A New Drug Cuts Seizures by 91% in Dravet Syndrome — One of Childhood Epilepsy’s Most Devastating Forms

A Genetic Fix for a Genetic Crisis

Some children wake up seizing dozens of times before breakfast. Others experience status epilepticus—prolonged seizures lasting minutes or hours—triggered by nothing more than a slight fever. This is Dravet syndrome, a rare genetic epilepsy that strikes infants without warning, derails development, and resists most drugs. Now, for the first time, a treatment targets the genetic root cause.

A clinical trial published this week in The New England Journal of Medicine shows that zorevunersen, an antisense oligonucleotide developed by Stoke Therapeutics and Biogen, reduced seizures by as much as 91% in children with Dravet syndrome. For families managing a seizure burden that can exceed 17 per month, this represents not just a breakthrough—it represents the first disease-modifying treatment for a condition previously considered largely untreatable.

The Burden: Why Dravet Syndrome Matters

Dravet syndrome affects approximately 1 in 15,700 newborns. It emerges suddenly, usually within the first year of life, often triggered by fever. The first seizure may last more than five minutes and can progress to status epilepticus. What follows is a childhood defined by seizure fear: some children experience dozens of seizures weekly, every week.

The culprit is a mutation in the SCN1A gene, which codes for Nav1.1, a protein critical for allowing brain cells to communicate via electrical signals. In Dravet, this mutation doesn’t cause overactive neurons—it causes a deficit. The brain simply doesn’t produce enough functional Nav1.1. This is a loss-of-function disorder at the molecular level.

Current treatments address only the symptom: seizures. Doctors prescribe antiseizure medications, sometimes a cocktail of them, but most children with Dravet remain treatment-resistant. They continue seizing despite medication. Schools become difficult; development slows. Families exhaust both their medical options and their emotional reserves.

The Mechanism: Genetic Medicine, Explained

Zorevunersen operates differently from conventional seizure drugs. It’s an antisense oligonucleotide—a short strand of synthetic genetic code, roughly 20 molecules long—designed to slip into the brain and modulate how the SCN1A gene is read and translated into protein.

Specifically, zorevunersen binds to a particular section of the SCN1A messenger RNA, causing the cell’s machinery to skip a faulty exon (a segment of the genetic code). This skipping allows the ribosome to read past the mutation and produce functional, full-length Nav1.1 protein. The mutated copies remain broken, but now the cell also makes working copies—enough to restore proper neural communication.

This represents a fundamental shift in epilepsy treatment: from dampening all seizures chemically to fixing the genetic root cause in precise populations. Zorevunersen is not for all epilepsy. It works because it targets the specific molecular defect in Dravet.

The Data: What 91% Reduction Means

In the Phase 1/2a trial, 81 children aged 2–18 with confirmed SCN1A mutations received intrathecal doses of zorevunersen (injected directly into the cerebrospinal fluid around the brain and spinal cord). Over the subsequent months, researchers tracked seizure frequency.

The results:

• Median seizure reduction: 91% across one-month intervals in the extension studies
• Detailed response: Patients receiving two or three 70 mg doses achieved 85% reduction at three months and 74% at six months, with some maintaining or improving upon this for up to 36 months
• Safety: The drug was well tolerated. The most common adverse events were elevated cerebrospinal fluid protein and post-lumbar puncture syndrome—expected from the delivery method, not the drug itself

Beyond seizures, trials tracked secondary endpoints. Children showed improvements in overall clinical status, quality of life, and adaptive behavior. Some seized less; others seized much less. Individual responses varied—not every child achieved the 91% figure—but the range was striking.

For context: the trial population averaged 17 seizures per month at baseline. A 91% reduction translates to roughly 1.5 seizures per month. For many families, this shift from double-digit weekly seizures to rare seizures is transformative.

What Comes Next: From Proof to Prescription

Zorevunersen is not yet approved. The Phase 1/2a data represents proof of concept. Stoke and Biogen are currently running the EMPEROR study, a larger Phase 3 trial involving approximately 150 children at roughly 60 sites worldwide. This double-blind, sham-controlled trial will definitively establish efficacy in a broader population.

Enrollment is expected to complete in the second quarter of 2026. Data should emerge by mid-2027, with a rolling New Drug Application (NDA) submission to the FDA expected in early 2027. If approved, zorevunersen could become available as early as 2027 or 2028.

Approval, when it comes, will mark a watershed moment: the first genetic medicine specifically designed to modify the disease course of Dravet syndrome. It also signals a broader trend in pediatric neurology—a shift toward precision genetic medicines for previously untreatable childhood neurological conditions.

A Rare Moment

One in 15,700 children is born with Dravet syndrome. Some live with the hope that their child will outgrow it (rare, but possible). Most live with vigilance, medication adjustments, specialized schools, and the specter of SUDEP—sudden unexpected nocturnal death in epilepsy, which carries a real risk in severe, uncontrolled Dravet.

Zorevunersen doesn’t promise a cure. Individual responses will vary. But for families managing a seizure disorder that has resisted nearly everything, a drug that addresses the genetic root and demonstrates a 91% seizure reduction offers something they have not had: genuine hope based on genetic precision.

The trial data arrives this week. The larger trial progresses. And for Dravet families watching closely, one message is clear: the untreatable is becoming treatable.

Sources

• The New England Journal of Medicine. Zorevunersen in Children and Adolescents with Dravet Syndrome (March 2026)
• Stoke Therapeutics and Biogen press releases, March 2026
• Dravet Syndrome Foundation: What is Dravet Syndrome, genetics and epidemiology resources
• ScienceDaily: “New drug cuts seizures by up to 91% in children with rare epilepsy” (March 4, 2026)
• Medical Xpress: “First gene regulation clinical trials for epilepsy show promising results” (March 2026)