Biogen Inc. (Nasdaq: BIIB) today announced data from the Phase 2 CELIA study evaluating diranersen, an investigational antisense oligonucleotide (ASO) therapy targeting tau, in individuals with early Alzheimer’s disease. The data, presented at the Alzheimer’s Association International Conference (AAIC) 2026, expand upon previously reported topline results and demonstrate a combination of meaningful clinical efficacy and robust biomarker effects, providing Phase 2 proof of concept for diranersen’s tau-directed mechanism of action. Based on the growing and consistent body of evidence from the Phase 1b and Phase 2 studies, Biogen plans to advance diranersen into confirmatory Phase 3 development.

Diranersen demonstrated efficacy across all studied doses at 18 months, with consistent efficacy across multiple prespecified secondary endpoints, including the Clinical Dementia Rating Sum of Boxes (CDR-SB), a global measure of cognition and daily function; ADAS-Cog13 and MMSE, measures of cognition; modified iADRS and ADCOMS, composite measures of cognition, function, and disease progression; as well as the individual cognitive and functional domains of CDR-SB. Diranersen 60 mg administered intrathecally every six months (n=60) showed the strongest response at 18 months. Compared with placebo (n=115), diranersen 60 mg demonstrated slowing of clinical decline by 0.54 points (26%) on CDR-SB; 42% on ADAS-Cog13; 50% on MMSE; 30% on modified iADRS; and 23% on ADCOMS. The majority of these endpoint differences achieved nominal statistical significance compared with placebo.