Biogen (BIIB) 10-K risk factor changes: FY2025 vs FY2024

Any of the following negative developments relating to any of our products or any of our anti-CD20 therapeutic programs may adversely affect our revenue and results of operations or [removed: could cause a decline in] our stock price:

- limitations and additional pressures on product pricing or price increases, including those relating to inflation and those resulting from governmental or regulatory requirements, including those relating to any future potential drug price negotiation under the [removed: IRA;] [added: IRA or other legislative or executive acts;] increased competition, including from generic or biosimilar versions of our products; or changes in, or implementation of, reimbursement policies and practices of payors and other [removed: third-parties;][added: third parties;]

- adverse legal, administrative, [removed: geopolitical events,] [added: geopolitical,] regulatory or legislative developments; [removed: or][added: and]

LEQEMBI is in the early stages of commercial launch in the U.S. and certain international markets and SKYCLARYS is in the early stages of commercial launch in [removed: the U.S. and] certain European markets.

- the approval [added: and/or greater acceptance] of other new products for the same or similar indications;

Our long-term success [removed: will depend] [added: depends] upon the successful development of new products from our research and development activities or our licenses or acquisitions from third parties, as well as [added: the development of] additional indications for our existing products.

Product development is very expensive and involves a high degree of uncertainty and risk and [removed: may] [added: is] not [removed: be] [added: always] successful.

The development of novel approaches for the treatment of diseases, including development efforts in new modalities such as those based on the [removed: antisense oligonucleotide platform and gene therapy,] [added: ASO platform,] presents additional challenges and risks, including obtaining approval from regulatory authorities that have limited experience with the development of such therapies.

For example, we are currently seeking approval of [removed: LEQEMBI in Europe and the approval of] a subcutaneous formulation of LEQEMBI [added: as a starting dose] in the U.S. and any delays or challenges may impact our ability to realize the anticipated benefits from LEQEMBI.

Clinical trial data are subject to differing interpretations and even if we view data as sufficient to support the safety, effectiveness and/or approval of [removed: an investigational therapy,] [added: a product candidate,] regulatory authorities may disagree and may require additional data, limit the scope of the approval or deny approval altogether.

Success in preclinical work or [removed: early-stage] [added: early stage] clinical trials does not ensure that later stage or larger scale clinical trials will be successful.

This may result in terminated programs, significant restrictions on [removed: use and] [added: use,] safety warnings in an approved label, adverse placement within the treatment paradigm or significant reduction in the commercial potential of the product candidate.

Even if we could successfully develop new products or [removed: indications,] [added: additional indications for our existing products,] we may make a strategic decision to discontinue development of a product candidate or [added: an additional] indication [added: for our existing products] if, for example, we believe commercialization will be difficult relative to the standard of care or we prioritize other opportunities in our pipeline.

We compete with [removed: biotechnology and pharmaceutical] companies that have a greater number of products on the market and in the product pipeline, substantially greater financial, marketing, research and development and other [removed: resources] [added: resources,] and other technological or competitive advantages.

The introduction of such products as well as other lower-priced competing products has [added: in the past] reduced, and may in the [removed: future,] [added: future] significantly [removed: reduce] [added: reduce,] both the price that we are able to charge for our products and the volume of products we sell, which [removed: will] [added: has and may continue to] negatively impact our revenue.

Our ability to compete, maintain and grow our business may [removed: also] be adversely affected [removed: due to] [added: by] a number of factors, including:

- inability to obtain and maintain appropriate pricing and adequate reimbursement for our products compared to our competitors in key markets; [removed: or][added: and]

The successful execution of our strategic and growth initiatives depends upon internal development projects, commercial initiatives and external opportunities, which may include the acquisition and in-licensing of products, technologies, companies, the entry into strategic alliances and [removed: collaborations or our Fit for Growth program,] [added: collaborations,] as well as our ability to execute on strategic decisions and initiatives.

The availability of high quality, fairly valued external product development is limited and the opportunity [removed: for their acquisition] [added: to acquire or in-license] is highly competitive.

As such, we are not certain that we will be able to identify suitable candidates for acquisition or [added: in-licensing or] if we will be able to reach agreement to make any such acquisition [added: or in-license] if suitable candidates are identified.

Furthermore, we may not be able to achieve the full strategic and financial benefits expected to result from [removed: transactions] [added: transactions, collaborations] or strategic decisions, such as the decision to retain the biosimilars business, or the benefits may be delayed or not occur at all.

Sales of our products depend, to a significant extent, on [added: the availability and extent of] adequate coverage, pricing and reimbursement from [removed: third-party payors,] [added: government health administration authorities, private health insurers and other organizations,] which are subject to increasing and intense pressure from political, social, competitive and other sources.

Sales of our products depend, to a significant extent, on [added: the availability and extent of] adequate coverage, pricing and reimbursement from [removed: third-party payors.][added: governmental health administration authorities, private health insurers and other organizations.]

- consolidation and increasing assertiveness of [removed: payors] [added: governmental health administration authorities, private health insurers and other organizations] seeking price discounts or rebates in connection with the placement of our products on their formularies and, in some cases, the imposition of restrictions on access or coverage of particular drugs or pricing determined based on perceived value;

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 [added: countries and using those reference prices to set a price).]

We expect drug pricing and other [removed: health care] [added: healthcare] costs to continue to be subject to [removed: intense] political [removed: and] [added: or] societal pressures on a global basis.

[removed: Our inability to obtain and] maintain adequate prices in a particular country [added: has limited, and] may [removed: not only limit] [added: in] the [added: future limit, the] revenue from our products within that country [removed: but] [added: and has, and] may [added: in the future,] also adversely affect our ability to secure acceptable prices in existing and potential new markets, which [added: has limited, and] may [removed: limit] [added: in the future limit,] market growth and result in reductions in revenue.

This [added: has created, or] may [removed: create] [added: create,] the opportunity for third-party cross-border trade or influence our decision to sell or not to sell a product, thus adversely affecting our geographic expansion plans and revenue.

Additionally, in certain jurisdictions governmental health agencies [removed: may] [added: are permitted to] adjust, retroactively and/or prospectively, reimbursement rates for our products.

Reimbursement for our products by governments, including the timing of any reimbursements, [removed: may] [added: are] also [removed: be] affected by budgetary or political constraints, particularly in challenging economic environments.

In addition, these agencies experience political pressure that [removed: may] dictate the manner in which they spend money.

Competition from current and future competitors [added: has and] may [added: continue to] negatively impact our ability to maintain pricing and our market share.

New products marketed by our competitors [added: have caused and] could [added: continue to] cause our revenue to decrease due to potential price reductions and lower sales volumes.

Additionally, the introduction of generic or biosimilar versions of our products, follow-on products, prodrugs or products approved under abbreviated regulatory pathways [added: has and] may [added: continue to] significantly reduce the price [removed: that we are able to charge for our products] and the volume of products we sell.

Many [added: third-party] payors continue to adopt benefit plan changes that shift a greater portion of prescription costs to patients, including more limited benefit plan designs, higher patient co-pay or co-insurance obligations and limitations on patients' use of commercial manufacturer co-pay payment assistance programs (including through co-pay accumulator adjustment or maximization programs).

Our failure to obtain or maintain adequate coverage, pricing or reimbursement for our products could have an adverse effect on our business, reputation, revenue and results of [removed: operations.][added: operations, could curtail or eliminate our ability to adequately fund research and development programs and/or could cause a decline or volatility in our stock price.]

We depend on relationships with collaborators and other [removed: third-parties] [added: third parties] for revenue, and for the development, regulatory approval, commercialization and marketing of certain of our products and product candidates, which are outside of our full control, and if these relationships fail, our business may be adversely affected.

We also outsource certain aspects of our regulatory affairs and clinical development relating to our products and product candidates to [removed: third-parties.][added: third parties.]

Reliance on [removed: third-parties] [added: third parties] subjects us to a number of risks, including:

- we may be unable to control the resources our collaborators or [removed: third-parties] [added: third parties] devote to our programs, products or product candidates, which may affect our ability to achieve development goals or milestones;

Our inability to obtain and

- disruptions, turnover or changes in strategy, priorities or capabilities at our collaborators resulting from, for example, a change in control, may impact the commercialization or manufacturing of our shared products and may result in loss of revenue or higher operating expense; and

In July 2025 the U.S. signed into law the OBBBA, which enacts significant potential changes to Medicaid funding and rescinds or does not continue elements of the PPACA.

The OBBBA implements additional eligibility rules on government health plans, expands administrative procedures around enrollment, modifies how states can obtain federal funding for Medicaid and no longer extends ACA premium subsidies.

Additional federal and state guidance is expected to be issued in order to implement these OBBBA provisions, most of which have effective dates in 2027 and 2028.

At this time, we are unable to determine the overall impact that the OBBBA will have on our business, results of operations and financial condition, or the impact the OBBBA will have on the pharmaceutical industry as a whole because any such impact will depend upon developing interpretations of the OBBBA provisions and implementing regulations, which may be material.

We face uncertainties regarding potential healthcare reforms, governmental policy and prioritization.

For example, we expect the IRA's drug pricing controls and Medicare Part D redesign to have an adverse impact on sales, particularly for our products that are more substantially reliant on Medicare reimbursement.

Additionally, the current government administration has introduced various measures to address prescription drug pricing and access, including through issuance of an executive order aiming to establish an MFN drug pricing policy that would tie U.S. drug prices to the prices paid for drugs in other developed countries.

If HHS sets MFN pricing targets for prescription drugs, including the use of international pricing reference to set drug prices in the U.S., or if legislation is passed enabling generic drug or biosimilar entry sooner than expected, our business could be materially harmed, including with respect to our ability to set adequate pricing for new drugs to recover our research and development costs.

Additional proposals, regulations or initiatives related to drug pricing, such as the CMS-proposed MFN initiatives, the Global Benchmark for Efficient Drug Pricing for certain Medicare Part B drugs and the Guarding U.S. Medicare Against Rising Drug Costs for certain Medicare Part D drugs, continue to be debated, and additional executive orders or regulatory initiatives focused on drug pricing and competition may be adopted and implemented in some form.

The timing and extent of implementation of any of the measures described above is uncertain and we cannot fully predict their impact on our product candidates and our business.

The adoption of these and any other government controls and measures, and tightening of restrictive policies in jurisdictions with existing controls and measures, could exclude or limit our product candidates from coverage, limit payments for

pharmaceuticals, limit our ability to launch products in certain markets and impact healthcare systems and drug markets in the U.S. and abroad, thereby negatively affecting our revenue and adversely impacting our business.

In addition, our increased use of cloud technologies heightens these and other operational risks, and any failure by cloud or other

These third parties are independent entities subject to their own unique operational, strategic and financial risks that are outside of our control and may be affected by events outside of our control.

