Biogen and Stoke Show Long-Term Data Supporting Zorevunersen’s Disease-Modifying Potential in Dravet Syndrome — Biogen Inc.

Event summary

4-year data from Phase 1/2a open-label extension studies show durable reductions in seizures and improvements in cognition and behavior for Dravet syndrome patients treated with zorevunersen.
New sub-analysis reveals substantial reductions in severe seizure types, a leading risk factor for sudden unexpected death in epilepsy (SUDEP).
Quality of life improvements demonstrated through 28 months of treatment, with zorevunersen generally well tolerated over 5 years.
Phase 3 EMPEROR study data anticipated in Q3 2027 to complete rolling U.S. NDA submission to the FDA.

The big picture

Biogen and Stoke Therapeutics’ long-term data on zorevunersen highlight the potential for a first-in-class disease-modifying treatment for Dravet syndrome, a severe developmental and epileptic encephalopathy with no approved therapies. The collaboration between Biogen and Stoke, with Biogen holding exclusive rest-of-world commercialization rights, positions the partnership to address a significant unmet need in rare neurological diseases. The upcoming Phase 3 data readout will be critical in determining the regulatory and commercial trajectory of zorevunersen.

What we're watching

Regulatory Pathway: Whether the Phase 3 EMPEROR study results in Q3 2027 will support a successful rolling NDA submission to the FDA by the second half of 2027.
Clinical Efficacy: The durability of zorevunersen’s disease-modifying effects beyond the 4-year data cutoff, particularly in reducing severe seizures and improving neurodevelopmental outcomes.
Commercial Strategy: How Biogen and Stoke Therapeutics will position zorevunersen in the market if approved, given the lack of current disease-modifying therapies for Dravet syndrome.