Biogen has discontinued adeno-associated virus (AAV) gene therapy research, affecting approximately 20 employees focused on capsid development with most reassigned internally, according to Endpoints News reporting. The decision follows similar exits by Pfizer, Roche, Takeda and Vertex Pharmaceuticals, reflecting industry-wide challenges including high manufacturing costs limiting commercial viability, slow progress in tissue-specific targeting, and persistent safety concerns including fatal outcomes in clinical trials. Biogen maintains commitment to rare diseases through alternative modalities with greater near-term patient impact potential.

The company had continued early-stage capsid engineering after 2023 prioritisation shift under CEO Chris Viehbacher, including blood-brain barrier- (BBB) penetrating vectors presented this year. Chief R&D Officer Jane Grogan previously indicated belief in gene therapy's future role but acknowledged unresolved scientific hurdles requiring partnership approaches. Biogen's collaboration with Capsigen concluded in 2023 as part of initial de-prioritisation, with the startup's current status unclear following absence of new funding or partnership announcements.

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