Healthcare companies are facing heightened scrutiny of their

For example, the U.S. federal government has initiated Section 232 investigations including with respect to pharmaceutical imports into the U.S. The result of these Section 232 investigations and any subsequent rulemaking could result in the government taking actions such as trade protection measures, embargoes, import or export licensing requirements, the imposition of trade sanctions or similar restrictions, which could have adverse consequences to our business and operations.

Our ability to repurchase shares will depend upon, among other factors, our cash balances and potential future capital

Our estimates concerning the impact of the OBBBA remain subject to developing interpretations of the provisions of the OBBBA, which may require further adjustments and changes in our estimates, and could have a material adverse effect on our business.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

Additionally, sales of new products or products with additional indications may not meet investor expectations.

For instance, demand and price for TECFIDERA declined significantly as a result of multiple TECFIDERA generic entrants entering the U.S. market in 2020.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

For example, we recently acquired Reata and HI-Bio and are in the process of integrating Reata and HI-Bio into our Company.

The ultimate success of our acquisitions of Reata and HI-Bio and our ability to realize the anticipated benefits from the acquisitions, including future performance of the SKYCLARYS product and further development of the felzartamab product and anticipated synergies, depends on, among other things, how effective we are in integrating the Biogen, Reata and HI-Bio operations.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

countries and using those reference prices to set a price).

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

could result in termination of the research, development or commercialization of product candidates or could result in litigation or arbitration;

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

For example, one of our contract manufacturers for IMRALDI and BENEPALI was acquired by a third party in December 2024, which may have an impact on our biosimilars business;

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

For example, a recently completed acquisition of a contract development and manufacturing organization by a third party may impact its operational, strategic or financial risk.

If microbial, viral or other contaminations are discovered

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

may have different product distribution methods, marketing programs or patient assistance programs from those we currently utilize or support.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

Charges resulting from excess capacity may continue to occur and would have a negative effect on our financial condition and results of operations.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

at risk for a number of dangerous health consequences.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

impairment charges or additional depreciation when the expected useful lives of certain assets have been shortened due to the anticipated closing of facilities.

Upon a change in control, some of these provisions could trigger reduced milestone, profit or royalty

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

These initiatives focus on common international principles for the entitlement to taxation of global corporate profits and minimum global tax rates.

Additionally, other regulators are considering environmental disclosure rules.

For our discussion of the year ended December 31, [removed: 2023,] [added: 2024,] compared to the year ended December 31, [removed: 2022,] [added: 2023,] please read *Item 7.* *Management's Discussion and Analysis of Financial Condition and Results of Operations* located in our Annual Report on Form 10-K for the year ended December 31, [removed: 2023.][added: 2024.]

We market the first and only drug approved in the [removed: U.S. and] [added: U.S.,] the E.U. [added: and certain international markets] for the treatment of FA in adults and adolescents aged 16 years and older.

Our marketed products include [removed: TECFIDERA,] VUMERITY, [removed: AVONEX, PLEGRIDY] [added: TYSABRI, TECFIDERA, AVONEX] and [removed: TYSABRI] [added: PLEGRIDY] for the treatment of MS; SPINRAZA for the treatment of SMA; SKYCLARYS for the treatment of FA; [removed: QALSODY for the treatment of ALS;] and [removed: FUMADERM] [added: QALSODY] for the treatment of [removed: severe plaque psoriasis.][added: ALS.]

We also have collaborations with Eisai on the commercialization of LEQEMBI for the treatment of Alzheimer's disease and [removed: Sage] [added: 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 [removed: CLL and] [added: CLL,] follicular [removed: lymphoma;] [added: lymphoma and, following its approval in October 2025, lupus nephritis;] OCREVUS for the treatment of PPMS and RMS; LUNSUMIO for the treatment of relapsed or refractory follicular lymphoma; COLUMVI, a bispecific antibody for the treatment of non-Hodgkin's lymphoma; and have the option to add other potential anti-CD20 therapies, pursuant to our collaboration arrangements with Genentech, a [removed: wholly-owned] [added: wholly owned] member of the Roche Group.

We commercialize a portfolio of biosimilars of advanced biologics including: BENEPALI, an etanercept biosimilar referencing ENBREL; IMRALDI, an adalimumab biosimilar referencing HUMIRA; [added: and] FLIXABI, an infliximab biosimilar referencing [removed: 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.][added: REMICADE.]

For additional information on our acquisition of [removed: HI-Bio,] [added: Alcyone,] please read *Note 2, [removed: Acquisitions*,] [added: Acquisitions,*] to our consolidated financial statements included in this report.

[added: The] Solothurn [added: facility is operational and] has been approved for the manufacture of [removed: LEQEMBI.][added: LEQEMBI and TYSABRI.]

We expect the future sales of TYSABRI [removed: may] [added: will continue to] be adversely affected by the entrance of this biosimilar.

Global disputes and interruptions in international relationships, including tariffs, trade protection measures, [added: embargoes,] import or export licensing requirements and the imposition of trade sanctions or similar restrictions, [added: may] affect our ability to do [removed: business.][added: business and the costs that we incur in providing products to our patients.]

[removed: For example, tensions between China and Taiwan and] [added: Trade-related] tensions between the U.S. and China have led to a series of tariffs and sanctions being imposed by the U.S. on imports from China [removed: mainland,] [added: and] retaliatory tariffs imposed by China on U.S. [removed: imports, as well as other business restrictions, with additional restrictive measures being proposed.][added: imports.]

Engaging alternative suppliers may involve seeking additional regulatory approvals and [removed: be costly in terms of time] [added: incurring additional costs] and [removed: resources needed.][added: risks associated with new suppliers.]

The ongoing geopolitical tensions related to Russia's invasion of Ukraine and the military conflict in the Middle East [added: and other global geopolitical developments] have resulted in global business disruptions and economic volatility.

Although we do not have affiliates or [removed: employees,] [added: employees] in either Russia or Ukraine, we do provide various therapies to patients in Russia through a distributor.

[removed: In addition, new government] [added: Government] sanctions on the export of certain manufacturing materials to Russia may delay or limit our ability to get new products approved.

We will continue to monitor the ongoing conflict between Russia and Ukraine as well as the military conflict in the Middle East and [added: other global geopolitical developments and] assess any potential impacts on our business, supply chain, partners or customers, as well as any factors that could have an adverse effect on our results of operations.

Revenue generated from sales in Russia and Ukraine represent less than 2.0% of total revenue for the years ended December 31, [removed: 2024, 2023] [added: 2025, 2024] and [removed: 2022.][added: 2023.]

Additionally, revenue generated from sales in the broader Middle East region represents less than 2.0% of total revenue for the years ended December 31, [removed: 2024, 2023] [added: 2025, 2024] and [removed: 2022.][added: 2023.]

The IRA did not result in any material adjustments to our income tax provision or other income tax balances as of December 31, [removed: 2024] [added: 2025] and [removed: 2023.][added: 2024.]

[removed: We expect the] [added: The] IRA's drug pricing controls and Medicare Part D redesign [removed: may have] [added: had] an adverse impact on our sales, particularly for our products that are more substantially reliant on Medicare reimbursement.

[removed: We anticipate the IRA Medicare Part D redesign will have a] modest net unfavorable impact to our 2025 [removed: revenue, ranging from] [added: revenue of] approximately [removed: $50.0 million to $100.0] [added: $90.0] million, concentrated in our SKYCLARYS and MS portfolio product revenue, approximately a [removed: third] [added: quarter] of which [removed: could be] [added: was] associated with SKYCLARYS.

The degree of impact from this legislation on our business depends on a number of forthcoming implementation actions by regulatory authorities, [added: which may be further impacted by other legislative acts that may modify or replace] the [removed: full extent of] [added: IRA, such as] the [removed: IRA's impacts on our sales and, in turn, our business, remains unclear.][added: OBBBA.]

As described below under *Results of Operations*, our net income and diluted earnings per share attributable to Biogen Inc. for the year ended December 31, [removed: 2024,] [added: 2025,] compared to the year ended December 31, [removed: 2023,] [added: 2024,] reflects the following:

[removed: ][added: ]

[removed: ][added: ]

[removed: ][added: ]

- MS revenue decreased [removed: $312.1] [added: $310.9] million, or [removed: 6.7%][added: 7.1%]

- Rare disease revenue increased [removed: $185.1] [added: $166.1] million, or [removed: 10.3%][added: 8.4%]

- The increase in rare disease product revenue [removed: in 2024] was primarily due to [removed: revenue from] [added: our] new product launches, including global SKYCLARYS revenue of [removed: $382.5 million, $72.2] [added: $520.5] million [removed: for ZURZUVAE] and [removed: $32.4] [added: global QALSODY revenue of $86.9] million [removed: for QALSODY.][added: in 2025.]

[removed: ][added: ]

- R&D expense decreased [removed: $420.2] [added: $201.7] million, or [removed: 17.1%][added: 10.2%]

[removed: - Amortization and impairment of acquired intangible assets increased $206.1 million, or 85.7%][added: COST OF SALES, EXCLUDING AMORTIZATION AND IMPAIRMENT OF ACQUIRED INTANGIBLE ASSETS]

[removed: - The] [added: For 2025 compared to 2024, the] decrease in [added: product] cost of sales was primarily due to [removed: favorable product mix from] lower [added: inventory write-offs, partially offset by product mix, including higher] contract manufacturing revenue [removed: and lower idle capacity charges, partially offset] [added: driven] by [removed: approximately $181.5 million in] [added: the timing of batch releases and higher] SKYCLARYS [added: inventory step-up] amortization costs.

[removed: - The] [added: For 2025 compared to 2024, the] decrease in [removed: R&D expense] [added: research and development] was primarily driven by [removed: approximately $197.0 million of equity-based compensation expense recognized in 2023 related to our Reata acquisition,] [added: continued] cost-reduction measures realized in [removed: 2024 in] connection with our portfolio prioritization initiatives and our Fit for Growth program, [removed: as well as higher spend on clinical trials and close out costs incurred during 2023, partially offset by] approximately [added: $23.9 million of step-up amortization related to SKYCLARYS inventory recorded in 2025, compared to] $48.5 million in [removed: SKYCLARYS amortization costs] [added: 2024,] and approximately $42.5 million of equity-based compensation expense recognized in 2024 related to our [removed: HI-Bio acquisition.][added: acquisition of HI-Bio.]

[removed: -] The increase in amortization [removed: and impairment] of acquired intangible [removed: assets] [added: assets, excluding impairment charges,] was primarily due to amortization for the acquired intangible assets associated with [removed: SKYCLARYS, as well as impairment charges of approximately $60.2 million during 2024.][added: SKYCLARYS and TYSABRI.]

- [removed: Cash and] [added: Cash,] cash equivalents [added: and marketable securities] totaled approximately [removed: $2.4] [added: $4.2] billion as of December 31, [removed: 2024,] [added: 2025,] compared to approximately [removed: $1.0] [added: $2.4] billion as of December 31, [removed: 2023.][added: 2024.]

