Biogen said it will move diranersen into confirmatory Phase 3 after full Phase 2 CELIA data showed the 60 mg dose slowed decline by 26% on CDR-SB over 18 months versus placebo.
That dose also cut decline by 42% on ADAS-Cog13, 50% on MMSE, 30% on modified iADRS and 23% on ADCOMS, with most differences reaching nominal statistical significance.
Across all studied doses, diranersen reduced CSF total tau by 50-65% and lowered brain tau on PET, which Biogen said makes it the first tau-directed therapy to show both effects in a Phase 2 trial.
CELIA still missed its primary endpoint because higher doses did not produce greater benefit on CDR-SB, though all dose groups favored diranersen over placebo and no benefit emerged on ADCS-ADL-MCI at 18 months.
The 416-patient study found the intrathecal drug generally well tolerated, with mostly mild or moderate adverse events and more than 90% of completers entering the extension study.
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Biogen’s Diranersen Shows Robust Tau Reduction and Cognitive Gains in Phase 2 Alzheimer’s Trial, Advancing to Registrational Development
Overview
Biogen recently announced promising Phase 2 results for diranersen at the 2026 AAIC, marking a significant step forward in early Alzheimer’s disease treatment. The CELIA study showed that diranersen led to meaningful clinical improvements and a strong reduction in tau protein over 18 months. This dual impact on both symptoms and a key disease biomarker is encouraging for patients and researchers. The unprecedented combination of clinical and biomarker benefits has given Biogen the confidence to move diranersen into registrational development, with plans to work closely with regulators and the Alzheimer’s community on next steps.