Biogen Advances Alzheimer's Drug Diranersen to Phase III Despite Miss

Biogen (BIIB) announced it will advance its experimental Alzheimer's drug diranersen to late-stage trials after a Phase II study missed its primary endpoint but showed cognitive and biomarker gains.

The Drug

Diranersen is an experimental therapy targeting tau protein, which is believed to play a key role in Alzheimer's disease progression. The drug aims to slow or halt the disease by inhibiting tau accumulation in the brain.

Phase II Results

The Phase II study did not achieve its primary goal of statistically significant cognitive improvement. However, data showed positive trends in secondary measures, including improvements in tau-related biomarkers and slower cognitive decline in a patient subgroup.

Next Steps

Biogen decided to proceed with Phase III trials based on the positive signals from Phase II. The Phase III trial is expected to begin in the second half of 2026 and will include a larger patient population to more precisely test the drug's efficacy.

Competition

The Alzheimer's treatment market is highly competitive, with drugs like Leqembi (Eisai/Biogen) and donanemab (Eli Lilly). Diranersen represents a different approach targeting tau protein rather than amyloid beta, which could give it a competitive edge if proven effective.

Potential Impact on Biogen

If diranersen succeeds in Phase III, it could significantly strengthen Biogen's Alzheimer's portfolio and open a new market for tau-targeting therapies. However, risks remain high given the difficulty of developing effective Alzheimer's drugs.