Biogen (BIIB) Stock Forecast & Price Target

Biogen is positioned for outperformance because its mature MS and CD20 franchises continue to provide substantial cash flow, with 2025 revenue contributions of 40% and 19% of total revenue, respectively, even as those legacy businesses face competition and gradual erosion. The outlook is strengthened by faster-growing newer assets—Leqembi at $511MM in 2025 (+140% Y/Y) and Skyclarys at $520MM (+36% Y/Y)—plus optionality from late-stage pipeline readouts such as litifilimab, which could open a $2B+ lupus opportunity if Phase III data are supportive. With added pipeline value in the sum-of-the-parts view and a DCF-based framework implying the shares are undervalued, the risk/reward appears favorable as commercialization and clinical catalysts expand diversification beyond MS.

Biogen is viewed negatively because its core multiple sclerosis franchise, still a major revenue engine, is steadily eroding from competition and generic/biosimilar pressure, with Avonex/Plegridy at $945.6MM, Tysabri at $1.7B, and Tecfidera/Vumerity at $1.4B in 2025, all declining year over year. The company also relies heavily on a concentrated set of products and Roche CD20 economics, while Spinraza’s $1.5B in 2025 sales fell 2% Y/Y, underscoring limited growth in key legacy assets. At the same time, the outlook is burdened by difficult-to-forecast pipeline programs and meaningful clinical, reimbursement, and trial-conduct risks in newer franchises such as Leqembi and litifilimab, leaving downside if launch momentum or late-stage readouts disappoint.