.0% of costs up to the patient's out-of-pocket cap and up to 20.0% after that cap is reached.

The result of these changes for manufacturers, including us, may include:

i) a material adverse effect on our revenue on drugs subject to “negotiation”;

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Governments may use a variety of cost-containment measures to control the cost of products, including price cuts, mandatory rebates, value-based pricing and reference pricing (i.e., referencing prices in other countries and using those reference prices to set a price).

Budgetary pressures in many countries are continuing to cause governments

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to consider or implement various cost-containment measures, such as price freezes, increased price cuts and rebates and expanded generic substitution and patient cost-sharing.

Budgetary pressures in many countries are continuing to cause governments to consider or implement various cost-containment measures, such as price freezes, increased price cuts and rebates and expanded generic substitution and patient cost-sharing.

REGULATION PERTAINING TO SALES AND MARKETING

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The laws and regulations generally limit financial interactions between manufacturers and health care providers or require disclosure to the government and public of such interactions.

The laws include federal “sunshine” provisions.

The laws include federal and state “sunshine” transparency reporting provisions.

The sunshine provisions apply to pharmaceutical manufacturers with products reimbursed under certain government programs and require those manufacturers to disclose annually to the federal government (for re-disclosure to the public) certain payments made to physicians and certain other healthcare practitioners or to teaching hospitals.

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National Institutes of Health Guidelines for Research Involving Recombinant DNA Molecules (NIH Guidelines).

By local ordinance, we are required to, among other things, comply with the NIH Guidelines in relation to our facilities in RTP, North Carolina and are required to operate pursuant to certain permits.

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By local ordinance, we are required to, among other things, comply with the NIH Guidelines in relation to our facilities in RTP and are required to operate pursuant to certain permits.

Our present and future business has been and will continue to be subject to various other laws and regulations.

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In addition, several U.S.

jurisdictions have similar data privacy laws, such as the CCPA and California Privacy Rights Act.

state jurisdictions have similar data privacy laws, such as the CCPA and California Privacy Rights Act.

MANUFACTURING

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To that end, we regularly review our manufacturing capacity, capabilities, processes and facilities.

In order to support our future growth and drug development pipeline, we expanded our large molecule production capacity and built a large-scale biologics manufacturing facility in Solothurn, Switzerland.

The Solothurn facility is operational and has been approved for the manufacture of LEQEMBI and TYSABRI.

We believe that the Solothurn facility will support our anticipated near to mid-term needs for the manufacturing of biologic assets.

The plant represents a significant increase in our overall manufacturing capacity.

Additionally, we continue to invest to modernize, automate and support the capacity requirements for our pipeline and existing products at our existing manufacturing facilities in RTP, North Carolina.

We believe that our manufacturing facilities, together with the third-party contract manufacturing organizations we outsource to, currently provide sufficient capacity for our products and to Samsung Bioepis, our collaboration partner that develops, manufactures and markets biosimilar products, and other strategic contract manufacturing partners.

In the fourth quarter of 2021 we began construction of a new gene therapy, clinical packaging and other manufacturing facility in RTP, North Carolina to support our gene therapy pipeline across multiple therapeutic areas.

We estimate the construction of this manufacturing facility will be completed during 2025.

As we continue to advance our research and development prioritization efforts, which includes refocusing our investment in gene therapy, we are evaluating several alternative uses for this facility.

MANUFACTURING FACILITIES

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FACILITY PRODUCT MANUFACTURED

RTP, North Carolina AVONEX

Research Triangle Park, North Carolina AVONEX

Solothurn, Switzerland LEQEMBI

* Other includes products manufactured for contract manufacturing partners.

In addition to our drug substance manufacturing facilities, we have a drug product manufacturing facility and supporting infrastructure in RTP, North Carolina, including a parenteral facility and an oral solid dose products manufacturing facility.

In addition to our drug substance manufacturing facilities, we have a drug product manufacturing facility and supporting infrastructure in RTP, including a parenteral facility and an oral solid dose products manufacturing facility.

The parenteral facility adds capabilities and capacity for filling biologics into vials and is used for filling product candidates.

The oral solid dose products facility can supplement our outsourced small molecule manufacturing capabilities.

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We have an oligonucleotide synthesis manufacturing facility in RTP, North Carolina.

We have an oligonucleotide synthesis manufacturing facility in RTP.

This facility gives us the capability to manufacture both commercial and clinical ASOs, including QALSODY, and beginning in 2026 this facility will manufacture SPINRAZA.

In order to support our future growth and drug development pipeline, we built a large-scale biologics manufacturing facility in Solothurn, Switzerland.

In the second quarter of 2021 a portion of the facility (the first manufacturing suite) received a GMP multi-product license from SWISSMEDIC and was placed into service.

