Biogen Advances Tau-Targeting Alzheimer's Drug to Phase 3 Despite Mixed Phase 2 Results

Biogen reported mixed Phase 2 results for diranersen (BIIB080) on May 14, 2026 and is advancing the tau-targeting Alzheimer's drug to Phase 3 studies. The trial reduced tau levels in spinal fluid and brains of early-stage patients, correlating with slowed cognitive decline, but failed to achieve its primary efficacy goal of a dose response. The lowest dose showed the best results among three escalating regimens tested.

Phase 2 trial results

• ▪Adam Feuerstein is a senior writer and biotech columnist who reports on the crossroads of drug development, business, Wall Street, and biotechnology.
• ▪Diranersen targets the protein tau, which is toxic to neurons and is believed to play a role in cognitive decline in Alzheimer's patients.
• ▪Biogen investigated three escalating dosing regimens in the Phase 2 study of diranersen.
• ▪Biogen reported mixed results on May 14, 2026 from a Phase 2 clinical trial investigating diranersen (BIIB080) for Alzheimer's disease.

Tau protein reduction

• ▪Diranersen reduced levels of tau in the spinal fluid and brains of patients with early-stage Alzheimer's in the Phase 2 study.
• ▪Tau reductions from diranersen correlated to a slowing of cognitive decline in the Phase 2 study.

Dose response failure

• ▪The lowest dose of diranersen showed the best results in the Phase 2 study.
• ▪The Phase 2 study of diranersen failed to achieve its primary efficacy goal, which was a dose response.

1 source