[removed: - We generated approximately $2,875.5 million of net cash flow from operations for] [added: For] the year ended December 31, [added: 2025, net interest expense was approximately $142.5 million, compared to net interest expense of $182.7 million in] 2024.

For additional information on our acquisition of [removed: HI-Bio,] [added: Alcyone,] please read *Note 2, [removed: Acquisitions*,] [added: Acquisitions,*] to our consolidated financial statements included in this report.

[removed: SALE OF PRIORITY REVIEW VOUCHER][added: | Gain on sale of priority review voucher, net | | | | | | — | | | | | | (88.6) | | | | | | — | | | | | | nm | | | | | | nm | | | | | | 88.6 | | | | | | (88.6) | | |]

For additional information on [removed: the] [added: our] sale of [removed: our PRV,] [added: TOFIDENCE,] please read *Note 3, Dispositions*, to our consolidated financial statements included in this report.

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.

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.

GOODWILL

We review our goodwill for impairment annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of the goodwill may not be recoverable.

As part of this analysis, we compare the fair value of our one reporting unit to its carrying value through the assessment of qualitative, and, if necessary, quantitative factors.

If the carrying value of the net assets assigned to the reporting unit exceeds the fair value of our reporting unit, we will record an impairment loss equal to the difference.

As of our most recent annual impairment analysis, we had no accumulated impairment losses related to goodwill.

An interim goodwill impairment test based on quantitative factors may be required if adverse events indicate an impairment might be present.

We monitor changes to our stock price between annual impairment tests, and we believe that general deterioration in macroeconomic and industry-specific conditions may not be indicators of a goodwill impairment, as such conditions may not represent a significant adverse change to our underlying operating performance, cash flows, financial condition or liquidity.

Should our market capitalization decline below the carrying value of our net assets for a sustained period, we would consider the length and severity of the decline and the reason for the decline when assessing whether potential goodwill impairment exists.

INTERNATIONAL TRADE

The U.S. has imposed a baseline tariff on imports from all countries, subject to certain exceptions.

The U.S. Secretary of Commerce has further initiated an investigation to determine the effects on the national security of imports of pharmaceuticals and pharmaceutical ingredients, including finished drug products, medical countermeasures, critical inputs such as active pharmaceutical ingredients, key starting materials and derivative products of those items, under Section 232 of the Trade Expansion Act of 1962.

There is a high degree of uncertainty concerning what future steps countries and economic blocs will take in response to changes in global trade rules and economics.

We have a significant manufacturing presence in the U.S. While our portfolio is evolving, approximately three quarters of our 2025 U.S. product revenue was attributable to products which were largely manufactured in the U.S. However, we, and the pharmaceutical industry, do utilize partners and production facilities located outside the U.S. for certain raw materials, ingredients, processes and components for our pharmaceutical products and their delivery devices.

This may be costly in terms of time and resources needed or result in delays.

Key products that are currently manufactured mainly outside the U.S. are TECFIDERA, VUMERITY and LEQEMBI.

In 2024 we initiated a technology transfer process to enable us to manufacture LEQEMBI in the U.S., which was approved in January 2026.

Although certain starting materials for SKYCLARYS rely on a single supplier based in China, the manufacturing process, including active pharmaceutical ingredients and drug substance, is primarily conducted in the U.S.

We are working to mitigate potential exposure from tariffs across our network.

As of the date of this filing, we do not expect the tariffs currently applicable to our business to result in a material adverse effect on our operations in 2026.

This is based on existing tariffs either in place or potential tariffs as previously announced by the U.S. Administration, our manufacturing footprint, and our inventory levels and positioning.

Should significant additional tariffs be enacted, our business could be impacted in the future and differ materially from our current expectations.

We will continue to monitor the current and future global tariff landscape as it evolves.

FACTORS AFFECTING PHARMACEUTICAL PRICING AND OTHER DEVELOPMENTS

The IRA Medicare Part D redesign had a

The degree of impact from this legislation on our business depends on a number of forthcoming implementation actions by regulatory authorities, which may be further impacted by other legislative acts that may modify or replace the IRA, such as the OBBBA, as discussed below.

The full extent of the IRA's impacts on our sales and, in turn, our business, remains uncertain.

Additionally, in May 2025 the U.S. government issued an executive order aiming to establish an MFN drug pricing policy that would tie U.S. drug prices to the prices paid for drugs in other developed countries.

If HHS sets MFN pricing targets for prescription drugs, including the use of international reference pricing to set drug prices in the U.S., it could result in reduced prices and reimbursement for certain of the Company's products in the U.S. We continue to evaluate the potential impact of this executive order.

This executive order and any additional legislation, regulations or initiatives related to drug pricing, such as the CMS-proposed MFN initiatives, the Global Benchmark for Efficient Drug Pricing for certain Medicare Part B drugs and the Guarding U.S. Medicare Against Rising Drug Costs for certain Medicare Part D drugs, could create additional uncertainty around the timing and prioritization around worldwide commercial efforts and adversely impact our business and results of operations.

2025 LEGISLATION AND TAX REFORM

On July 4, 2025, the U.S. signed into law the H.R.1 legislation formally titled "An Act to Provide for Reconciliation Pursuant to Title II of H.

Con.

Res.

14", commonly referred to as the OBBBA.

The OBBBA contains tax provisions, such as the permanent extension or revision of certain expiring provisions of the Tax Cuts and Jobs Act enacted in 2017, modifications to the international tax framework and the restoration of favorable tax treatment for certain business provisions.

The provisions of the OBBBA have multiple effective dates, with certain provisions effective in 2025 and others implemented through 2027.

The OBBBA did not result in any material adjustments to our total income tax provision for the year ended December 31, 2025, and we have adjusted our deferred tax balances to reflect the impacts of the OBBBA enactment.

However, given the complexity of tax laws, related regulations and interpretations, our current estimates may require revision as additional information becomes available regarding the application of the OBBBA provisions.

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.

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.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

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.

BUSINESS UPDATE REGARDING MACROECONOMIC CONDITIONS AND OTHER DISRUPTIONS

Significant portions of our business are conducted in Europe, Asia and other international geographies.

Factors such as global health outbreaks, adverse weather events, geopolitical events, tariffs, inflation, labor or raw material shortages and other supply chain disruptions could result in product shortages or other difficulties and delays or increased costs in manufacturing our products.

CURRENT ECONOMIC CONDITIONS

Economic conditions remain vulnerable as markets continue to be impacted in part by elevated inflation, higher interest rates, adverse weather events, global supply chain uncertainties and risks associated with geopolitical conflicts.

ADVERSE WEATHER EVENTS

Adverse weather conditions, including hurricanes, earthquakes, wildfires and natural disaster damage, may affect our ability to do business.

We currently have operations in RTP, North Carolina, which were not impacted by recent hurricanes.

GLOBAL SUPPLY CHAIN DISRUPTIONS

Global supply chain disruptions, such as strikes, work stoppages, port congestion, port closures and other logistical problems, may affect our ability to do business.

For example, in 2024 major port strikes on the East and Gulf Coasts of the U.S. resulted in delayed cargo movement for several days.

As our primary shipping method for resources and finished goods is through air freight, the recent port strikes did not impact our business; however, we will continue to assess any future port disruptions and if necessary, work to secure alternative transportation.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

We, and the pharmaceutical industry, utilize China-based partners for certain raw materials, ingredients and components for our pharmaceutical products and their delivery devices.

For example, certain early processes related to our acquired SKYCLARYS product rely on a single supplier based in China.

We are continuing to evaluate SKYCLARYS' supply chain and prioritizing actions to mitigate risks associated with its manufacturing and our ability to supply patients.

INFLATION REDUCTION ACT OF 2022

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

Decreased

$159.7 million or 1.6%

$3.21 or 40.3%

$33.2 million or 0.5%

- The decrease in MS product revenue was primarily due to a decrease in Interferon demand due to competition as patients transition to higher efficacy therapies and a decrease in global TYSABRI revenue driven by increased competition.

This was partially offset by a decrease in rest of world SPINRAZA revenue driven by the loss of an annual tender in Russia which resulted in an unfavorable impact of approximately $45.0 million.

The decrease was also impacted by the timing of SPINRAZA shipments and the unfavorable impact of foreign currency exchange.

$768.9 million or 9.0%

- Cost of sales decreased $223.0 million, or 8.8%

- SG&A expense decreased $146.0 million, or 5.7%

- The decrease in SG&A expense was primarily due to approximately $196.4 million of equity-based compensation expense recognized in 2023 related to our Reata acquisition.

- We received a net cash payment of $88.6 million from the sale of our rare pediatric disease PRV in 2024.

- In April 2024 we received $437.5 million from Samsung BioLogics related to the sale of our equity interest in Samsung Bioepis.

- In July 2024 we completed the acquisition of HI-Bio for $1.15 billion, which was funded through available cash on hand.

As a result, our consolidated financial position, results of operations and cash flow can be affected by market fluctuations in foreign currency exchange rates, primarily with respect to the Euro, British pound sterling, Canadian [removed: dollar and] [added: dollar,] Swiss [removed: franc.][added: franc and the Polish złoty.]

This categorization did not have a material impact on our results of operations or financial position as of December 31, [removed: 2024,] [added: 2025,] and is not expected to have a material impact on our results of operations or financial position in the future.

We use foreign currency forward contracts and foreign currency options to manage foreign currency risk, with the majority of our forward contracts and options used to hedge certain forecasted revenue and operating expense transactions denominated in foreign currencies in the next [removed: 12] [added: 21] months.

In these instances, we principally utilize [removed: currency forward contracts.]

As of December 31, [removed: 2024] [added: 2025] and [removed: 2023,] [added: 2024,] a hypothetical adverse 10.0% movement in foreign currency exchange rates compared to the U.S. dollar across all maturities would result in a hypothetical decrease in the fair value of forward contracts of approximately [removed: $191.7] [added: $278.0] million and [removed: $249.4] [added: $191.7] million, respectively.

Our use of this methodology to quantify the market risk of such instruments is subject to assumptions and [added: the] actual impact could be significantly [added: different.]

We believe that our allowance for doubtful accounts was adequate as of December 31, [removed: 2024] [added: 2025] and [removed: 2023.][added: 2024.]

currency forward contracts.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

In December 2023 the Argentinian Peso experienced a substantial devaluation following a presidential election.

The devaluation resulted in a $16.0 million charge recorded during the fourth quarter of 2023 in other (income) expense, net within our consolidated statements of income for the year ended December 31, 2023.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

different.

EQUITY PRICE RISK

Our strategic investment portfolio includes investments in equity securities of certain biotechnology companies.

While we are holding such securities, we are subject to equity price risk, and this may increase the volatility of our income in future periods due to changes in the fair value of equity investments.

We may sell such equity securities based on our business considerations, which may include limiting our price risk.

Changes in the fair value of these equity securities are impacted by the volatility of the stock market and changes in general economic conditions, among other factors.

The potential change in fair value for equity price sensitive instruments has been assessed on a hypothetical 10.0% adverse movement.