The second manufacturing suite, which was also licensed to operate by SWISSMEDIC, became operational in the first quarter of 2024.

Solothurn has been approved for the manufacture of LEQEMBI.

Additionally, in 2025 we acquired a sterile fill finish manufacturing facility in Athlone, Ireland.

This facility will provide us with the capability for syringe and cartridge sterile fill finish across our current manufacturing network, incorporating our MS product portfolio and our late-stage portfolio including litifilimab and felzartamab.

Genentech is responsible for all worldwide manufacturing activities for bulk RITUXAN, RITUXAN HYCELA and GAZYVA and has sourced the manufacture of certain bulk requirements to a third party.

THIRD-PARTY SUPPLIERS AND MANUFACTURERS

We principally use third parties to manufacture the active pharmaceutical ingredient and the final product for our small molecule products and product candidates, including TECFIDERA, VUMERITY and FUMADERM, and the final drug product for our large molecule products and, to a lesser extent, product candidates.

We principally use third parties to manufacture the active pharmaceutical ingredient and the final product for our small molecule products and product candidates, including TECFIDERA, VUMERITY, SKYCLARYS and ZURZUVAE, and the final drug product for our large molecule products and, to a lesser extent, product candidates.

We source the majority of our fill-finish and all of our final product assembly and storage operations for our products, along with a substantial part of our label and packaging operations, to a concentrated group of third-party contract manufacturing organizations.

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Our third-party service providers, suppliers and manufacturers may be subject to routine cGMP inspections by the FDA or comparable agencies in other jurisdictions and undergo assessment and certification by our quality management group.

In addition, one of our contract manufacturers for IMRALDI and BENEPALI was acquired by a third party in December 2024.

We have evaluated the impact this will have on our biosimilars business and have mitigation activities in progress designed to ensure supply continuity.

CORPORATE RESPONSIBILITY

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We remain committed to engaging employees and suppliers.

As part of our broader commitment to these priorities, we continue to tie a portion of our employees' and executive officers' compensation to advancing our Corporate Responsibility priorities.

As part of our broader commitment to these priorities, we continue to link a portion of our employees' and executive officers' compensation to advancing our Corporate Responsibility goals.

Our Executive Committee has responsibility for evaluating the impact of climate change on the business and overseeing actions taken by the company to limit its adverse impact on the environment.

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Our Board of Directors oversees an enterprise-wide approach to risk management, which is designed to support execution of our strategy and achievement of our objectives to improve long-term operational and financial performance and enhance stockholder value.

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We have a company-wide ERM program to identify, mitigate and monitor enterprise-level risks that may affect our ability to achieve our objectives.

The ERM program is overseen by our ERM Committee, a cross-functional group of business leaders representing all of our key business functions.

The ERM program is overseen by our ERM Committee, a cross-functional group of

business leaders representing all of our key business functions.

On an ongoing basis, we evaluate the greatest risks to our business, their underlying risk drivers and the associated mitigation activities and controls.

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Our values and merit-based culture guide every action we take, from pioneering new therapies to promoting health access for all patients.

To continue to build on our strong culture, we implemented the New Biogen Way, aimed at maintaining our spirit of innovation and patient-centricity while advancing a more entrepreneurial business mindset and results-focused approach.

Our culture is underpinned by the New Biogen Way, aimed at maintaining our spirit of innovation and patient-centricity while advancing an entrepreneurial business mindset and results-focused approach.

These are the essentials that are designed to work together to help us successfully achieve our mission:

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PIONEER THINK BROADLY DRIVE RESULTS

We boldly advance rigorous science to drive innovation in medicine.

Think broadly:

We are humble and curious, integrating external and internal advancements to successfully compete.

Drive results:

We achieve high performance and have a greater impact by being decisive and solution-oriented, while effectively managing risk.

ETHICAL INCLUSIVE

We act with the highest integrity with each other and all who place their trust in us.

We are open and embrace and leverage differences, as well as treat everyone with care and dignity.

We use an employee survey program to understand employee engagement, giving employees an opportunity for feedback.

We utilize an annual survey to provide employees with an opportunity to provide feedback and to measure employee engagement.

The survey is designed to empower managers and leaders with anonymous information on their practices related to building culture, performance and an engaged workforce, allowing them to create plans and measure efficacy for continuous improvement.

We care about employee feedback and are building an analytics community across Human Resources to bring more rigor and sophistication to the collection and analysis of employee opinions.

We use those employee perspectives to guide us to take actions that are designed to improve engagement and support and help maintain our reputation as a great place to work for all our employees.

We use those employee perspectives to guide us in taking actions that are designed to improve engagement and support and help maintain our reputation as a great place to work for all our employees.

GLOBAL COMPETENCY

Many factors influence employee success and well-being.

