Biogen's anti-tau Alzheimer drug BIIB080 fails primary endpoint in Phase 2, but shows slower decline

Biogen reported results of its Phase 2 trial of BIIB080, a tau-targeting therapy for Alzheimer’s disease.

The study’s primary endpoint was not met, meaning the drug did not achieve the pre-specified statistical goal.

Nevertheless, the company said patients at all dose levels showed a modest slowing of clinical decline over the 18‑month period.

The data were presented on May 14, 2026, and Biogen highlighted these efficacy signals despite the missed endpoint.

Analysts will monitor how the company adjusts its development plan or designs future studies.