As of December 31, 2024 and 2023, a hypothetical adverse 10.0% movement would result in a hypothetical decrease in fair value of approximately $18.0 million and $41.7 million, respectively.

[removed: OVERVIEW][added: OVERVIEW]

We market the first and only drug approved in the [removed: U.S. and] [added: U.S.,] the E.U. [added: and certain international markets] for the treatment of FA in adults and adolescents aged 16 years and older.

Our marketed products include [removed: TECFIDERA,] VUMERITY, [removed: AVONEX, PLEGRIDY] [added: TYSABRI, TECFIDERA, AVONEX] and [removed: TYSABRI] [added: PLEGRIDY] for the treatment of MS; SPINRAZA for the treatment of SMA; SKYCLARYS for the treatment of FA; [removed: QALSODY for the treatment of ALS;] and [removed: FUMADERM] [added: QALSODY] for the treatment of [removed: severe plaque psoriasis.][added: ALS.]

We also have collaborations with Eisai on the commercialization of LEQEMBI for the treatment of Alzheimer's disease and [removed: Sage] [added: 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 [removed: CLL and] [added: CLL,] follicular [removed: lymphoma;] [added: lymphoma and, following its approval in October 2025, lupus nephritis;] OCREVUS for the treatment of PPMS and RMS; LUNSUMIO for the treatment of relapsed or refractory follicular lymphoma; COLUMVI, a bispecific antibody for the treatment of non-Hodgkin's lymphoma; and have the option to add other potential anti-CD20 therapies, pursuant to our collaboration arrangements with Genentech, a [removed: wholly-owned] [added: wholly owned] member of the Roche Group.

We commercialize a portfolio of biosimilars of advanced biologics including: BENEPALI, an etanercept biosimilar referencing ENBREL; IMRALDI, an adalimumab biosimilar referencing HUMIRA; [added: and] FLIXABI, an infliximab biosimilar referencing [removed: 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.][added: REMICADE.]

For additional information on our acquisition of [removed: HI-Bio,] [added: Alcyone,] please read *Note 2, [removed: Acquisitions*,] [added: Acquisitions,*] to our consolidated financial statements included in this report.

The following is a summary of key developments affecting our business since the beginning of [removed: 2024.][added: 2025.]

For additional information on our [removed: acquisition of HI-Bio,] [added: lease agreement,] please read *Note [removed: 2, Acquisitions*,] [added: 12, Leases,*] to our consolidated financial statements included in this report.

For additional information on [removed: the] [added: our] sale of [removed: our PRV,] [added: TOFIDENCE,] please read *Note 3, Dispositions*, to our consolidated financial statements included in this report.

[removed: DEVELOPMENTS] [added: DEVELOPMENTS] IN KEY COLLABORATIVE [removed: RELATIONSHIPS][added: RELATIONSHIPS]

For additional information on our [removed: collaborative and other relationships discussed below,] [added: research arrangement with Dayra,] please read *Note 19, Collaborative and Other Relationships,* to our consolidated financial statements included in this report.

[removed: LEQEMBI (lecanemab)][added: LEQEMBI (lecanemab)]

- In January [removed: 2025] [added: 2026] the FDA accepted for review the [added: supplemental] BLA for LEQEMBI subcutaneous [removed: autoinjector] [added: autoinjector, LEQEMBI IQLIK,] for weekly [removed: maintenance dosing,] [added: starting dose,] with a PDUFA action date [removed: set for August 31, 2025.][added: of May 24, 2026.]

[removed: McDonnell,] [added: | Robin C. Kramer | | | | | |] Executive Vice President and Chief Financial [removed: Officer, plans to retire from Biogen on March 1, 2025.][added: Officer | | | | | | 60 | | | | | | 2018 | | |]

[removed: Kramer, currently Senior Vice President and Chief Accounting Officer at Biogen, will assume the role of] [added: Kramer became] Executive Vice President and Chief Financial Officer.

- In [removed: January] [added: March] 2025 [removed: we announced the appointment of] Sean Godbout [removed: as] [added: became] Vice President, Chief Accounting Officer and Global Corporate [removed: Controller, effective March 1, 2025, upon the transition of Robin C.][added: Controller.]

[removed: *•*In January] [added: - In September] 2025 the FDA [removed: accepted] [added: issued a CRL for] the supplemental NDA [removed: and the EMA validated the application] for a higher dose regimen of nusinersen for [added: the treatment of] SMA.

SKYCLARYS [added: (omaveloxolone)]

- In [removed: May 2024 the EC approved] [added: March 2025 Health Canada issued marketing authorization with conditions for] QALSODY [removed: in the E.U.] for the treatment of [removed: adults with] ALS [removed: associated with] [added: in adults who have] a mutation in the SOD1 gene.

[removed: *zuranolone*][added: ZURZUVAE (zuranolone)]

[removed: In] [added: Effective] January [removed: 2024 we notified Acorda of our decision to terminate] [added: 1, 2025,] our collaboration and license [removed: agreement, effective January 1, 2025, whereby Acorda regained] [added: agreement for FAMPYRA] global commercialization rights [removed: to FAMPYRA.][added: was terminated.]

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

The following graph shows our product revenue, revenue from anti-CD20 therapeutic programs and Alzheimer's collaboration revenue for the years ended December 31, [removed: 2024, 2023] [added: 2025, 2024] and [removed: 2022.][added: 2023.]

[removed: ][added: ]

(2) Rare disease includes SPINRAZA, QALSODY, which became commercially available in the [removed: U.S.] [added: E.U.] during the second quarter of [removed: 2023] [added: 2024,] and [added: SKYCLARYS which became] commercially available in the E.U. during the [removed: second] [added: first] quarter of [removed: 2024, and SKYCLARYS, which was obtained as part of our acquisition of Reata in September 2023.][added: 2024.]

[removed: SKYCLARYS was approved] [added: Rare disease includes SPINRAZA for SMA, QALSODY for ALS, which became commercially available in the E.U. during the second quarter of 2024,] and [added: SKYCLARYS for FA, which] became commercially available in the E.U. during the first quarter of 2024.

(5) Anti-CD20 therapeutic programs include RITUXAN, RITUXAN HYCELA, GAZYVA, OCREVUS and [removed: LUNSUMIO, which became commercially available in the U.S. during the first quarter of 2023.][added: LUNSUMIO.]

Product sales for [removed: TECFIDERA,] TYSABRI and SPINRAZA each accounted for more than 10.0% of our total revenue for the years ended December 31, [removed: 2024, 2023] [added: 2025, 2024] and [removed: 2022.][added: 2023.]

| [removed: ] [added: ] | | | | | | RMS RRMS in the E.U. Crohn's disease in the U.S. | | | | | | None | | | | | | U.S. Brazil France Germany Italy U.K. | | |

| [removed: ] [added: ] | | | | | | RMS in the U.S. RRMS in the E.U. | | | | | | None | | | | | | U.S. France Germany Italy Japan [removed: U.K.] [added: Poland] | | |

| [removed: ] [added: ] | | | | | | RMS in the U.S. RRMS in the E.U. | | | | | | [removed: Alkermes Pharma Ireland Limited, a subsidiary of Alkermes] [added: None] | | | | | | U.S. France Germany [removed: Netherlands] Spain Switzerland [added: U.K.] | | |

| [removed: ] [added: ] | | | | | | RMS | | | | | | None | | | | | | U.S. Canada France Germany Italy Spain | | |

| [removed: ] [added: ] | | | | | | RMS in the U.S. RRMS in the E.U. | | | | | | None | | | | | | U.S. France Germany Italy [added: Russia] Spain U.K. | | |

For additional information on our collaboration arrangements with [removed: Alkermes,] [added: Supernus,] please read *Note 19, Collaborative and Other Relationships,* to our consolidated financial statements included in this report.

| [removed: ] [added: ] | | | | | | Alzheimer's disease | | | | | | Eisai | | | | | | U.S. China [removed: Great Britain Israel] Japan South Korea [removed: United Arab Emirates] | | |

| [removed: ] [added: ] | | | | | | PPD in adults | | | | | | [removed: Sage] [added: Supernus] | | | | | | U.S. | | |

For additional information on our collaboration [removed: arrangements] [added: arrangement] with [removed: Sage,] [added: Stoke,] please read *Note 19, Collaborative and Other Relationships,* to our consolidated financial statements included in this report.

| [removed: ] [added: ] | | | | | | SMA | | | | | | Ionis | | | | | | U.S. Brazil France Germany Italy [removed: Turkey] [added: Poland] | | |

| [removed: ] [added: ] | | | | | | FA in adults and adolescents aged 16 years and older | | | | | | None | | | | | | U.S. France Germany [added: Greece Italy Turkey] | | |

ACQUISITIONS

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.

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

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.

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.

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 expense of $200.0 million within our consolidated statements of income.

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.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

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.

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.

- 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.

- 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.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

- 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 October 2024 we announced that Michael R.

Upon Mr. McDonnell's retirement, 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.

Minor, M.D. joined our Board of Directors.

- Effective January 1, 2025, Sir Menelas (Mene) Pangalos, Ph.D. joined our Board of Directors.

For a discussion of legal matters as of December 31, [removed: 2024,] [added: 2025,] please read *Note 21, Litigation,* to our consolidated financial statements included in this report, which is incorporated into this item by reference.

For the fiscal year ended December 31, [removed: 2024][added: 2025]

[removed: ][added: ]

The aggregate market value of the registrant’s common stock held by non-affiliates of the registrant (without admitting that any person whose shares are not included in such calculation is an affiliate) computed by reference to the price at which the common stock was last sold as of the last business day of the registrant’s most recently completed second fiscal quarter was [removed: $33,709,755,067.][added: $18,378,285,308.]

As of February [removed: 11, 2025,] [added: 4, 2026,] the registrant had [removed: 146,374,937] [added: 146,758,528] shares of common stock, $0.0005 par value, outstanding.

Portions of the definitive proxy statement for our [removed: 2025] [added: 2026] Annual Meeting of Stockholders are incorporated by reference into Part III of this report.

