Biogen presented results from the Phase II CELIA study of diranersen, an investigational tau-targeting antisense oligonucleotide, in people with early Alzheimer's disease (AD) at the Alzheimer's Association International Conference (AAIC) 2026, held in London from 12–15 July.
The randomised, double-blind and placebo-controlled study enrolled 416 participants with mild cognitive impairment due to AD or mild AD dementia. Participants received intrathecal diranersen at one of three dose regimens—60 mg every six months, 115 mg every six months or 115 mg every three months—over an 18-month placebo-controlled treatment period.
As previously disclosed, CELIA did not meet its primary endpoint of demonstrating a dose-response relationship for change from baseline on the Clinical Dementia Rating–Sum of Boxes (CDR-SB) at Week 76. However, the lowest dose (60 mg every six months) showed the greatest clinical benefit, slowing decline by 26% on CDR-SB, 42% on ADAS-Cog13 and 50% on MMSE compared with placebo. Clinical benefits were also observed with the two higher-dose regimens across multiple prespecified endpoints.
Across all dose groups, diranersen demonstrated robust reductions in tau pathology. According to Biogen, diranersen is the first tau-directed therapy to demonstrate robust reductions in both cerebrospinal fluid (CSF) total tau, with mean reductions of 50–65%, and brain tau pathology, as measured by PET, across all studied doses in a Phase II study.
Additional analyses from the CELIA study and its ongoing long-term extension trial will be presented at future scientific conferences. Based on the Phase Ib and Phase II findings, the company plans to advance diranersen into confirmatory Phase III development.
https://investors.biogen.com/news-releases/news-release-details/biogen-presents-phase-2-celia-data-aaic-demonstrating-meaningful
