Biogen, Stoke Therapeutics Ink Deal to Develop Zorevunersen for Dravet Syndrome

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Biogen and Stoke Therapeutics have reached an agreement to develop and commercialize zorevunersen, a potential first-in-class disease-modifying therapy for Dravet syndrome, in all regions outside of North America. Zorevunersen, an investigational antisense oligonucleotide that targets the SCN1A gene, was designed to treat the underlying cause of Dravet syndrome.¹

“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, MD, CEO, Stoke Therapeutics, in a press release. “Additionally, this collaboration provides cash flows, that when combined with Stoke’s financial position, support the company through to mid-2028.”

Under terms of the agreement, Stoke will lead global development and will retain exclusive development and commercialization rights in the United States. In turn, Biogen will receive the rights to commercialize zorevunersen in the rest of the world. Biogen will pay Stoke $165 million in an upfront payment, with the potential to receive up to $385 million in additional milestone and development payments. Stoke will pay 70% of external clinical development costs, with Biogen providing the additional 30%.

According to Biogen, approximately 38,000 people are currently living with Dravet syndrome in the United States, United Kingdom, European Union, and Japan.1 According to Orphanet, the average prevalence at birth is one in 30,000 newborns. An estimated 85% of all cases are a result of a mutation or deletion in the SCN1A gene. Most seizures related to Dravet syndrome begin between five and eight months of age in previously healthy infants.²

According to the Dravet Syndrome Foundation, individuals with Dravet syndrome will have a 15% to 20% chance of losing their lives as a result of sudden unexpected death in epilepsy, prolonged seizures, seizure-related accidents such as drowning, and infections.³

According to Stoke Therapeutics, over 90% of patients with Dravet syndrome suffer from at least one non-seizure comorbidity, such as severe intellectual disabilities; motor impairment; autism; sleep abnormalities; severe developmental disabilities; speech impairment; and behavior difficulties. Currently, there are around 20,000 people in the United States living with the condition. Further, an estimated one in 16,000 infants in the United States are born with Dravet syndrome.4 According to the National Organization for Rare Disorders, intellectual disabilities can manifest between 18 and 60 months after birth.⁵

Current treatments for the condition include valproic acid, GABA receptor agonists, glutamate blockers, stiripentol, and cannabidiol.⁴

“This collaboration broadens our late-stage pipeline with the addition of a Phase III-ready disease modifying investigational medicine and allows us to leverage our rare disease product commercialization expertise and global footprint,” said Priya Singhal, MD, MPH, head of development, Biogen, in the press release. “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.”

Moving forward, Stoke intends to initiate the Phase III EMPEROR registrational study in the second quarter of this year, with pivotal data expected in the second half of 2027 to support global regulatory filings.¹

References

1. Biogen and Stoke Therapeutics Enter into Collaboration to Develop and Commercialize Zorevunersen for the Treatment of Dravet Syndrome, a Rare Genetic Epilepsy Associated with Refractory Seizures and Neurodevelopmental Impairments. Biogen. February 18, 2025. Accessed February 20, 2025. https://investors.biogen.com/news-releases/news-release-details/biogen-and-stoke-therapeutics-enter-collaboration-develop-and

2. Dravet syndrome. Orphanet. Accessed February 20, 2025. https://www.orpha.net/en/disease/detail/33069#:~:text=Dravet%20syndrome%20Epidemiology%20The%20average%20prevalence%20at,diagnosis%20Genetic%20counseling%20Management%20and%20treatment%20Prognosis

3. What is Dravet Syndrome? Dravet Syndrome Foundation. Accessed February 20, 2025. https://dravetfoundation.org/what-is-dravet-syndrome/#:~:text=Dravet%20syndrome%20is%20a%20rare,the%20sodium%20channel%20gene%20SCN1A.

4. Dravet Syndrome Fact Sheet. Stoke Therapuetics. Accessed February 20, 2025. https://www.stoketherapeutics.com/wp-content/uploads/fact-sheet_dravet-syndrome_200605.pdf

5. Dravet Syndrome. NORD. Accessed February 20, 2025. https://rarediseases.org/rare-diseases/dravet-syndrome-spectrum/#diagnosis