Biogen — Apr 29, 2026 release

Proposed acquisition of Apellis Pharmaceuticals bolsters growth outlook, adding commercialized medicines in immune-mediated retinal disease and nephrology, and deepening the foundation for Biogen's growing nephrology franchise. Transaction is subject to customary closing conditions • Apellis transaction expected to be accretive in 2027 • Apellis is expected to materially increase Biogen’s Non-GAAP diluted EPS compounded annual growth rate through the end of the decade Nephrology franchise further enhanced by agreement with TJ Biopharma to acquire exclusive rights to felzartamab in the Greater China region, potentially one of the largest patient populations globally for IgAN Biogen updates full year 2026 guidance to reflect continued strong business outlook and investment for growth • Full year 2026 Non-GAAP diluted EPS is now expected to be between $14.25 and $15.25, excluding any impact from the Apellis transaction. Updated guidance includes an approximately $1.00 impact from acquired IPR&D charges resulting from ongoing business development activities to support 1 Growth products include SKYCLARYS, QALSODY, ZURZUVAE, VUMERITY and SPINRAZA, plus Biogen's 50% share of net revenue and cost of sales, including royalties, from the LEQEMBI Collaboration. 1 Biogen's growth strategy. This comprises approximately $0.20 recorded in the first quarter and approximately $0.80 expected in the second quarter • Full year 2026 total revenue expected to decline by a mid-single digit percentage versus full year 2025 • With the A