We work to foster a workplace to allow employees to deliver on our shared mission.

From career development to wellness to workplace environment, there are many opportunities to meet employee needs, and to build a workplace where people are empowered to learn, grow and build rewarding careers.

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Development occurs through on-the-job learning, challenging new assignments, leadership development programs, instructor-led training, online learning, mentoring and more.

With some employees continuing to work from home, virtual learning plays a key role.

Virtual learnings are available through Biogen University as well as Coursera.

With some employees working remotely, virtual learning plays a key role.

We utilize online resources such as Biogen University, Coursera and Franklin Covey.

To create and sustain an inclusive workplace reflective of the patients we serve, we offer programs that invest in our talent pipeline and in our current leaders, including:

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Each year we conduct a talent review across our global enterprise that includes, among other important topics, a review of succession plans for many of our roles.

To help ensure the long-term continuity of our business, we actively manage the development of talent to fill the roles that are most critical to the ongoing success of our Company.

To help ensure the long-term continuity of our business, we actively manage the development of talent to fill the roles that are most critical to our ongoing success.

In addition, each year our Board of Directors reviews the succession plan for our executives.

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We regularly review our compensation practices and analyze the fairness of compensation decisions, for individual employees and our workforce as a whole.

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RECRUITMENT AND RETENTION

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Creates networking, mentoring and learning opportunities for women and allies worldwide.

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INFORMATION ABOUT OUR EXECUTIVE OFFICERS (as of February 6, 2026)

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Alexander Executive Vice President, Chief Legal Officer 69 2006

McDonnell (1)

Executive Vice President and Chief Financial Officer 61 2020

Kramer Executive Vice President and Chief Financial Officer 60 2018

Nicole Murphy Executive Vice President, Pharmaceutical Operations and Technology 53 2015

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Executive Vice President, Head of Corporate Development 49 2023

Senior Vice President, Chief Accounting Officer 59 2018

(1) Michael R.

McDonnell, Executive Vice President and Chief Financial Officer, plans to retire from Biogen on March 1, 2025.

McDonnell's retirement, Robin C.

Kramer, currently Senior Vice President and Chief Accounting Officer at Biogen, will assume the role of Executive Vice President and Chief Financial Officer.

Sean Godbout Vice President, Chief Accounting Officer and Global Corporate Controller 52 2007

Christopher A.

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Viehbacher previously served on the board of directors of Vedanta Biosciences, Inc.

as chair, BEFORE Brands, Inc., and Crossover Health.

He is also a trustee of Northeastern University and a member of the board of fellows at Stanford Medical School.

as chair, BEFORE Brands, Inc., Crossover Health, Sanofi and GlaxoSmithKline.

He is also the chair of the board of directors at Braveheart Bio, Inc., a trustee of Northeastern University and a member of the board of fellows at Stanford Medical School.

l Queen's University in Kingston, Ontario, Canada, B.A.

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l Boston University School of Law, J.D.

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McDonnell has served as our Executive Vice President and Chief Financial Officer since August 2020.

Prior to joining Biogen, Mr.

McDonnell served as Executive Vice President and Chief Financial Officer of IQVIA Holdings Inc., a leading global provider of advanced analytics, technology solutions and contract research services to the life sciences industry, from December 2015 until July 2020.

Prior to that, Mr.

McDonnell served as the Executive Vice President and Chief Financial Officer of Intelsat, a leading global provider of satellite services, from November 2008 to December 2015, as Executive Vice President and Chief Financial Officer of MCG Capital Corporation, a publicly-held commercial finance company, from September 2004 until October 2008 and as MCG Capital Corporation’s Chief Operating Officer from August 2006 until October 2008.

Before joining MCG Capital Corporation, Mr.

McDonnell served as Executive Vice President and Chief Financial Officer for EchoStar Communications Corporation (f/k/a DISH Network Corporation), a direct-to-home satellite television operator, from July 2004 until August 2004 and as its Senior Vice President and Chief Financial Officer from August 2000 to July 2004.

McDonnell spent 14 years at PricewaterhouseCoopers LLP, including 4 years as a partner.

McDonnell is a licensed certified public accountant (CPA).

Kramer has served as our Chief Financial Officer since March 2025.

Prior to that, Ms.

Kramer served as our Senior Vice President, Chief Accounting Officer from December 2020 to February 2025 and from November 2018 to December 2020 as our Vice President, Chief Accounting Officer.

Prior to joining Biogen, Ms.

Kramer served as the Senior Vice President and Chief Accounting Officer of Hertz Global Holdings, Inc., a car rental company, from May 2014 to November 2018.

Prior to that, Ms.

