Biogen and Stoke Therapeutics entered a collaboration for the development and commercialization of zorevunersen, a potential first-in-class disease modifying medicine in development for the treatment of Dravet syndrome, in all territories outside the U.S., Canada, and Mexico. Zorevunersen is an investigational antisense oligonucleotide (ASO) that targets the SCN1A gene, the underlying cause of most cases of Dravet syndrome. 

Stoke plans to initiate a global Phase 3 registrational study of zorevunersen (EMPEROR) in the U.S., Europe, and Japan in 2Q25, with a data readout expected 2H27, which is anticipated to support global regulatory filings.

Dravet syndrome is a severe, genetic developmental and epileptic encephalopathy characterized by severe, recurrent seizures as well as significant cognitive and behavioral impairments. There are no approved disease-modifying therapies for Dravet syndrome, which impacts as many as 38,000 people in the U.S., UK, EU-4 and Japan.

Stoke will continue to lead global development and retains exclusive development and commercialization rights for zorevunersen in the U.S., Canada, and Mexico. Biogen receives exclusive rights to commercialize zorevunersen in the rest of the world. Upon closing of this transaction, Stoke will receive an upfront payment of $165 million. The parties will share external clinical development costs for zorevunersen (30 percent Biogen; 70 percent Stoke). Additionally, Stoke may receive up to $385 million in development and commercial milestone payments. Stoke will also be eligible to receive royalties on potential sales in the Biogen territory.

“With Biogen’s deep experience in neurology and track record of success in commercializing high-value disease-modifying medicines for rare genetic diseases globally, we aim to lead the treatment of Dravet syndrome into a new era by delivering zorevunersen to all patients who could benefit,” said Edward M. Kaye, M.D., Chief Executive Officer of Stoke Therapeutics.

“This collaboration broadens our late-stage pipeline with the addition of a Phase 3-ready disease modifying investigational medicine and allows us to leverage our rare disease product commercialization expertise and global footprint,” said Priya Singhal, M.D., M.P.H., Head of Development at Biogen.

Stoke has also granted Biogen an option to license rights outside of the U.S., Canada, and Mexico to certain future follow-on ASO products targeting SCN1A, in exchange for separate milestone, cost sharing, and royalty considerations.