Biogen & Stoke's RNA Drug Aims to Disrupt Dravet Syndrome Treatment

BEDFORD, MA – December 01, 2025 – In the high-stakes world of rare disease therapeutics, a simple press release can signal a seismic shift. The latest tremor comes from a strategic alliance between biotech giant Biogen and RNA medicine specialist Stoke Therapeutics, who have announced a series of crucial data presentations for their investigational drug, zorevunersen. As the epilepsy community prepares for the 2025 American Epilepsy Society (AES) Annual Meeting, the new findings promise to offer the most detailed look yet at a therapy that aims not just to manage, but to fundamentally alter the course of Dravet syndrome.

This isn't just another drug announcement. It represents a potential pivot in treating a devastating genetic disorder. For years, the therapeutic strategy for Dravet syndrome—a severe developmental and epileptic encephalopathy—has been a defensive battle focused on managing relentless seizures. Zorevunersen, an antisense oligonucleotide (ASO), is designed for offense, targeting the underlying genetic flaw that causes the disease. The upcoming presentations, which will feature four years of long-term clinical data, are poised to provide compelling evidence of its potential as a true disease-modifying therapy, a term that carries immense weight for patients, clinicians, and investors.

A New Mechanism for a Devastating Disease

Dravet syndrome is more than just epilepsy. Caused primarily by a mutation in one copy of the SCN1A gene, the condition leads to a deficiency of a critical protein, NaV1.1, in the brain's neurons. This insufficiency triggers not only frequent, debilitating seizures but also a cascade of severe cognitive, behavioral, and motor impairments. The risk of Sudden Unexpected Death in Epilepsy (SUDEP) is tragically high, with up to 20% of children not surviving to adulthood.

Existing treatments, such as fenfluramine (Fintepla) and cannabidiol (Epidiolex), have provided meaningful reductions in seizure frequency for many. However, they are fundamentally symptomatic treatments. They work to dampen the downstream effects of the genetic defect but do not correct the core problem. Furthermore, they can come with significant side effects and rarely achieve complete seizure freedom, leaving the profound neurodevelopmental issues largely unaddressed.

This is where zorevunersen represents a market disruption. Leveraging Stoke's proprietary TANGO (Targeted Augmentation of Nuclear Gene Output) platform, the ASO is designed to bind to the messenger RNA (mRNA) from the healthy, non-mutated copy of the SCN1A gene. This action increases the production of functional NaV1.1 protein, aiming to restore levels closer to normal. In theory, this upstream intervention could not only control seizures more effectively but also mitigate or even reverse the associated cognitive and behavioral deficits.

“Our four years of data showing substantial and durable effects on seizures, behavior and cognition, combined with our ability to compare directly to natural history data, allow us to more fully appreciate the disease-modifying potential of zorevunersen for the treatment of Dravet syndrome,” stated Barry Ticho, M.D., Ph.D., Chief Medical Officer of Stoke Therapeutics. This statement underscores the confidence that the therapy is impacting the disease's natural history, not just its symptoms.

Beyond Seizure Counts: Redefining Clinical Success

The data set for AES promises to move the conversation beyond the traditional endpoint of seizure reduction. While durable seizure control is a cornerstone of the findings, Biogen and Stoke are highlighting evidence that points to a much broader, more holistic impact on patients.

One of the most compelling new datasets involves electroencephalogram (EEG) analyses. Abnormal brain activity is a hallmark of Dravet syndrome. According to Katherine Dawson, M.D., Head of the Therapeutics Development Unit at Biogen, exploratory analyses show that zorevunersen treatment is associated with a decrease in this abnormal activity. “In patients treated with zorevunersen, exploratory analyses showed that a reduction in abnormal brain EEG activity was associated with an increased probability of achieving a reduction in major motor seizure frequency,” she explained. This electrophysiological evidence provides a biological underpinning for the clinical benefits observed, suggesting the therapy is normalizing brain function at a fundamental level.

The presentations will also detail improvements in quality of life, overall functioning, and specific behavioral and cognitive domains. For families navigating the daily challenges of Dravet, progress in communication, interpersonal skills, and personal independence can be as life-changing as a reduction in seizures. This focus on comprehensive well-being aligns with the immense unmet need articulated by patient advocacy groups, who have long called for treatments that offer hope for a better developmental trajectory.

The Strategic Blueprint for a Niche Blockbuster

The partnership between Biogen and Stoke is a textbook example of modern biopharma strategy. Stoke, the agile innovator with a groundbreaking RNA platform, provides the scientific engine. Biogen, with its deep pockets, global commercial infrastructure, and decades of experience in neurology, provides the horsepower to navigate late-stage development and global market access.

The commercialization agreement is particularly shrewd. Stoke retains rights in the key North American markets (U.S., Canada, Mexico), allowing it to build its own commercial presence and capture the full value in its home territory. Biogen secures rights for the rest of the world, leveraging its established international network to bring zorevunersen to a global patient population estimated at up to 38,000 across major markets.

This structure de-risks the venture for both parties. Stoke gains a significant partner to fund the costly final stages of development, including the pivotal Phase 3 EMPEROR study, while Biogen adds a high-potential, first-in-class asset to its neurology pipeline. Given the premium pricing commanded by transformative rare disease therapies, zorevunersen could become a significant revenue driver for both companies if approved, despite the relatively small patient population.

While the competitive landscape is not static—with therapies like Takeda's soticlestat also in late-stage trials—zorevunersen's unique, disease-modifying mechanism gives it a powerful differentiating narrative. The upcoming AES data will be critical in solidifying this narrative. If the long-term results confirm that zorevunersen can durably improve cognition and behavior while controlling seizures, it could set a new standard of care, transforming the therapeutic landscape and, more importantly, the lives of thousands of families affected by Dravet syndrome.