FDA Priority Review for Biogen's At-Home Leqembi Injection Advances Alzheimer's Strategy Amid Transition Risks

What happened

The FDA has accepted Biogen and Eisai's supplemental BLA for LEQEMBI IQLIK as a subcutaneous starting dose for early Alzheimer's disease under priority review, targeting a May 24, 2026 action date. This aligns with Biogen's strategic push to expand Leqembi's accessibility, a key growth pillar in its transition from declining multiple sclerosis revenue to higher-risk neurology and rare-disease assets. Leqembi is already the leading prescribed anti-amyloid therapy, and subcutaneous dosing could improve patient convenience and retention, potentially boosting Alzheimer's collaboration revenue. However, the DeepValue report highlights that Leqembi's current scale remains insufficient to offset structural MS erosion, with repeated EPS guidance cuts from business-development charges pressuring near-term earnings. While this regulatory step is positive, it does not immediately resolve Biogen's flat revenue trajectory or the need for sustained rare-disease growth to justify its valuation.

Implication

This development supports Biogen's bull scenario where successful subcutaneous adoption drives Alzheimer's revenue, but investors must recognize that approval is not guaranteed and real-world uptake faces MRI monitoring and safety hurdles. The priority review accelerates the potential launch timeline, yet adoption will depend on overcoming infrastructure bottlenecks that have constrained Leqembi's scale relative to Biogen's MS base. Biogen's valuation at ~16.8x trailing EPS already prices in some success, so further upside requires outperformance in rare-disease segments to offset ongoing MS decline. Critical investors should monitor upcoming 2026 guidance for ≥3% revenue growth and launch products sustaining ≥25% year-over-year gains as key catalysts. Until then, the WAIT rating remains appropriate, with this news reinforcing the need for patience rather than prompting immediate action amid persistent EPS volatility.

Thesis delta

The new article does not fundamentally shift the investment thesis but incrementally increases the probability of the bull scenario by enhancing Leqembi's convenience and market penetration potential. However, the core challenges—including structural MS decline, rare-disease growth sustainability, and EPS volatility from business-development charges—remain unchanged, keeping the overall thesis intact with a slight positive bias that still requires confirmation through 2026 guidance.