Biogen and Stoke Therapeutics have announced a partnership aimed at advancing a disease-modifying treatment for Dravet syndrome, with the deal worth $550m.
Up to 38,000 people in the US, UK, EU and Japan are estimated to be living with Dravet syndrome, a genetic developmental and epileptic encephalopathy characterised by recurrent seizures, as well as significant cognitive and behavioural impairments.
There are currently no disease-modifying therapies approved for the condition, which is difficult to treat and has a poor long-term prognosis.
Stoke’s zorevunersen is an investigational antisense oligonucleotide (ASO) that targets the SCN1A gene, the underlying cause of most cases of Dravet syndrome, to reduce seizure frequency beyond what has been achieved with anti-seizure medicines and improve neurodevelopment, cognition and behaviour.
The candidate has already been granted Breakthrough Therapy Designation by the US Food and Drug Administration, and Stoke recently announced plans to initiate a global phase 3 registrational study of the drug.
Stoke will continue to lead zorevunersen’s global development and will retain exclusive development and commercialisation rights for the drug in the US, Canada and Mexico, while Biogen will gain exclusive commercialisation rights in the rest of the world.
Under the terms of the agreement, Biogen will contribute to 30% of the external clinical development costs and Stoke will receive an upfront payment of $165m, up to $385m in development and commercial milestone payments, as well as tiered royalties in Biogen’s territory.
Biogen has also been given the option to licence rights outside of the US, Canada and Mexico to certain future follow-on ASO products targeting SCN1A, in exchange for separate milestones, cost sharing and royalty considerations.
Priya Singhal, head of development at Biogen, said: “The reductions in seizures in patients already receiving standard-of-care medicines, together with the improvements in multiple measures of cognition and behaviour, demonstrate the potential of zorevunersen as the first disease-modifying medicine that addresses the underlying cause of Dravet syndrome.”
Stoke’s chief executive officer, Edward Kaye, added: “With Biogen’s… experience in neurology and track record of success in commercialising… 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.”