Investing.com -- Biogen Inc. (NASDAQ: BIIB) shares rose 10% Thursday after the company reported positive results from its Phase 2 CELIA study of diranersen, an experimental Alzheimer’s treatment targeting tau protein.

The study showed robust reductions in tau pathology across all doses tested, with results consistent with an earlier Phase 1b trial. Pre-specified analyses of cognitive endpoints demonstrated slowing of clinical decline across all studied doses, particularly at the lowest dose of 60 mg administered every 24 weeks.

Diranersen demonstrated reductions in both cerebrospinal fluid tau and tau pathology measured by positron emission tomography across all doses, with reductions maintained throughout the dosing period. The study did not meet its primary endpoint assessing dose response for change from baseline on the Clinical Dementia Rating–Sum of Boxes at Week 76.

The 18-month study enrolled 416 participants with mild cognitive impairment due to Alzheimer’s disease or mild Alzheimer’s disease dementia who had not previously received anti-amyloid therapy. Three doses were evaluated: 60 mg every 24 weeks, 115 mg every 24 weeks, and 115 mg every 12 weeks.

The safety and tolerability profile was generally consistent with the Phase 1b study. The incidence of adverse events was comparable across dose groups, with a higher incidence of serious adverse events observed at the highest dose.

Biogen said it plans to advance diranersen to registrational development and will engage with regulators on next steps. The U.S. Food and Drug Administration granted Fast Track designation to diranersen for the treatment of Alzheimer’s disease in 2025.

Diranersen is an antisense oligonucleotide designed to reduce tau protein production. Unlike approaches targeting extracellular tau, diranersen is designed to reduce both extracellular and intracellular tau. Data will be presented at the Alzheimer’s Association International Conference in 2026.