Biogen has entered into a licensing agreement with Stoke Therapeutics, securing rights to market the experimental epilepsy treatment zorevunersen in regions outside North America. The deal, announced on February 18, 2025, involves an upfront payment of $165 million to Stoke, with potential additional payments of up to $385 million tied to development and commercial milestones.
The agreement grants Biogen exclusive commercialization rights for zorevunersen in territories beyond the United States, Canada, and Mexico. The companies will share external development costs at a 30-70 split, and Biogen has secured options to license related follow-on products that utilize similar mechanisms of action.
Zorevunersen, which targets Dravet syndrome, is positioned to begin Phase 3 clinical trials this year, with results anticipated in 2027. The drug represents a potential breakthrough as a first-of-its-kind treatment for this rare form of epilepsy, which affects approximately 38,000 individuals across the U.S., U.K., Japan, and several European markets, according to Biogen’s estimates.
The collaboration comes at a strategic time for Biogen, whose revenue has been declining over recent years, with further decreases projected for 2025. Under CEO Christopher Viehbacher’s leadership since late 2022, the company has actively pursued acquisitions, including the $7.3 billion purchase of Reata Pharmaceuticals and a $1.2 billion deal for HI-Bio.
Stifel analyst Paul Matteis views the acquisition as aligned with Biogen’s focus on rare neurological disorders, complementing their existing portfolio which includes Spinraza and Skyclarys. While the upfront investment is considered modest relative to zorevunersen’s potential market value, success hinges on positive Phase 3 trial outcomes.
The drug, classified as an antisense oligonucleotide, functions by binding to specific RNA sequences to enhance the expression of a sodium channel protein linked to Dravet syndrome. Recent clinical data has shown promise, with high-dose administration demonstrating significant reduction in convulsive seizures compared to placebo in early studies.
However, market analysts point out potential challenges. The intravenous administration requirement could pose difficulties in a market dominated by oral medications. Additionally, pricing strategies outside the U.S. may be complicated by the modest pricing success of other seizure treatments like Epidiolex and Fintepla in international markets.
A TD Cowen survey of 25 epilepsy specialists revealed that 60% considered zorevunersen more promising than existing Dravet syndrome treatments. However, physicians emphasize that the drug must meet substantial efficacy standards in late-stage testing to succeed.
Stoke has recently secured agreements with regulatory authorities in the United States, Europe, and Japan regarding the design of its upcoming Phase 3 trial. The study focuses on sodium channels, which are crucial cellular components throughout the body, particularly in the brain, and have long been considered valuable targets for treating various neurological conditions including epilepsy, pain, and mood disorders.
The market response to the announcement was measured, with Biogen’s stock showing minimal movement in morning trading following the news. While analysts view the deal as strategically sound, they suggest it’s unlikely to significantly impact Biogen’s investment outlook in the immediate future, similar to their assessment of the company’s previous attempt to acquire Sage Therapeutics.