Biogen exits AAV gene therapy, cuts staff and shifts strategy

Biogen has officially ended all gene therapy programs using adeno-associated virus (AAV) capsids, reassigning most team members and laying off about 20 employees.

Why it matters: The move reflects a broader industry retreat from AAV technology due to high costs, safety concerns, and limits on re-dosing. This comes despite past successes in the form of approved AAV-based drugs like Luxturna (from Spark Therapeutics) and Zolgensma (Novartis). It also signals Biogen’s strategic pivot toward more promising, scalable treatment modalities.

Backstory: Biogen began deprioritizing early-stage AAV gene therapy projects in 2023 amid a larger R&D restructuring. In January 2025, it laid off staff to focus on its preclinical pipeline and external partnerships, aiming to revitalize its drug discovery efforts.

Zoom in: Biogen says the strategy shift supports "long-term sustainable growth" and focuses on modalities with higher chances of patient benefit.

Big picture: Biogen joins Roche, Takeda, and Vertex in stepping away from AAV research. Pfizer has exited gene therapy altogether. This trend suggests a shift in biotech toward more economically viable and clinically flexible platforms. Considering that AAV therapies like Zolgensma cost up to $2.3M per dose and can’t be re-dosed, concerns about the economic viability of AAV therapies are understandable.