Story perspectives

Biogen Advances Alzheimer Drug, Gains Fast Track After Missed Endpoint

5/14/2026

Summary

Biogen Advances

Biogen will advance diranersen (BIIB080) to development after Phase 2 data showed tau biomarkers and slower cognitive decline.
The placebo-controlled CELIA trial, which enrolled 416 Alzheimer’s patients and missed its primary CDR-SB endpoint at Week 76, saw all doses cut CSF tau and PET signal.
Serious adverse events increased at the 115 mg dose, prompting the FDA to give Fast Track in 2025 and Biogen to present data at the July AAIC.

Summary

Biogen Shares Slip

Biogen’s shares fell about 5% on the day the diranersen Phase 2 results were disclosed.
Bernstein analyst Christian Moore called the update “net-negative” because it lacked quantitative efficacy data.
Wall Street analysts said the missing detailed results leave investors with unanswered questions about the drug’s commercial potential.
Some investors argued that advancing diranersen into registrational trials could preserve long-term value for Biogen’s Alzheimer’s pipeline.

Summary

Biogen Hits Phase-3

Biogen moved diranersen to Phase 3 after trial data showed tau reduction and cognitive benefit, which Dr. Priya Singhal called unprecedented.
Diranersen is an antisense oligonucleotide that lowers tau production, marking Biogen’s shift from amyloid-targeting drugs to a tau-focused Alzheimer’s approach.
Biogen now adds a tau candidate to a portfolio that includes amyloid drugs Aduhelm and Leqembi, while Eli Lilly also pursues tau-lowering therapies, intensifying market competition.

History

Historical Context

In the 1980s, neuroscientist William K. Summers patented tacrine (U.S. Patent 4,816,456, 1989) and showed oral benefit in a 1986 NEJM trial, but faced FDA scrutiny until the agency approved it in 1998 as the first FDA-approved Alzheimer’s drug. SmithKline Beecham marketed it as Cognex, generating $1.2 billion in U.S. sales and reaching about 4.5 million patients.

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Biogen Advances

Biogen will advance diranersen (BIIB080) to development after Phase 2 data showed tau biomarkers and slower cognitive decline.
The placebo-controlled CELIA trial, which enrolled 416 Alzheimer’s patients and missed its primary CDR-SB endpoint at Week 76, saw all doses cut CSF tau and PET signal.
Serious adverse events increased at the 115 mg dose, prompting the FDA to give Fast Track in 2025 and Biogen to present data at the July AAIC.

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