Stoke Therapeutics and Biogen present zorevunersen data at epilepsy meeting

Stoke Therapeutics Inc. (NASDAQ: STOK) and Biogen Inc. (NASDAQ: BIIB) presented data on zorevunersen, an investigational antisense oligonucleotide for Dravet syndrome, at the 2025 American Epilepsy Society Annual Meeting in Atlanta.

Long-term results from Phase 1/2a and open label extension studies showed seizure reductions and increased seizure-free days in patients treated with zorevunersen alongside standard anti-seizure medicines. The data also indicated improvements in cognition, behavior and quality of life.

A propensity score weighted analysis compared patients treated with zorevunersen to a matched cohort from the BUTTERFLY natural history study. Patients receiving two loading doses of zorevunersen (70mg) experienced statistically significant reductions in major motor seizure frequency at six months compared to natural history. With continued dosing at 45mg, improvements in cognition and behavior were shown at 18 months.

Electroencephalogram analysis showed dose-dependent effects of zorevunersen in decreasing abnormal brain activity. The analysis indicated that reduction in abnormal EEG activity was associated with increased probability of achieving meaningful seizure frequency reduction.

Safety data showed that 81 patients received at least one dose of zorevunersen, with more than 800 doses administered. Study drug related treatment emergent adverse events occurred in 30% of patients in Phase 1/2a studies and 53% in open label extension studies. The most common related adverse event was cerebrospinal fluid protein elevations. Three patient deaths were reported across studies, all assessed as unrelated to zorevunersen.

Zorevunersen is designed to treat Dravet syndrome by increasing functional NaV1.1 protein production from the non-mutated copy of the SCN1A gene. The drug has received orphan drug designation from the FDA and EMA, and breakthrough therapy designation from the FDA.

The companies are currently conducting the EMPEROR Phase 3 study, a global double-blind, sham-controlled trial evaluating zorevunersen in children ages 2 to less than 18 with Dravet syndrome.

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