Biogen Inc. (NASDAQ:BIIB) saw its stock climb about 2% on Tuesday after the company unveiled Phase 2 CELIA trial data for diranersen, its investigational therapy for Alzheimer’s disease.
Presented at the Alzheimer’s Association International Conference, the CELIA data indicated that diranersen produced clinical benefit and reductions in tau biomarkers across all doses evaluated at the 18-month mark. Biogen highlighted the 60 mg dose as showing the most pronounced clinical effect: a 42% slowing of decline on the ADAS-Cog13 cognitive scale and a 50% slowing on the MMSE cognitive measure, together with a 26% slowing on the CDR-SB functional endpoint.
According to the company, diranersen is the first tau-directed therapy in a Phase 2 study to show both lowered cerebrospinal fluid total tau and reduced brain tau pathology by PET imaging. Mean reductions in CSF total tau ranged between 50% and 65% across the studied doses, and PET measures of brain tau pathology decreased across doses as well.
Diranersen is an antisense oligonucleotide designed to target MAPT mRNA and thereby reduce production of all tau isoforms. On the basis of the Phase 2 findings, Biogen announced plans to progress the candidate into Phase 3 development.
The CELIA trial enrolled 416 participants with early Alzheimer’s disease and tested three dose levels of diranersen, each administered intrathecally over an 18-month period. The company reported that the study did not meet its primary endpoint of a dose-response relationship on the CDR-SB at 18 months.
Safety findings showed diranersen was generally well tolerated; most adverse events were described as mild or moderate. The most commonly reported events were procedural pain, post-lumbar puncture syndrome, and confusional state. More than 90% of participants who completed the placebo-controlled portion of the trial chose to continue into the extension study.
The U.S. Food and Drug Administration granted Fast Track designation to diranersen for the treatment of Alzheimer’s disease in 2025.
Contextual note: The stock movement followed the presentation of the CELIA results; Biogen intends to advance diranersen into later-stage testing based on the data described above.