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# Biogen Defends Anti-Tau Alzheimer's Data After Investor Selloff
- URL: https://www.fdaweb.com/biogen-defends-anti-tau-alzheimers-data-after-investor-selloff/
- Published: 2026-07-14T12:00:00.000Z
- Updated: 2026-09-14T13:42:49.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5161454

Biogen executives sought to reassure investors Tuesday that its experimental anti-tau Alzheimer's disease therapy remains a promising late-stage candidate despite a sharp market selloff following detailed Phase 2 study results that raised questions about the drug's dose-response profile.

During an investor call held after the presentation of data from the Phase 2 CELIA trial at the Alzheimer's Association International Conference (AAIC) in London, Biogen executives argued that the study provides compelling evidence to advance diranersen into Phase 3 testing, even though the trial failed to meet its primary endpoint.

Shares of Biogen fell more than 8% as investors reacted to the data, with analysts expressing concern that the strongest clinical benefit was observed in patients receiving the lowest dose rather than higher doses — a finding that caused the study to miss its predefined endpoint based on a dose-dependent response. CELIA was designed with a primary endpoint of dose response on Clinical Dementia Rating Sum of Boxes at 18 months to investigate whether higher doses of diranersen could provide greater clinical benefit.

Company executives maintained that the results represent an important milestone for Alzheimer's research.