CEO LETTER Dear Shareholder, Three years ago, we embarked on a journey oftransformation with the goal of delivering long-termvalue for our shareholders with a disciplined andhigh-conviction late-stage pipeline that could driveboth meaningful innovation and sustained growth. Wemade notable progress on this strategy in 2025, whereexecution on commercialization of our growth productsand a sharpened development pipeline focused onneurology, immunology, and rare disease are laying astrong foundation for Biogen’s future. Last year, we generated $9.9 billion in total revenue,with our growth products1up 19% year over year.We also achieved $1 billion in gross operating expensesavings through the Fit for Growth initiative we beganin 2023. This initiative reduced our operational costs,including a 27% reduction in research and development(R&D) spending, and allowed us to redeploy resourcesin areas with the highest potential for returns. We’ve also rebuilt our late-stage pipeline. Today, weare advancing 10 programs in Phase 3 trials, whichhold the potential for five new product launches overthe next several years. Five of these programs werenewly initiated or announced in 2025. In addition, threeof these potential product candidates have received aU.S. Food and Drug Administration (FDA) BreakthroughTherapy Designation in key indications, reflecting theirpotential to bring substantial value to patients in need.The volume, breadth and potential value of our late-stage Phase 3 programs are significant achievementsfor a company of our size as we now head into a multi-year period of potentially registration-enabling studyreadouts beginning in 2026. “Today,a we are advancing 10 programsin Phase 3 triarr ls, which hold the potentialfor five new product launches overvvthe nexteeseveral years.rr” Christopher A. Viehbacher, President and Chief Executive Officer company defined primarily by its focus on neuroscienceto a company advancing science in three areas ofstrength – neurology, immunology, and rare diseases.These are areas where we believe Biogen has a distinctability to lead. Delivering the New Biogen Our focus across these areas, combined with our globalcommercialization and operational capabilities anddisciplined expense management, is foundational todefining Biogen going forward. Building on our expertise in immunology andcommercializing medicines in rare disease, ourpurposeful transformation has shifted us from a As the first FDA-approved oral treatment forpostpartum depression,ZURZUVAEVV®has exceededexpectations, with sales more than doubling in 2025alone. The availability of treatment is helping shifthow society recognizes and addresses this condition,which affects hundreds of thousands of mothersannually, even prompting a majoa r celebrity to voiceunsolicited public support of the medication followingher personal experience with the treatment. With greaterawareness initiatives planned and following Europeanapproval in 2025, we’re positioned for ZURZUVAE’VVscontinued growth. Thisalso enables us to contribute to the growth ofBiogen through business development and mergersand acquisitions as we look to remain agile andstrategically opportunistic. Execution on Growth Products Our portfolio of growth products provides a solidfoundation for the next phase of Biogen’s growth. Fiveof these growth products represent not only first-in-classmedicines, but also first-ever treatments in their diseaseindications – a clear illustration of the strengths ofBiogen as a pioneer.rr Introducing them to the marketrequired us to shape new treatment paradigms, educateproviders and build markets from the ground up –challenges we have met with focus and resilience. Biogen is continuing to see strong performance fromrecent commercial launches.SKYCLARYS®YY,ourmedicine for Friedreich ataxia (FA)FF, experienced 36%revenue growth in 2025, driven by strong patient uptakein regions across the globe. Geographic expansioncontinues, with commercial launches planned for 2026in Latin America, Türkiye and the Middle East. In 2025,we began the Phase 3 BRAVE study in children with FA,a step toward expanding SKYCLARYS in the pediatricsetting and enabling earlier intervention. Sales ofLEQEMBI®grew by 54% year over year2in thefourth quarter of 2025, alongside overall growth of theentire market. With its FDA approval for subcutaneousmaintenance dosing, LEQEMBI® IQLIK™ is also thefirst and only at-home injection offering in this class,and regulatory filings are underway in both Japan andChina. We believe this added option of convenience formaintenance treatment is particularly important as thedata continue to show the long-term, progressive natureof the disease and the value of continuous treatment.Additionally, through our partnership with Eisai Co., Ltd.(Eisai), a supplemental filing for IQLIK initiation –meaning from the start of therapy – has been grantedFDA Priority Review. We expect a decision at theend of May 2026. IQLIK initiation and mai