Diranersen (IONIS-MAPTRx/BIIB080) - (CELIA)

July 14, 2026: Biogen Inc. (NASDAQ: BIIB) presented additional Phase 2 CELIA study data at AAIC 2026 for diranersen (BIIB080), an investigational intrathecal antisense oligonucleotide targeting MAPT mRNA, in early Alzheimer’s disease. At 18 months, the 60 mg every-six-months arm (n=60) showed the largest clinical effects vs placebo (n=115), including 0.54-point (26%) slowing on CDR-SB, 42% on ADAS-Cog13, 50% on MMSE, 30% on modified iADRS, and 23% on ADCOMS; most differences were nominally statistically significant. Other dose regimens (115 mg q6mo; 115 mg q3mo) also favored diranersen on CDR-SB (14% and 9% slowing) and other cognitive/composite endpoints. However, CELIA did not meet its primary endpoint (dose response on CDR-SB at Week 76), and higher doses were not associated with greater slowing.

Biomarkers showed mean CSF total tau reductions of 50–65% across doses; a tau PET substudy (n=131) showed decreases across evaluated brain regions. No separation vs placebo was observed on ADCS-ADL-MCI at 18 months; longer follow-up continues. Biogen said diranersen was generally well tolerated and plans to advance it into confirmatory Phase 3 development; an ongoing long-term extension is underway. The FDA granted Fast Track designation in 2025.