Biogen Presents Long-Term Dravet Syndrome Data

Biogen and partner Stoke Therapeutics presented long-term clinical data on 3 September 2026 for zorevunersen, an investigational medicine for Dravet syndrome. The findings were shared at the 16th European Epilepsy Congress in Athens, Greece, covering more than five years of clinical experience.

Four-year open-label extension data showed durable seizure reductions along with statistically significant improvements in cognition and behavior at one, two, three and four years. Following initial Phase 1/2a trials, 93% or 75 of 81 eligible patients entered the extension studies, and 77% or 58 of 75 patients remained enrolled at the four-year cutoff. Patients also demonstrated quality of life gains through 28 months.

The drug remained generally well tolerated, with more than 930 doses administered as of 31 July 2026. Elevated cerebrospinal fluid protein lab values occurred in approximately 94% of patients, with 59% classified as treatment-emergent adverse events, though no serious clinical manifestations or cases of hydrocephalus were reported.

Biogen expects Phase 3 data from the pivotal EMPEROR trial in the third quarter of 2027. The trial completed primary enrollment with 162 patients across the United States, the United Kingdom and Japan, alongside 34 participants in Europe. The readout will support a planned rolling application to the U.S. Food and Drug Administration in the second half of 2027.