Biogen — May 1, 2025 release

and Brazil Advanced key development programs, supporting a late-stage pipeline with multi-billion dollar potential • Zorevunersen agreement with Stoke broadens Biogen’s rare disease pipeline and leverages global expertise commercializing high-value, disease-modifying medicines for rare genetic diseases - The pivotal Phase 3 study is expected to initiate in the coming months • Felzartamab Phase 3 study initiated in late antibody-mediated rejection in kidney transplant patients with plans to initiate Phase 3 trials of felzartamab in IgA nephropathy and primary membranous nephropathy in 2025 • BIIB080, a potential first-in-class investigational ASO therapy targeting tau for Alzheimer's disease, received FDA Fast Track designation With the expected underlying business outlook unchanged, Biogen is updating full year 2025 guidance to reflect the $165 million upfront transaction payment to Stoke and more favorable foreign exchange • Expected full year Non-GAAP diluted EPS of $14.50 to $15.50 reflects the ~($0.95) impact from the upfront payment as well as a $0.20 improvement mainly from foreign exchange • Expect full year 2025 total revenue to decline by a mid-single digit percentage at constant currency versus full year 2024 Biogen Inc. (NASDAQ: BIIB) today reported first quarter 2025 financial results. "Biogen delivered strong first-quarter results, supporting our strategy for long-term growth. We are encouraged by the transformation in our commercial product portfolio, with approximately 45% of total product revenue in the first quarter derived from important medicines outside of our MS business," said Christopher A. Viehbacher, President and Chief Executive Officer. “In an environment of potential tariffs and medical supply security concerns, Biogen operates a significant manufacturing presence in the U.S. Roughly 75% of our 2024 U.S. product revenues were generated by products which have manufacturing operations in the U.S. In addition, Biogen pays substantial taxes in the U.S. since our U.S. market revenues are almost entirely taxable in the U.S. at Federal and state tax rates.” 1 Financial Highlights Q1 '25 Q1 '24 △ r (CC * ) Total Revenue (in millions) $2,431