Biogen has collaborated with Stoke Therapeutics 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 United States, 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 recently announced plans to initiate a global Phase 3 registrational study of zorevunersen (EMPEROR) following successful alignment with regulatory agencies in the United States, Europe, and Japan. The study is on track to initiate in the second quarter of 2025, with a pivotal data readout expected in the second half of 2027, which is anticipated to support global regulatory filings.

Significant unmet treatment needs remain for patients with Dravet syndrome, 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 is difficult to treat and has a poor long-term prognosis. Currently, it is estimated that up to 38,000 people are living with Dravet syndrome in the U.S., UK, EU-4 and Japan.

“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.

“Additionally, this collaboration provides cash flows, that when combined with Stoke’s financial position, support the company through to mid-2028,” added Kaye.

“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.

“The reductions in seizures in patients already receiving standard of care medicines, together with the improvements in multiple measures of cognition and behavior, demonstrate the potential of zorevunersen as the first disease modifying medicine that addresses the underlying cause of Dravet syndrome,” added Singhal.

Stoke will continue to lead global development and retains exclusive development and commercialization rights for zorevunersen in the United States, 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 USD 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 tiered royalties ranging from low double digits to high teens on potential net sales in the Biogen territory.

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

Zorevunersen has been granted FDA Breakthrough Therapy Designation based on preliminary clinical evidence indicating that the drug may demonstrate substantial improvement over available therapy on clinically-significant endpoint(s).

Data from Phase 1/2a and open-label extension (OLE) studies of zorevunersen showed that patients treated with zorevunersen experienced substantial and durable reductions in convulsive seizure frequency and improvements in multiple measures of cognition and behavior, which support advancement to a global registrational Phase 3 study with potential for disease modification. Zorevunersen has been generally well tolerated across the studies.