For the Year Ended December 31, [removed: 2024][added: 2025]

| [Item [removed: 1.](#i8f04c147560c48a7bb5358179696a625_28)] [added: 1.](#i2dd641cc643b4c5aaf649d4cde640538_28)] | | | [removed: [Business](#i8f04c147560c48a7bb5358179696a625_28)] [added: [Business](#i2dd641cc643b4c5aaf649d4cde640538_28)] | | | [removed: [1](#i8f04c147560c48a7bb5358179696a625_28)] [added: [1](#i2dd641cc643b4c5aaf649d4cde640538_28)] | | |

| [Item [removed: 1A.](#i8f04c147560c48a7bb5358179696a625_73)] [added: 1A.](#i2dd641cc643b4c5aaf649d4cde640538_76)] | | | [Risk [removed: Factors](#i8f04c147560c48a7bb5358179696a625_73)] [added: Factors](#i2dd641cc643b4c5aaf649d4cde640538_76)] | | | [removed: [38](#i8f04c147560c48a7bb5358179696a625_73)] [added: [39](#i2dd641cc643b4c5aaf649d4cde640538_76)] | | |

| [Item [removed: 1B.](#i8f04c147560c48a7bb5358179696a625_76)] [added: 1B.](#i2dd641cc643b4c5aaf649d4cde640538_79)] | | | [Unresolved Staff [removed: Comments](#i8f04c147560c48a7bb5358179696a625_76)] [added: Comments](#i2dd641cc643b4c5aaf649d4cde640538_79)] | | | [removed: [52](#i8f04c147560c48a7bb5358179696a625_76)] [added: [54](#i2dd641cc643b4c5aaf649d4cde640538_79)] | | |

| [Item [removed: 1C.](#i8f04c147560c48a7bb5358179696a625_79)] [added: 1C.](#i2dd641cc643b4c5aaf649d4cde640538_82)] | | | [removed: [Cybersecurity](#i8f04c147560c48a7bb5358179696a625_79)] [added: [Cybersecurity](#i2dd641cc643b4c5aaf649d4cde640538_82)] | | | [removed: [52](#i8f04c147560c48a7bb5358179696a625_79)] [added: [54](#i2dd641cc643b4c5aaf649d4cde640538_82)] | | |

| [Item [removed: 2.](#i8f04c147560c48a7bb5358179696a625_82)] [added: 2.](#i2dd641cc643b4c5aaf649d4cde640538_85)] | | | [removed: [Properties](#i8f04c147560c48a7bb5358179696a625_82)] [added: [Properties](#i2dd641cc643b4c5aaf649d4cde640538_85)] | | | [removed: [54](#i8f04c147560c48a7bb5358179696a625_82)] [added: [55](#i2dd641cc643b4c5aaf649d4cde640538_85)] | | |

| [Item [removed: 3.](#i8f04c147560c48a7bb5358179696a625_85)] [added: 3.](#i2dd641cc643b4c5aaf649d4cde640538_91)] | | | [Legal [removed: Proceedings](#i8f04c147560c48a7bb5358179696a625_85)] [added: Proceedings](#i2dd641cc643b4c5aaf649d4cde640538_91)] | | | [removed: [54](#i8f04c147560c48a7bb5358179696a625_85)] [added: [56](#i2dd641cc643b4c5aaf649d4cde640538_91)] | | |

| [Item [removed: 4.](#i8f04c147560c48a7bb5358179696a625_88)] [added: 4.](#i2dd641cc643b4c5aaf649d4cde640538_94)] | | | [Mine Safety [removed: Disclosures](#i8f04c147560c48a7bb5358179696a625_88)] [added: Disclosures](#i2dd641cc643b4c5aaf649d4cde640538_94)] | | | [removed: [54](#i8f04c147560c48a7bb5358179696a625_88)] [added: [56](#i2dd641cc643b4c5aaf649d4cde640538_94)] | | |

| [Item [removed: 5.](#i8f04c147560c48a7bb5358179696a625_94)] [added: 5.](#i2dd641cc643b4c5aaf649d4cde640538_100)] | | | [Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity [removed: Securities](#i8f04c147560c48a7bb5358179696a625_94)] [added: Securities](#i2dd641cc643b4c5aaf649d4cde640538_100)] | | | [removed: [55](#i8f04c147560c48a7bb5358179696a625_94)] [added: [57](#i2dd641cc643b4c5aaf649d4cde640538_100)] | | |

| [Item [removed: 6.](#i8f04c147560c48a7bb5358179696a625_97)] [added: 6.](#i2dd641cc643b4c5aaf649d4cde640538_103)] | | | [removed: [Reserved](#i8f04c147560c48a7bb5358179696a625_97)] [added: [Reserved](#i2dd641cc643b4c5aaf649d4cde640538_103)] | | | [removed: [56](#i8f04c147560c48a7bb5358179696a625_97)] [added: [58](#i2dd641cc643b4c5aaf649d4cde640538_103)] | | |

| [Item [removed: 7.](#i8f04c147560c48a7bb5358179696a625_100)] [added: 7.](#i2dd641cc643b4c5aaf649d4cde640538_106)] | | | [Management’s Discussion and Analysis of Financial Condition and Results of [removed: Operations](#i8f04c147560c48a7bb5358179696a625_100)] [added: Operations](#i2dd641cc643b4c5aaf649d4cde640538_106)] | | | [removed: [57](#i8f04c147560c48a7bb5358179696a625_100)] [added: [59](#i2dd641cc643b4c5aaf649d4cde640538_106)] | | |

| [Item [removed: 7A.](#i8f04c147560c48a7bb5358179696a625_232)] [added: 7A.](#i2dd641cc643b4c5aaf649d4cde640538_235)] | | | [Quantitative and Qualitative Disclosures About Market [removed: Risk](#i8f04c147560c48a7bb5358179696a625_232)] [added: Risk](#i2dd641cc643b4c5aaf649d4cde640538_235)] | | | [removed: [87](#i8f04c147560c48a7bb5358179696a625_232)] [added: [93](#i2dd641cc643b4c5aaf649d4cde640538_235)] | | |

| [Item [removed: 8.](#i8f04c147560c48a7bb5358179696a625_235)] [added: 8.](#i2dd641cc643b4c5aaf649d4cde640538_238)] | | | [Financial Statements and Supplementary [removed: Data](#i8f04c147560c48a7bb5358179696a625_235)] [added: Data](#i2dd641cc643b4c5aaf649d4cde640538_238)] | | | [removed: [89](#i8f04c147560c48a7bb5358179696a625_235)] [added: [94](#i2dd641cc643b4c5aaf649d4cde640538_238)] | | |

| [Item [removed: 9.](#i8f04c147560c48a7bb5358179696a625_238)] [added: 9.](#i2dd641cc643b4c5aaf649d4cde640538_241)] | | | [Changes in and Disagreements with Accountants on Accounting and Financial [removed: Disclosure](#i8f04c147560c48a7bb5358179696a625_238)] [added: Disclosure](#i2dd641cc643b4c5aaf649d4cde640538_241)] | | | [removed: [89](#i8f04c147560c48a7bb5358179696a625_238)] [added: [94](#i2dd641cc643b4c5aaf649d4cde640538_241)] | | |

| [Item [removed: 9A.](#i8f04c147560c48a7bb5358179696a625_241)] [added: 9A.](#i2dd641cc643b4c5aaf649d4cde640538_244)] | | | [Controls and [removed: Procedures](#i8f04c147560c48a7bb5358179696a625_241)] [added: Procedures](#i2dd641cc643b4c5aaf649d4cde640538_244)] | | | [removed: [89](#i8f04c147560c48a7bb5358179696a625_241)] [added: [94](#i2dd641cc643b4c5aaf649d4cde640538_244)] | | |

| [Item [removed: 9B.](#i8f04c147560c48a7bb5358179696a625_244)] [added: 9B.](#i2dd641cc643b4c5aaf649d4cde640538_247)] | | | [Other [removed: Information](#i8f04c147560c48a7bb5358179696a625_244)] [added: Information](#i2dd641cc643b4c5aaf649d4cde640538_247)] | | | [removed: [90](#i8f04c147560c48a7bb5358179696a625_244)] [added: [95](#i2dd641cc643b4c5aaf649d4cde640538_247)] | | |

| [Item [removed: 9C.](#i8f04c147560c48a7bb5358179696a625_250)] [added: 9C.](#i2dd641cc643b4c5aaf649d4cde640538_253)] | | | [Disclosure Regarding Foreign Jurisdictions that Prevent [removed: Inspections](#i8f04c147560c48a7bb5358179696a625_250)] [added: Inspections](#i2dd641cc643b4c5aaf649d4cde640538_253)] | | | [removed: [91](#i8f04c147560c48a7bb5358179696a625_250)] [added: [95](#i2dd641cc643b4c5aaf649d4cde640538_253)] | | |

| [Item [removed: 10.](#i8f04c147560c48a7bb5358179696a625_256)] [added: 10.](#i2dd641cc643b4c5aaf649d4cde640538_259)] | | | [Directors, Executive Officers and Corporate [removed: Governance](#i8f04c147560c48a7bb5358179696a625_256)] [added: Governance](#i2dd641cc643b4c5aaf649d4cde640538_259)] | | | [removed: [92](#i8f04c147560c48a7bb5358179696a625_256)] [added: [96](#i2dd641cc643b4c5aaf649d4cde640538_259)] | | |

| [Item [removed: 11.](#i8f04c147560c48a7bb5358179696a625_259)] [added: 11.](#i2dd641cc643b4c5aaf649d4cde640538_262)] | | | [Executive [removed: Compensation](#i8f04c147560c48a7bb5358179696a625_259)] [added: Compensation](#i2dd641cc643b4c5aaf649d4cde640538_262)] | | | [removed: [92](#i8f04c147560c48a7bb5358179696a625_259)] [added: [96](#i2dd641cc643b4c5aaf649d4cde640538_262)] | | |

| [Item [removed: 12.](#i8f04c147560c48a7bb5358179696a625_262)] [added: 12.](#i2dd641cc643b4c5aaf649d4cde640538_265)] | | | [Security Ownership of Certain Beneficial Owners and Management and Related Stockholder [removed: Matters](#i8f04c147560c48a7bb5358179696a625_262)] [added: Matters](#i2dd641cc643b4c5aaf649d4cde640538_265)] | | | [removed: [92](#i8f04c147560c48a7bb5358179696a625_262)] [added: [96](#i2dd641cc643b4c5aaf649d4cde640538_265)] | | |

| [Item [removed: 13.](#i8f04c147560c48a7bb5358179696a625_265)] [added: 13.](#i2dd641cc643b4c5aaf649d4cde640538_268)] | | | [Certain Relationships and Related Transactions, and Director [removed: Independence](#i8f04c147560c48a7bb5358179696a625_265)] [added: Independence](#i2dd641cc643b4c5aaf649d4cde640538_268)] | | | [removed: [92](#i8f04c147560c48a7bb5358179696a625_265)] [added: [96](#i2dd641cc643b4c5aaf649d4cde640538_268)] | | |

| [Item [removed: 14.](#i8f04c147560c48a7bb5358179696a625_268)] [added: 14.](#i2dd641cc643b4c5aaf649d4cde640538_271)] | | | [Principal Accountant Fees and [removed: Services](#i8f04c147560c48a7bb5358179696a625_268)] [added: Services](#i2dd641cc643b4c5aaf649d4cde640538_271)] | | | [removed: [92](#i8f04c147560c48a7bb5358179696a625_268)] [added: [96](#i2dd641cc643b4c5aaf649d4cde640538_271)] | | |

| [Item [removed: 15.](#i8f04c147560c48a7bb5358179696a625_274)] [added: 15.](#i2dd641cc643b4c5aaf649d4cde640538_277)] | | | [Exhibits and Financial Statement [removed: Schedules](#i8f04c147560c48a7bb5358179696a625_274)] [added: Schedules](#i2dd641cc643b4c5aaf649d4cde640538_277)] | | | [removed: [93](#i8f04c147560c48a7bb5358179696a625_274)] [added: [97](#i2dd641cc643b4c5aaf649d4cde640538_277)] | | |

| [Item [removed: 16.](#i8f04c147560c48a7bb5358179696a625_277)] [added: 16.](#i2dd641cc643b4c5aaf649d4cde640538_280)] | | | [Form 10-K [removed: Summary](#i8f04c147560c48a7bb5358179696a625_277)] [added: Summary](#i2dd641cc643b4c5aaf649d4cde640538_280)] | | | [removed: [93](#i8f04c147560c48a7bb5358179696a625_277)] [added: [97](#i2dd641cc643b4c5aaf649d4cde640538_280)] | | |

| [Consolidated Financial [removed: Statements](#i8f04c147560c48a7bb5358179696a625_286)] [added: Statements](#i2dd641cc643b4c5aaf649d4cde640538_289)] | | | | | | F- [removed: [1](#i8f04c147560c48a7bb5358179696a625_286)] [added: [1](#i2dd641cc643b4c5aaf649d4cde640538_289)] | | |

These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” "assume," “believe,” “contemplate,” “continue," "could," “estimate,” “expect,” “forecast,” “goal,” “guidance,” “hope,” “intend,” “may,” “objective,” [added: "outlook,"] “plan,” “possible,” "potential," [removed: “predict”] [added: “predict,”] “project,” “should,” “target,” “will,” “would” or the negative of these words or other words and terms of similar meaning.

