For children with Dravet syndrome, seizures are not an occasional disruption. They are a constant, life-defining presence — beginning in the first year of life, resistant to almost every medication tried, sometimes lasting hours, and capable of leaving lasting neurological damage with each episode. The condition affects around 1 in 15,000 children. It has no cure. Its management, for most families, means a revolving door of anticonvulsants that offer partial relief at best.
Results published in March 2026 offer the most compelling evidence yet that this may be about to change.
A Phase 1/2a clinical trial of **zorevunersen** (also known as STK-001), an experimental drug developed by Stoke Therapeutics in partnership with Biogen, has demonstrated seizure reductions of **59% to 91%** in children with Dravet syndrome — across a 20-month follow-up period. The drug appears to be safe. It is well-tolerated. And its mechanism targets the fundamental genetic cause of the condition rather than merely dampening symptoms.
**What Dravet Syndrome Is**
Dravet syndrome is a rare, severe form of genetic epilepsy caused by mutations in the **SCN1A gene** — the gene responsible for producing a protein called NaV1.1, which regulates electrical signalling in neurons. When SCN1A is faulty, neurons misfire. The result is severe, treatment-resistant seizures, often triggered by heat or fever, beginning in infancy.
Beyond seizures, Dravet syndrome causes developmental delays, cognitive impairment, and behavioural difficulties. Many children require constant supervision. Life expectancy is reduced. The unpredictability of seizures means that families live in a state of permanent vigilance.
Existing medications — valproate, clobazam, stiripentol, fenfluramine — can reduce seizure frequency but rarely eliminate them. They work by suppressing seizure activity generally, rather than addressing the underlying NaV1.1 deficiency.
**How Zorevunersen Works Differently**
Zorevunersen is an **antisense oligonucleotide (ASO)** — a small synthetic molecule that works by targeting the genetic machinery itself. Rather than simply dampening overactive neurons, it instructs cells to produce more NaV1.1 protein from the healthy copy of the SCN1A gene that still exists in most patients.
Most people with Dravet syndrome have one mutated copy of SCN1A and one healthy copy. The healthy copy is there — it is simply not producing enough protein to compensate for the faulty one. Zorevunersen essentially turns up the volume on the healthy gene, increasing NaV1.1 production and restoring a closer approximation of normal neurological function.
This approach — **upregulation therapy** — is conceptually different from anything previously tried in epilepsy. It is less a drug than a genetic instruction.
**The Trial Results**
The Phase 1/2a trial enrolled **81 children aged 2 to 18** in the UK and the United States, making it one of the largest early-phase trials ever conducted for Dravet syndrome. The trial was led by teams at UCL Great Ormond Street Institute of Child Health in London and Lurie Children's Hospital / Northwestern University in Chicago.
Key findings:
- Children receiving **70mg zorevunersen** experienced seizure reductions ranging from **59% to 91%** over 20 months of the extension study - Some patients saw **motor seizure reductions of approximately 85% at three months** and **73% at six months** following their 70mg dose - The drug was **safe and well-tolerated** — no serious unexpected adverse events were recorded - Improvements were seen not just in seizure frequency but in **cognition and behaviour**, suggesting effects beyond seizure suppression alone - Effects were **durable** — the reductions held across the extended follow-up period, not just in early months
Zorevunersen has received **FDA Breakthrough Therapy Designation**, a status reserved for drugs that show preliminary clinical evidence of substantial improvement over existing treatments for serious conditions. The designation is designed to accelerate development and regulatory review.
**The Phase 3 Trial**
A global Phase 3 trial — the **EMPEROR study** — is currently underway, enrolling approximately 150 patients aged 2 to under 18 with confirmed SCN1A gene variants. The trial is randomised, double-blind, and sham-controlled, with its primary endpoint focused on reductions in major motor seizure frequency.
If EMPEROR confirms what Phase 1/2a showed, zorevunersen will move toward regulatory approval — potentially becoming the first disease-modifying treatment for Dravet syndrome ever approved.
**What This Means for Families**
Dr. Helen Cross, the 'Prince of Wales Chair in Childhood Epilepsy' at UCL's Great Ormond Street Institute of Child Health and a lead investigator on the trial, said: *'These results are very encouraging. For the first time, we have clinical evidence that an ASO drug targeting the underlying genetic cause of Dravet syndrome can meaningfully reduce seizures and improve children's quality of life over an extended period.'*
For the families who participated in the trial — many of whom had watched their children go through years of medication trials, hospital admissions, and seizures that conventional treatments couldn't stop — the results represent something they had almost stopped hoping for.
A drug that goes to the source. That tells the right gene to work harder. That gives the neurons what they were born without enough of.
The children in this trial did not stop having seizures entirely. But for many of them, the seizures became manageable in ways they had never been before. And a Phase 3 trial with 150 patients is the next step toward finding out whether that can become the standard of care for every child with Dravet syndrome worldwide. 🧬
*Sources: UCL News (ucl.ac.uk, March 2026) · The Guardian (March 4, 2026) · Stoke Therapeutics · Biogen · Dravet Syndrome Foundation · Epilepsy Society UK · ScienceDaily (March 4, 2026) · Northwestern University Feinberg School of Medicine (March 11, 2026)*
