Biogen (BIIB) Stock Forecast & Price Target

Biogen is attractive because its base business appears more resilient than the market assumes, with the legacy multiple sclerosis franchise still generating 40% of 2025 revenue and CD20 collaboration agreements contributing another 19%, while erosion looks manageable rather than catastrophic. Biogen is also broadening its growth mix through Spinraza, Leqembi, Skyclarys, Zurzuvae, and Qalsody, and the 3Q26 results showed that the growth portfolio already represents 63% of core pharmaceutical revenue, supporting revenue diversification and better long-term visibility. Biogen is further supported by a catalyst-rich pipeline and operating leverage, with 3Q26 revenues of about $2.8B, non-GAAP EPS of $2.62, and multiple late-stage readouts across lupus, AMR, and Dravet syndrome that could unlock incremental value over 2027.

Biogen is facing a challenging fundamental setup because its largest revenue generator, the multiple sclerosis franchise, is already in decline and still accounted for 40% of total revenue in 2025, leaving the company highly exposed to erosion in a core business. Its other major revenue stream, the CD20 collaboration with Roche, contributed 19% of total revenue in 2025, but that dependence does not offset the pressure from competition such as LLY’s donanemab or the risk of slower-than-expected adoption of newer franchises like Leqembi, Skyclarys, and Zurzuvae. The outlook remains negative because Biogen’s growth thesis depends on successful execution across multiple newer products and ongoing clinical programs, yet any disappointment in trials for SLE, CLE, AMR, or DS could further weaken already fragile revenue diversification.