- our expectations about [removed: continued] growth through acquisitions and key collaborative [removed: relationships;][added: relationships and funding arrangements;]

- our ability to obtain and maintain adequate coverage, pricing and reimbursement from third-party [removed: payors;][added: payors and governments;]

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

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

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

- patent terms, patent term extensions, patent office actions and expected availability and periods of regulatory [removed: exclusivity,] [added: exclusivities,] as well as our ability to adequately enforce existing [removed: patents, including our European patent related to TECFIDERA;][added: patents;]

- our ability to effectively implement our corporate strategy which includes significant investment in product and pipeline candidates, including but not limited to [removed: felzartamab] [added: felzartamab, litifilimab] and [removed: nusinersen;][added: salanersen;]

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

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

| [PART I](#i2dd641cc643b4c5aaf649d4cde640538_25) | | | | | | | | |

| [PART II](#i2dd641cc643b4c5aaf649d4cde640538_97) | | | | | | | | |

| [PART III](#i2dd641cc643b4c5aaf649d4cde640538_256) | | | | | | | | |

| [PART IV](#i2dd641cc643b4c5aaf649d4cde640538_274) | | | | | | | | |

| [Signatures](#i2dd641cc643b4c5aaf649d4cde640538_286) | | | | | | [100](#i2dd641cc643b4c5aaf649d4cde640538_286) | | |

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

government expenditures, including the impact of pricing actions and reduced reimbursement for our products, as well as the potential impact of legislative and regulatory changes and priorities, including actions related to MFN drug pricing;

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

| Alcyone | | | Alcyone Therapeutics, Inc. | | |

| CNS | | | Central Nervous System | | |

| Dayra | | | Dayra Therapeutics, Inc. | | |

| HHS | | | U.S. Department of Health and Human Services | | |

| IND | | | Investigational New Drug | | |

| LEQEMBI Collaboration Agreement | | | Amended and Restated Collaboration Agreement entered into by Biogen MA Inc. and Eisai Co., Ltd. on October 22, 2017, as amended on March 13, 2022 | | |

| LTI | | | Long-term Incentive | | |

| MFN | | | Most-Favored-Nation | | |

| MorphoSys | | | MorphoSys AG | | |

| MVI | | | Microvascular Inflammation in Kidney Transplant Patients | | |

| OBBBA | | | One Big Beautiful Bill Act | | |

| Organon | | | Organon LLC | | |

| RNAi | | | RNA Interference | | |

| Supernus | | | Supernus Pharmaceuticals, Inc. | | |

| VA | | | U.S. Department of Veterans Affairs | | |

| Vanqua | | | Vanqua Bio, Inc. | | |

| VAT | | | Value-added Tax | | |

| | | | | | |

| | | | | | |

| [PART I](#i8f04c147560c48a7bb5358179696a625_25) | | | | | | | | |

| [PART II](#i8f04c147560c48a7bb5358179696a625_91) | | | | | | | | |

| [PART III](#i8f04c147560c48a7bb5358179696a625_253) | | | | | | | | |

| [PART IV](#i8f04c147560c48a7bb5358179696a625_271) | | | | | | | | |

| [Signatures](#i8f04c147560c48a7bb5358179696a625_283) | | | | | | [96](#i8f04c147560c48a7bb5358179696a625_283) | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| 125 Broadway | | | 125 Broadway, Cambridge, MA | | |

| 300 Binney Street | | | 300 Binney Street, Cambridge, MA | | |

| ATV | | | Antibody Transport Vehicle | | |

| CCDAA | | | Climate Corporate Data Accountability Act | | |

| CISA | | | Cybersecurity and Infrastructure Security Agency | | |

| CJEU | | | Court of Justice of the European Union | | |

| CRFRA | | | Climate-Related Financial Risk Act | | |

| DEA | | | Drug Enforcement Agency | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| ERISA | | | Employee Retirement Income Security Act of 1974 | | |

| FDIC | | | Federal Deposit Insurance Corporation | | |

| LHI | | | Large Hemispheric Infarction | | |

| MDD | | | Major Depressive Disorder | | |

| NCD | | | National Coverage Decision | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| PMDA | | | Pharmaceuticals and Medical Devices Agency | | |

| SAG | | | Scientific Advisory Group | | |

| TBA | | | Technical Boards of Appeal | | |

| TGN | | | Trigeminal Neuralgia | | |

| VA | | | Veterans Administration | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

We maintain a technology and cybersecurity program, which includes information security, as part of our overall risk management process with the aim that our information systems, including those of our vendors and other [removed: third-parties,] [added: third parties,] will be resilient, effective and capable of safeguarding against emerging risks and cybersecurity threats.

Our program's maturity and operational readiness are regularly evaluated by [added: internal audit and] independent experts using the U.S. NIST's CyberSecurity Framework and penetration tests.

Our technology and cybersecurity program is the principal responsibility of our Chief Information Officer and CISO, each of whom have over 20 years of [removed: experience in information systems, including cybersecurity training and experience.]

Risk Factors - A breakdown or breach of our information systems could subject us to liability or interrupt the operation of our [removed: business*,] [added: business operations*,] included in this report.

We have designed our cybersecurity policies and procedures to align with international regulatory frameworks, including the NIS2 Directive in the E.U. Our program integrates periodic reviews and updates to ensure our controls remain effective and compliant with evolving international regulations.

experience in information systems, including cybersecurity training and experience.

- Compliance with regulatory requirements and industry standards, including international regulations such as the NIS2 Directive in the E.U.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

- Compliance with regulatory requirements and industry standards.

Below is a summary of our significant properties owned and leased as of December 31, [removed: 2024.][added: 2025.]

| RTP, North Carolina | | | | | | [removed: 1,040,000] [added: 1,237,000] | | | | | | Office, laboratory, manufacturing, warehouse | | | | | | Owned | | |

| Durham, North Carolina | | | | | | [removed: 65,000] [added: 40,000] | | | | | | Warehouse | | | | | | Leased - Expires [removed: 2025] [added: 2030] | | |

Our international lease agreements expire at various dates through the year [removed: 2034.][added: 2047.]

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

The new manufacturing facility [removed: will be] [added: is] approximately 197,000 square feet.

[removed: We estimate the] [added: The] construction of this manufacturing facility [removed: will be] [added: was] completed during [added: 2025 and the majority of the facility was placed in service during the fourth quarter of] 2025.

We believe that our [removed: our] existing properties, including both owned and leased sites, are adequate and suitable for the conduct of our business.

| Athlone, Ireland | | | | | | 47,500 | | | | | | Fill finish manufacturing facility | | | | | | Leased - Expires 2047 | | |

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.

| Weston, Massachusetts | | | | | | 357,000 | | | | | | Office | | | | | | Leased - Expires 2025 | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

Our common stock trades on The Nasdaq Global Select Market under the symbol “BIIB.” As of February [removed: 11, 2025,] [added: 4, 2026,] there were approximately [removed: 392] [added: 372] shareholders of record of our common stock.

[removed: ISSUER] [added: ISSUER] PURCHASES OF EQUITY [removed: SECURITIES][added: SECURITIES]

The following table summarizes our common stock repurchase activity during the fourth quarter of [removed: 2024:][added: 2025:]

| October 1, [removed: 2024] [added: 2025] - October 31, [removed: 2024] [added: 2025] | | | | | | — | | | | | | $ | — | | | | | — | | | | | | $ | 2,050.0 | |

| November 1, [removed: 2024] [added: 2025] - November 30, [removed: 2024] [added: 2025] | | | | | | — | | | | | | $ | — | | | | | — | | | | | | $ | 2,050.0 | |

| December 1, [removed: 2024] [added: 2025] - December 31, [removed: 2024] [added: 2025] | | | | | | — | | | | | | $ | — | | | | | — | | | | | | $ | 2,050.0 | |

(1) There were no share repurchases during the fourth quarter of [removed: 2024.][added: 2025.]

There were no [removed: share] repurchases of our common stock during the years ended December 31, [added: 2025,] 2024 and 2023.

Approximately $2.1 billion remained available under our 2020 Share Repurchase Program as of December 31, [removed: 2024.][added: 2025.]

The performance graph below assumes the investment of $100.00 on December 31, [removed: 2019,] [added: 2020,] in our common stock and each of the three indexes, with dividends being reinvested.

[removed: ][added: ]

| | | | | | | [removed: 2019] [added: 2020] | | | | | | [removed: 2020] [added: 2021] | | | | | | [removed: 2021] [added: 2022] | | | | | | [removed: 2022] [added: 2023] | | | | | | [removed: 2023] [added: 2024] | | | | | | [removed: 2024] [added: 2025] | | |

| Biogen Inc. | | | | | | $100.00 | | | | | | $97.98 | | | | | | $113.08 | | | | | | $105.65 | | | | | | $62.43 | | | | | | $71.84 | | |

| Nasdaq Pharmaceutical Index | | | | | | $100.00 | | | | | | $124.39 | | | | | | $138.51 | | | | | | $143.88 | | | | | | $156.19 | | | | | | $200.89 | | |

| S&P 500 Index | | | | | | $100.00 | | | | | | $128.71 | | | | | | $105.40 | | | | | | $133.10 | | | | | | $166.40 | | | | | | $196.16 | | |

| Nasdaq Biotechnology Index | | | | | | $100.00 | | | | | | $100.02 | | | | | | $89.90 | | | | | | $94.03 | | | | | | $93.49 | | | | | | $124.75 | | |

Under our 2020 Share Repurchase Program, we repurchased and retired approximately 3.6 million shares of our common stock at a cost of approximately $750.0 million during the year ended December 31, 2022.

