Biogen Secures European Approval for High-Dose SPINRAZA, Bolstering Rare-Disease Portfolio

What happened

Biogen received European Commission approval for a high-dose regimen of SPINRAZA for spinal muscular atrophy, allowing 50 mg loading doses and 28 mg maintenance doses every four months. This update enables a more rapid loading phase and less frequent injections, potentially improving patient convenience and adherence in a competitive market. SPINRAZA is a key revenue driver in Biogen's rare-disease segment, contributing $374 million in Q3 2025 as the company transitions away from declining multiple sclerosis sales. The approval reinforces Biogen's strategy to grow its rare neurology assets, including Skyclarys and Qalsody, to offset structural MS erosion. However, this is an incremental development that does not address broader risks like Alzheimer's drug Leqembi adoption or business development-driven EPS volatility.

Implication

The high-dose regimen could help SPINRAZA retain market share against gene therapies like Novartis's ZOLGENSMA by offering improved dosing convenience. However, the SMA market faces intense competition and pricing pressures, limiting potential revenue upside from this update. For investors, this news aligns with Biogen's rare-disease growth pillar but fails to mitigate key thesis risks such as Leqembi scalability or further EPS guidance cuts from business development charges. Monitoring SPINRAZA sales post-approval is crucial to confirm it sustains double-digit growth, as required to offset MS decline. Ultimately, while operationally positive, this does not justify a shift from the 'WAIT' rating without clearer evidence of 2026 revenue acceleration above 3%.

Thesis delta

The European approval for high-dose SPINRAZA slightly strengthens Biogen's rare-disease segment, supporting the existing thesis that rare neurology growth must counter MS erosion. However, it does not change the core investment call, as the critical drivers remain Leqembi adoption and rare-disease revenue exceeding 10% annual growth in 2026. Investors should still await 2026 guidance and more quarters of launch product data before considering a more bullish stance.