Biogen paid $5.6bn for Apellis Pharmaceuticals — $41 per share, a near 140% premium to Apellis’s 30 March closing price. The market’s response: Biogen shares fell more than 4% the morning the deal was announced.
The acquisition brings Syfovre and Empaveli into Biogen’s commercial lineup. Both are already generating revenue: Syfovre treats geographic atrophy, Empaveli covers a kidney disease. Combined, they pulled in $689m in 2025, and Biogen’s projecting mid-to-high teens growth through at least 2028 as the drugs continue to gain market traction. GlobalData forecasts the pair reaching $1.75bn in combined annual sales by 2031.
Biogen’s MS franchise is fading, and the broader industry is staring down a brutal patent cliff. Only 4% of global drug sales will carry patent protection in 2030, down from 12% in 2022. Generic and biosimilar competition could wipe out $230bn in US sales by then, and Apellis gives Biogen a rare disease growth engine to replace what it’s losing.
Apellis’s kidney disease field infrastructure lets Biogen support commercialization of felzartamab, a late-stage anti-CD38 therapy in IgA nephropathy and two other indications.
William Blair estimates the acquisition adds $1.54bn to Biogen’s top line by 2030. Wall Street’s not buying it yet — but Wall Street also didn’t see the MS cliff coming.
Deal expected to close Q2 2026.