Stoke Therapeutics and Biogen to present four-year zorevunersen data at epilepsy congress

Stoke Therapeutics (NASDAQ:STOK) and Biogen (NASDAQ:BIIB) said they will present clinical data for zorevunersen, their investigational treatment for Dravet syndrome, at the 16th European Epilepsy Congress in Athens, Greece, from September 5 to 9.

The presentations will include the first disclosure at a medical meeting of four-year results from ongoing Phase 1/2a open-label extension studies.

According to the companies, improvements in cognition and behaviour were sustained through four years alongside reductions in seizures and a generally well-tolerated safety profile. New sub-analyses will also examine the treatment’s effects on the most severe seizure types and patient quality of life.

These findings are based on company-reported clinical data and zorevunersen remains investigational.

Majority of patients remain in extension studies

A total of 81 patients were enrolled in the Phase 1/2a studies, with 93% subsequently continuing into one of two open-label extension studies.

At the four-year data cutoff, 77% of those patients remained enrolled.

More than 930 doses of zorevunersen had been administered as of July 31, 2026.

Elevated cerebrospinal fluid protein levels were observed in approximately 94% of patients, with 59% classified as treatment-emergent adverse events. According to Stoke and Biogen, no serious clinical manifestations or cases of hydrocephalus were reported.

The clinical significance of the reported findings remains subject to further evaluation, including results from ongoing late-stage development.

Zorevunersen targets the SCN1A gene

Zorevunersen is an antisense oligonucleotide designed to increase production of functional NaV1.1 protein by targeting the unaffected copy of the SCN1A gene. Mutations in SCN1A are associated with most cases of Dravet syndrome.

The investigational therapy has received Breakthrough Therapy Designation from the U.S. Food and Drug Administration, as well as orphan drug designation from both the FDA and the European Medicines Agency.

These designations are intended to support the development of qualifying treatments and do not constitute regulatory approval.

Phase 3 EMPEROR study underway

Stoke Therapeutics and Biogen are currently evaluating zorevunersen in the global Phase 3 EMPEROR study, with results anticipated in the third quarter of 2027.

The timing represents the companies’ current expectation and remains subject to the progress of the clinical trial.

Under the companies’ collaboration agreement, Stoke retains commercialization rights for zorevunersen in the United States, Canada and Mexico, while Biogen holds exclusive rights in the rest of the world.

Zorevunersen has not been approved by any regulatory authority, and its safety and efficacy remain under clinical investigation.

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