Biogen has presented phase 2 results for diranersen, an investigational tau-targeting treatment for Alzheimer’s disease, reporting reductions in cognitive decline across multiple clinical assessments and supporting plans to advance the drug into phase 3 development.
The findings were presented at the Alzheimer’s Association International Conference in London and came from the 18-month CELIA study, which enrolled 416 patients with early Alzheimer’s disease. Diranersen is an antisense oligonucleotide designed to reduce production of tau protein by silencing the MAPT gene responsible for its creation. Tau is one of the key proteins associated with Alzheimer’s disease and is closely linked to brain cell death and cognitive decline.
Researchers reported that the strongest results were observed in patients receiving the lowest tested dose of 60 mg administered into the spinal fluid every six months. Although the study did not meet its primary endpoint, which was based on demonstrating a dose-dependent treatment response, the lowest dose consistently produced the greatest benefit across several measures of cognition and disease progression.
At 18 months, patients in the 60 mg group experienced 26% less decline than placebo on the Clinical Dementia Rating Sum of Boxes assessment. The same group showed 42% less decline on the Alzheimer’s Disease Assessment Scale cognitive subscale and 50% less decline on the Mini Mental State Examination. Additional measures that combine cognitive and functional assessments also showed benefits, including a 30% slowing of decline on the modified Integrated Alzheimer’s Disease Rating Scale and a 23% slowing on the Alzheimer’s Disease Composite Score.
Brain imaging and spinal fluid analyses indicated a 50% to 65% reduction in tau levels across all studied doses. However, no significant difference versus placebo was observed on the ADCS-ADL-MCI scale, which evaluates daily functioning. Biogen said patients are continuing to be assessed on this measure through 24 months.
Cath Mummery, a professor of clinical neurology at University College London who led the study, said, “This trial, as far as I’m concerned, is proof of principle. If you change tau, you can change the course of the disease, and we haven’t had that before.”
Biogen’s head of Alzheimer’s clinical development, Szofia Bullain, said the consistency across multiple cognitive measures was reassuring, although she described the lack of improvement on the daily functioning assessment as puzzling. She said the company has working hypotheses regarding the finding and is continuing to evaluate the results.
The treatment differs from previous tau-targeting approaches that used antibodies. According to Ionis Pharmaceuticals, which originally developed diranersen before Biogen acquired full rights to the drug in 2019, diranersen suppresses production of tau by targeting the MAPT gene rather than attempting to remove toxic forms of tau after they have formed.
The study also reported no cases of amyloid-related imaging abnormalities (ARIA), a brain-swelling condition associated with some amyloid-targeting therapies. The most common adverse events were mild to moderate procedure-related effects, including headache, pain associated with lumbar puncture, and confusion that resolved quickly.
Biogen’s head of development, Dr. Priya Singhal, said the company is consulting Alzheimer’s specialists as it prepares a single pivotal phase 3 trial expected to begin in 2027, with data anticipated between 2030 and 2031. While Biogen has not yet selected a final dose for late-stage testing, company representatives indicated that the 60 mg dose distinguished itself in the phase 2 study.
Biogen has announced encouraging Phase 2 clinical trial results for its investigational therapy diranersen in patients with Alzheimer’s disease. The study demonstrated a reduction in cognitive decline, providing promising evidence that the treatment may help slow disease progression. These findings strengthen Biogen’s neuroscience pipeline and support the continued development of diranersen as a potential therapy for one of the world’s most challenging neurodegenerative disorders.
Positive Phase 2 Clinical Results
The Phase 2 study evaluated the safety, efficacy, and tolerability of diranersen in individuals with early-stage Alzheimer’s disease. According to Biogen, patients receiving the investigational therapy experienced slower cognitive decline compared with those in the control group.
Next Steps for Biogen
Following the encouraging Phase 2 data, Biogen is expected to continue evaluating diranersen through larger clinical trials designed to confirm efficacy, assess long-term safety, and support future regulatory submissions.
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