In August 2022 the IRA was signed into law.

Among other things, the IRA levies a 1.0% excise tax on net stock repurchases after December 31, 2022.

While we have historically made discretionary share repurchases, we had no share repurchases of our common stock during the years ended December 31, 2024 and 2023.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| Biogen Inc. | | | | | | $100.00 | | | | | | $82.52 | | | | | | $80.85 | | | | | | $93.31 | | | | | | $87.19 | | | | | | $51.52 | | |

| Nasdaq Pharmaceutical Index | | | | | | $100.00 | | | | | | $110.52 | | | | | | $137.47 | | | | | | $153.08 | | | | | | $159.01 | | | | | | $172.62 | | |

| S&P 500 Index | | | | | | $100.00 | | | | | | $118.40 | | | | | | $152.39 | | | | | | $124.79 | | | | | | $157.59 | | | | | | $197.02 | | |

| Nasdaq Biotechnology Index | | | | | | $100.00 | | | | | | $126.42 | | | | | | $126.45 | | | | | | $113.65 | | | | | | $118.87 | | | | | | $118.20 | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

The information required by this Item 8 is contained on pages F-1 through [removed: F-83] [added: F-79] of this report and is incorporated herein by reference.

We have carried out an evaluation, under the supervision and with the participation of our management, including our principal executive officer and principal financial officer, of the effectiveness of the design and operation of our disclosure controls and procedures (as defined in Rules 13a-15(e) or 15d-15(e) under the Securities Exchange Act of 1934, as amended), as of December 31, [removed: 2024.][added: 2025.]

There were no changes in our internal control over financial reporting during the quarter ended December 31, [removed: 2024,] [added: 2025,] that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

Our management assessed the effectiveness of our internal control over financial reporting as of December 31, [removed: 2024.][added: 2025.]

Based on our assessment, our management has concluded that, as of December 31, [removed: 2024,] [added: 2025,] our internal control over financial reporting is effective based on those criteria.

The effectiveness of our internal control over financial reporting as of December 31, [removed: 2024,] [added: 2025,] has been audited by PricewaterhouseCoopers LLP, an independent registered public accounting firm, as stated in their attestation report, which is included herein.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[removed: RULE 10b5-1] TRADING ARRANGEMENTS

From time to time, our officers (as defined in Rule 16a-1(f)) and directors may enter [removed: into] [added: into, amend or terminate] Rule 10b5-1 or non-Rule 10b5-1 trading arrangements (as each such term is defined in Item 408 of Regulation S-K).

During the fourth quarter of 2025 there were no trading arrangements for the purchase or sale of our securities entered into, amended or terminated by our officers and directors.

During the fourth quarter of 2024 our officers and directors took the following actions with respect to 10b5-1 trading arrangements:

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| | | | | | | | | | | | | | | | | | | Trading Arrangement | | | | | | | | | | | | | | | | | | | | |

| Name and Position | | | | | | Action | | | | | | Date | | | | | | Rule 10b5-1 | | | | | | Non-Rule 10b5-1 | | | | | | Total Shares to be Sold | | | | | | Expiration Date | | |

| Stephen A. Sherwin, Director | | | | | | Adopt | | | | | | 11/7/2024 | | | | | | X | | | | | | — | | | | | | 8,760 | | | | | | 05/08/2025 | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

The response to the remainder of this item is incorporated by reference from the discussion responsive thereto in the sections entitled “*Proposal 1 - Election of Directors,” “Corporate Governance”* and “*Miscellaneous - Stockholder Proposals*” contained in the proxy statement for our [removed: 2025] [added: 2026] annual meeting of stockholders.

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “*Executive Compensation Tables,*” *"Compensation Discussion and Analysis"* and *“Corporate Governance”* contained in the proxy statement for our [removed: 2025] [added: 2026] annual meeting of stockholders.

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled *“Stock Ownership”* and *“Equity Compensation Plan Information”* contained in the proxy statement for our [removed: 2025] [added: 2026] annual meeting of stockholders.

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “*Certain Relationships and Related Person Transactions*” and *“Corporate Governance*” contained in the proxy statement for our [removed: 2025] [added: 2026] annual meeting of stockholders.

The response to this item is incorporated by reference from the discussion responsive thereto in the section entitled “*Proposal 2 - Ratification of the Selection of our Independent Registered Public Accounting Firm*” contained in the proxy statement for our [removed: 2025] [added: 2026] annual meeting of stockholders.

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| Report of Independent Registered Public Accounting Firm (PCAOB ID 238) | | | | | | [removed: F-81] [added: F-80] | | |

The exhibits listed on the Exhibit Index beginning on page [removed: 95,] [added: 98,] which is incorporated herein by reference, are filed or furnished as part of this report or are incorporated into this report by reference.

| 3.5 | | | | | | [Fifth Amended and Restated [removed: Bylaws](https://www.sec.gov/Archives/edgar/data/875045/000119312523293433/d850833dex31.htm) [of] [added: Bylaws of] Biogen [removed: Inc.](https://www.sec.gov/Archives/edgar/data/875045/000119312523293433/d850833dex31.htm) [Filed] [added: Inc. Filed] as Exhibit 3.1 to our Current Report on Form 8-K filed on December 12, 2023.](https://www.sec.gov/Archives/edgar/data/875045/000119312523293433/d850833dex31.htm) | | |

| [removed: 4.6+] [added: 4.7] | | | | | | [Description of [removed: Securities.](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000087504524000009/biib-20231231.htm) [](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000087504524000009/biib-20231231.htm)[Filed] [added: Securities. Filed] as Exhibit 4.6 to our Annual Report on [removed: Form](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000087504524000009/biib-20231231.htm) [10-K] [added: Form 10-K] for the year ended December 31, [removed: 202](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000087504524000009/biib-20231231.htm)[3.](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000087504524000009/biib-20231231.htm)] [added: 2023.](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000087504524000009/biib-20231231.htm)] | | |

| 10.5 | | | | | | [Form of performance share award agreement under the Biogen Inc. 2024 Omnibus Equity [removed: P](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit103-formofpsuawarda.htm)[lan.] [added: Plan.] Filed as Exhibit 10.3 to our Quarterly Report on Form 10-Q for the quarter ended June 30, [removed: 202](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit103-formofpsuawarda.htm)[4.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit103-formofpsuawarda.htm)] [added: 2024.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit103-formofpsuawarda.htm)] | | |

| 10.7 | | | | | | [removed: [F](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[orm] [added: [Form] of non-employee [removed: dire](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[ctor] [added: director] restricted stock [removed: u](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[ni](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[t awar](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[d] [added: unit award] agreement under the Biogen Inc. 2024 [removed: Omni](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[bus Equity](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm) [Plan.] [added: Omnibus Equity Plan.] Filed as Exhibit 10.5 to our Quarterly Report on Form [removed: 10-](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm)[Q] [added: 10-Q] for the quarter ended June 30, 2024.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000025/exhibit105-formofrsuawarda.htm) | | |

| [removed: 10.14+] [added: 10.14] | | | | | | [Voluntary Board of Directors Savings Plan.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1014-voluntaryboard.htm) [added: [Filed as Exhibit 10.14 to our Annual Report on Form 10-K for the year ended December 31, 202](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1014-voluntaryboard.htm)[4.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1014-voluntaryboard.htm)] | | |

| [removed: 10.15+] [added: 10.15] | | | | | | [Biogen Inc. Supplemental Savings Plan.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1015-supplementalsa.htm) [added: [Filed as](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1015-supplementalsa.htm) [Exhibit 10.15 to our Annual Report on Form 10-K for the year ended December 31, 202](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1015-supplementalsa.htm)[4.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit1015-supplementalsa.htm)] | | |

| 10.22* | | | | | | [Letter amending employment arrangement of Susan Alexander dated February 28, [removed: 2020.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm) [](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm)[Filed] [added: 2020. Filed] as Exhibit [removed: 10.32](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm) [to] [added: 10.32 to] our Annual Report on Form 10-K for the year ended December [removed: 3](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm)[1, 202](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm)[3.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm)] [added: 31, 2023.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1032-salexanderamen.htm)] | | |

| 10.23* | | | | | | [Letter regarding employment arrangement of Rachid Izzar dated August 1, [removed: 2019.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1033-rachidemployme.htm) [](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1033-rachidemployme.htm)[Filed] [added: 2019. Filed] as Exhibit 10.33 to our Annual Report on Form 10-K for the year ended December 31, 2023.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit1033-rachidemployme.htm) | | |

| 10.25* | | | | | | [removed: [L](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm)[etter] [added: [Letter] regarding employment arrangement of [removed: Robi](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm)[n] [added: Robin] Kramer dated October 28, 2024. [removed: Fil](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm)[ed] [added: Filed] as [removed: Exhi](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm)[b](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm)[i](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm)[t] [added: Exhibit] 10.1 to our Current Report on Form 8-K filed on October 30, 2024.](https://www.sec.gov/ix?doc=/Archives/edgar/data/0000875045/000119312524247628/d890797d8k.htm) | | |

| [removed: 10.26] [added: 10.27] | | | | | | [Amended and Restated Collaboration Agreement, dated October 22, 2017, between Biogen MA Inc. and Eisai Co., LTD. Filed as Exhibit 10.45 to our Annual Report on Form 10-K for the year ended December 31, 2022.](https://www.sec.gov/Archives/edgar/data/875045/000087504523000009/exhibit1045amendedandresta.htm) | | |

| [removed: 10.27] [added: 10.28] | | | | | | [First Amendment to Amended and Restated Collaboration Agreement, dated March 13, 2022, between Biogen MA Inc. and Eisai Co., LTD. Filed as Exhibit 10.46 to our Annual Report on Form 10-K for the year ended December 31, 2022.](https://www.sec.gov/Archives/edgar/data/875045/000087504523000009/exhibit1046firstamendmentt.htm) | | |

| 19.1+ | | | | | | [Policy relating to insider [removed: trading.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/exhibit191-insidertradinga.htm)] [added: trading.](https://www.sec.gov/Archives/edgar/data/875045/000087504526000013/exhibit191-insidertradinga.htm)] | | |

| 21+ | | | | | | [removed: [Subsidiaries.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/biib-20241231xex21.htm)] [added: [Subsidiaries.](https://www.sec.gov/Archives/edgar/data/875045/000087504526000013/biib-20251231xex21.htm)] | | |

| 23+ | | | | | | [Consent of PricewaterhouseCoopers LLP, an Independent Registered Public Accounting [removed: Firm.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/biib-20241231xex23.htm)] [added: Firm.](https://www.sec.gov/Archives/edgar/data/875045/000087504526000013/biib-20251231xex23.htm)] | | |