Kramer was an audit partner at Deloitte & Touche LLP (Deloitte), a professional services firm, from 2007 to 2014, including serving in Deloitte's National Office Accounting Standards and Communications Group from 2007 to 2010.

From 2005 to 2007 Ms.

Kramer served as Chief Accounting Officer of Fisher Scientific International, Inc., a laboratory supply and biotechnology company, and from 2004 to 2005 Ms.

Kramer served as Director, External Reporting, Accounting and Control for the Gillette Company, a personal care company.

Kramer also held partner positions in the public accounting firms of Ernst & Young LLP and Arthur Andersen LLP.

Kramer is a licensed CPA in Massachusetts.

She is a member of the Massachusetts Society of CPAs and the American Institute of CPAs.

Kramer previously served as a Board Member for the Center for Women & Enterprise from August 2020 to November 2024, the Massachusetts State Board of Accountancy from September 2011 to December 2015 and Probus Insurance Company Europe DAC from 2016 to 2018.

Public Company Boards

l Merit Medical Systems, Inc.

l Georgetown University, B.S.

l Armata Pharmaceuticals, Inc., a biotechnology company

l Salem State University, B.S.

Business Administration, Accounting

Nicole Murphy

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l The George Washington University, Ph.D.

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Izzar has served as our Executive Vice President, Head of Global Product Strategy and Commercialization since July 2021.

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l University of Melbourne, B.Sc in Biochemistry and Pharmacology

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Adam Keeney, Ph.D.

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Prior to NodThera, Dr.

Keeney was at Sanofi from 2014 to 2018 where he had responsibility for all of Sanofi Gezyme's business development activities, including early- and late-stage deals across therapeutic areas and modalities, successfully completing several significant transactions.

Keeney was at Sanofi from 2014 to 2018 where he had responsibility for all of Sanofi Genzyme's business development activities, including early- and late-stage deals across therapeutic areas and modalities, successfully completing several significant transactions.

From 2004 to 2013 Dr.

3 unchanged sentences

l University of Leeds, UK, BSc (Hons)

Kramer has served as our Senior Vice President, Chief Accounting Officer since December 2020.

Prior to that, Ms.

Kramer served as our Vice President, Chief Accounting Officer from November 2018 to December 2020.

Prior to joining Biogen, Ms.

Kramer served as the Senior Vice President and Chief Accounting Officer of Hertz Global Holdings, Inc., a car rental company, from May 2014 to November 2018.

Prior to that, Ms.

From 2005 to 2007 Ms.

Kramer served as Chief Accounting Officer of Fisher Scientific International, Inc., a laboratory supply and biotechnology company, and from 2004 to 2005 Ms.

Kramer served as Director, External Reporting, Accounting and Control for the Gillette Company, a personal care company.

Kramer also held partner positions in the public accounting firms of Ernst & Young LLP and Arthur Andersen LLP.

Kramer is a licensed CPA in Massachusetts.

She is a member of the Massachusetts Society of CPAs and the American Institute of CPAs.

Public Company Boards

l Armata Pharmaceuticals, Inc., a biotechnology company

l Salem State University, Bachelor of Science in Business Administration, Accounting

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Godbout has served as our Vice President, Chief Accounting Officer and Global Corporate Controller since March 2025.

Prior to that, Mr.

Godbout served as our Global Corporate Controller from October 2023 to February 2025 and Corporate Controller from September 2019 to October 2023 and has held roles of increasing seniority at the Company since 2007.

Prior to joining Biogen, Mr.

Godbout spent 10 years at PricewaterhouseCoopers LLP and he is a licensed CPA.

l Cornell University, B.S.

Industrial and labor Relations

l Northeastern University, M.S.

Accounting and Masters of Business Administration

AVAILABLE INFORMATION

5 unchanged sentences

USE OF WEBSITE TO PROVIDE INFORMATION

From time to time, we have used, and expect in the future to use, our website as a means of disclosing material information to the public in a broad, non-exclusionary manner, including for purposes of the SEC’s Regulation Fair Disclosure (Reg FD).

Financial and other material information regarding the Company is routinely posted on our website and accessible at www.biogen.com.

In order to receive notifications regarding new postings to our website, investors are encouraged to enroll on our website to receive automatic email alerts.

None of the information on our website is incorporated into this report.

Table o f Contents

From time to time, we have used, or expect in the future to use, our investor relations website (investors.biogen.com), the Biogen LinkedIn account (linkedin.com/company/biogen/-) and the Biogen X account (https://x.com/biogen) as a means of disclosing information to the public in a broad, non-exclusionary manner, including for purposes of the SEC’s Regulation Fair Disclosure (Reg FD).

Accordingly, investors should monitor our investor relations website and these social media channels in addition to our press releases, SEC filings, public conference calls and websites, as the information posted on them could be material to investors.

Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 1. Business