Biogen has secured rights to market a promising experimental epilepsy treatment outside North America through a new collaboration with Stoke Therapeutics, marking another strategic move to bolster its rare disease portfolio.
The agreement, announced February 18, 2025, involves an upfront payment of $165 million from Biogen to gain exclusive
commercialization rights for zorevunersen in territories beyond the United States, Canada, and Mexico. The deal structure includes potential additional payments of up to $385 million tied to
development and commercial milestones, along with a 30-70 split of external development costs between the companies.
Zorevunersen, which could become a first-in-class therapy for Dravet syndrome, is preparing to enter Phase 3 clinical trials this year, with results anticipated in 2027. The drug represents a novel approach as an antisense oligonucleotide designed to increase sodium channel protein expression linked to the rare epilepsy condition.
The partnership comes at a crucial time for Biogen, which has experienced declining revenues over recent years from its established products like Spinraza and multiple sclerosis treatments. Under CEO Christopher Viehbacher’s leadership since late 2022, the company has actively pursued external growth opportunities, including the $7.3 billion acquisition of Reata Pharmaceuticals and a $1.2 billion deal for HI-Bio.
Stifel analyst Paul Matteis views the agreement as strategically sound, noting Biogen’s existing presence in rare neurological disorders through products like Spinraza and Skyclarys. The relatively modest upfront investment could yield significant returns if zorevunersen proves successful, though Matteis acknowledges the drug faces high efficacy expectations from physicians.
Market research suggests strong potential for the treatment, with a TD Cowen survey of 25 epilepsy specialists indicating 60% saw
zorevunersen as superior to current Dravet syndrome therapies. However, challenges remain, including the drug’s intravenous administration in a market dominated by oral medications and potential pricing pressures outside the U.S.
Recent clinical data has shown promise, with a small study
demonstrating superior seizure reduction at high doses compared to placebo in Dravet syndrome patients. Stoke has already aligned with regulators in the U.S., Europe, and Japan on the design of its upcoming Phase 3 trial.
The condition affects an estimated 38,000 people across major markets including the U.S., U.K., Japan, and several European countries, according to Biogen’s assessment. Zorevunersen’s mechanism of action targets specific RNA sequences to enhance the expression of sodium channel proteins, which play crucial roles in brain function and have been identified as potential therapeutic targets for various neurological conditions.
The agreement also includes provisions for Biogen to potentially license rights to related products that work through similar mechanisms as zorevunersen. While Wall Street’s reaction was muted, with Biogen’s shares showing little movement following the
announcement, analysts view the deal as a logical fit within the company’s portfolio strategy, though not one that will significantly impact near-term investment prospects.
Stoke’s successful regulatory discussions have established a clear path forward for zorevunersen’s late-stage development, with harmonized trial designs agreed upon across major markets. This positions the drug for potential global commercialization, pending positive clinical results in the coming years.