| 31.1+ | | | | | | [Certification of the Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of [removed: 2002.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/biib-20241231xex311.htm)] [added: 2002.](https://www.sec.gov/Archives/edgar/data/875045/000087504526000013/biib-20251231xex311.htm)] | | |

| 31.2+ | | | | | | [Certification of the Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of [removed: 2002.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/biib-20241231xex312.htm)] [added: 2002.](https://www.sec.gov/Archives/edgar/data/875045/000087504526000013/biib-20251231xex312.htm)] | | |

| 32.1++ | | | | | | [Certification of the Chief Executive Officer and the Chief Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of [removed: 2002.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000009/biib-20241231xex321.htm)] [added: 2002.](https://www.sec.gov/Archives/edgar/data/875045/000087504526000013/biib-20251231xex321.htm)] | | |

| 97.1 | | | | | | [Policy relating to recovery of erroneously awarded [removed: compensation.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit971-clawbackpolicy.htm) [](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit971-clawbackpolicy.htm)[Filed] [added: compensation. Filed] as Exhibit 97.1 to our Annual Report on Form 10-K for the year ended December 31, 2023.](https://www.sec.gov/Archives/edgar/data/875045/000087504524000009/exhibit971-clawbackpolicy.htm) | | |

| 101++ | | | | | | The following materials from Biogen Inc.’s Annual Report on Form 10-K for the year ended December 31, [removed: 2024,] [added: 2025,] formatted in iXBRL (Inline Extensible Business Reporting Language): (i) the Consolidated Statements of Income, (ii) the Consolidated Statements of Comprehensive Income, (iii) the Consolidated Balance Sheets, (iv) the Consolidated Statements of Cash Flow, (v) the Consolidated Statements of Equity and (vi) Notes to Consolidated Financial Statements. | | |

Date: February [removed: 12, 2025][added: 6, 2026]

| /S/ CHRISTOPHER A. VIEHBACHER | | | | | | Director and Chief Executive Officer (principal executive officer) | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ [removed: MICHAEL R. MCDONNELL] [added: ROBIN C. KRAMER] | | | | | | Executive Vice President and Chief Financial Officer (principal financial officer) | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ CAROLINE D. DORSA | | | | | | Director and Chair of the Board of Directors | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ MARIA C. FREIRE | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ WILLIAM A. HAWKINS | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ SUSAN LANGER | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ JESUS B. MANTAS | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ LLOYD B. MINOR | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ SIR MENELAS PANGALOS | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ MONISH PATOLAWALA | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ ERIC K. ROWINSKY | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| /S/ STEPHEN A. SHERWIN | | | | | | Director | | | | | | February [removed: 12, 2025] [added: 6, 2026] | | |

| Report of Independent Registered Public Accounting Firm (PCAOB ID 238) | | | | | | [removed: F-81] [added: F-80] | | |

| | | | | | | [removed: 2024] [added: 2025] | | | | | | [removed: 2023] [added: 2024] | | | | | | [removed: 2022] [added: 2023] | | |

| Product revenue, net | | | | | | $ | [removed: 7,213.5] [added: 7,119.4] | | | | | $ | [removed: 7,246.7] [added: 7,213.5] | | | | | $ | [removed: 7,987.8] [added: 7,246.7] | |

| Revenue from anti-CD20 therapeutic programs | | | | | | [removed: 1,749.9] [added: 1,860.6] | | | | | | [removed: 1,689.6] [added: 1,749.9] | | | | | | [removed: 1,700.5] [added: 1,689.6] | | |

| Alzheimer's collaboration revenue | | | | | | [removed: 59.9] [added: 177.7] | | | | | | [removed: —] [added: 59.9] | | | | | | — | | |

| Contract manufacturing, royalty and other revenue | | | | | | [removed: 652.6] [added: 732.9] | | | | | | [removed: 899.3] [added: 652.6] | | | | | | [removed: 485.1] [added: 899.3] | | |

| Total revenue | | | | | | [removed: 9,675.9] [added: 9,890.6] | | | | | | [removed: 9,835.6] [added: 9,675.9] | | | | | | [removed: 10,173.4] [added: 9,835.6] | | |

| Cost of sales, excluding amortization and impairment of acquired intangible assets | | | | | | [removed: 2,310.4] [added: 2,404.2] | | | | | | [removed: 2,533.4] [added: 2,310.4] | | | | | | [removed: 2,278.3] [added: 2,533.4] | | |

| 4.6 | | | | | | [Fourth Supplemental Indenture, dated as of May 12, 2025, between the Company and U.S. Bank Trust Company, National Association (as successor to U.S. Bank, National Association), including the forms of Global Notes attached as Exhibit A, Exhibit B and Exhibit C, respectively, thereto. Filed as Exhibit 4.2 to our Current Report on Form 8-K filed on May 12, 2025.](https://www.sec.gov/Archives/edgar/data/875045/000119312525117854/d13940dex42.htm) | | |

| 10.26 | | | | | | [Letter regarding employment arrangement of Priya Singhal dated January 3, 2023. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q filed on July 31, 2025.](https://www.sec.gov/Archives/edgar/data/875045/000087504525000033/exhibit101-priyasinghalemp.htm) | | |

| /S/ SEAN GODBOUT | | | | | | Vice President, Chief Accounting Officer and Global Corporate Controller (principal accounting officer) | | | | | | February 6, 2026 | | |

| Sean Godbout | | | | | | | | | | | | | | |

| Research and development | | | | | | 1,778.6 | | | | | | 1,980.3 | | | | | | 2,445.4 | | |

| Impairment of ROU asset | | | | | | 52.9 | | | | | | — | | | | | | — | | |

| | | | 2025 | | | | | | 2024 | | |

| Current portion of marketable securities | | | 807.2 | | | | | | — | | |

| Marketable securities | | | 431.9 | | | | | | — | | |

| Goodwill | | | 6,491.1 | | | | | | 6,478.9 | | |

| Notes payable | | | 6,286.8 | | | | | | 4,547.2 | | |

| Impairment of ROU asset | | | 52.9 | | | | | | — | | | | | | — | | |

| Acquired in-process research and development | | | 85.0 | | | | | | — | | | | | | — | | |

| Acquired in-process research and development | | | (50.0) | | | | | | — | | | | | | — | | |

| Contingent consideration payments | | | (280.0) | | | | | | — | | | | | | — | | |

| Net income | | | — | | | | | | — | | | | | | — | | | | | | — | | | | | | — | | | | | | — | | | | | | 1,292.9 | | | | | | — | | | | | | — | | | | | | | | | | | | | | | | | | 1,292.9 | | |

| Other | | | — | | | | | | — | | | | | | — | | | | | | — | | | | | | 0.6 | | | | | | — | | | | | | — | | | | | | — | | | | | | — | | | | | | | | | | | | | | | | | | 0.6 | | |

| Balance, December 31, 2025 | | | — | | | | | | $ | — | | | | | 170.5 | | | | | | $ | 0.1 | | | | | $ | 863.1 | | | | | $ | (182.0) | | | | | $ | 20,552.7 | | | | | (23.8) | | | | | | $ | (2,977.1) | | | | | | | | | | | | | | | | | $ | 18,256.8 | |

| Balance, December 31, 2024 | | | — | | | | | | $ | — | | | | | 169.5 | | | | | | $ | 0.1 | | | | | $ | 569.4 | | | | | $ | (136.2) | | | | | $ | 19,259.8 | | | | | (23.8) | | | | | | $ | (2,977.1) | | | | | $ | 16,716.0 | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

We base our estimates on historical experience and on various other assumptions that we believe are

Our liability for Medicaid rebates consists of estimates for claims

- *IRA Medicare rebates:* relate to our estimated obligation under the IRA for the manufacturer’s portion of the Medicare Part D redesign.

Rebate accruals are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expense and other within our consolidated balance sheets.

The calculation of the accrual for these rebates is based on an estimate of our Medicare population and the estimated manufacturer portion of our obligation under the Part D Redesign.

As of December 31, 2025, cash equivalents were comprised of money market funds, overnight reverse repurchase agreements, short-term debt securities and commercial paper with maturities less than three months from the date of purchase.

monitoring that we perform throughout the manufacturing process.

the same line as the underlying hedged item.

*Acquired In-process Research and Development, Upfront and Milestone Expense*

Acquired in-process research and development, upfront and milestone expense consists of upfront fees and milestones paid to third-party collaborators as well as charges associated with the acquisition of an asset or group of assets with no alternative future use that did not meet the definition of a business under applicable accounting standards.

| ASU No. 2025-06, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software | | | | | | This standard modernizes the accounting for software costs, including updating guidance on the recognition and measurement of costs incurred in connection with development and implementation activities related to internal-use software. | | | | | | Annual reporting for fiscal periods beginning after December 15, 2027, and interim periods within those annual reporting periods. Early adoption is permitted. | | | | | | We are currently evaluating the potential impact that this new standard will have on our consolidated financial statements and related disclosures. | | |

| ASU No. 2025-07, Derivatives and Hedging (Topic 815) and Revenue from Contracts with Customers (Topic 606): Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration from a Customer in a Revenue Contract | | | | | | This standard refines and expands the existing scope exceptions that exclude certain contracts, including certain R&D funding arrangements, from derivative accounting, and clarifies the accounting for share-based noncash consideration received from a customer. | | | | | | Annual reporting for fiscal years beginning after December 15, 2026, and interim periods within those annual reporting periods. Early adoption is permitted. | | | | | | We have early adopted this new standard on a modified retrospective basis as of January 1, 2025. Adoption did not have a material impact on our condensed consolidated financial statements and related disclosures. | | |

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.

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

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | |

| --- | --- | --- | --- | --- | --- |

| | | | | | |

| --- | --- | --- | --- | --- | --- |

| | | | | | |

| --- | --- | --- | --- | --- | --- |

| | | | | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | |

| Michael R. McDonnell | | | | | | | | | | | | | | |

| /S/ ROBIN C. KRAMER | | | | | | Senior Vice President, Chief Accounting Officer (principal accounting officer) | | | | | | February 12, 2025 | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

BIOGEN INC. AND SUBSIDIARIES

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | | | | | | | | | | | | | | | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| Research and development | | | | | | 2,041.8 | | | | | | 2,462.0 | | | | | | 2,231.1 | | |

| | | | | | | | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | | | | |

| Gain on sale of building, net | | | | | | — | | | | | | — | | | | | | (503.7) | | |

| | | | | | | | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | | | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | | | | | | | | | | | | | | | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| Gains (losses) on net investment hedges, net of tax | | | | | | — | | | | | | — | | | | | | (25.5) | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | | | | | | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| | | | | | | | | | | | |

| | | | | | | | | | | | |

| Notes payable and term loan | | | 4,547.2 | | | | | | 6,788.2 | | |

[Table o](#i8f04c147560c48a7bb5358179696a625_10)[f](#i8f04c147560c48a7bb5358179696a625_10) [Contents](#i8f04c147560c48a7bb5358179696a625_10)

| | | | | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | |