First treatment targeting the genetic root of Dravet syndrome shows dramatic seizure reduction

Overview

Updated May 30

Dravet syndrome is a severe genetic epilepsy that causes hundreds of seizures per month, cognitive decline, and a 15–20 percent mortality rate. For nearly five decades, no treatment addressed the underlying cause — including two drugs approved in the past eight years, which could only partially suppress symptoms.

On March 5, 2026, the New England Journal of Medicine published the first clinical evidence that a drug can modify Dravet syndrome itself. The drug, zorevunersen, is an antisense oligonucleotide that boosts protein production from the healthy copy of the gene responsible for the condition. In 81 children, it reduced motor seizures by up to 91 percent and sustained improvements in cognition and behavior over three years.

Zorevunersen also points beyond Dravet syndrome, which affects roughly 1 in 16,000 children — the approach could treat hundreds of conditions caused by loss-of-function mutations in a single gene. A Phase 3 trial of approximately 150 patients is expected to finish enrollment by mid-2026, with results anticipated in mid-2027 that could support a Food and Drug Administration (FDA) submission. If approved, zorevunersen would be the first disease-modifying treatment for any genetic epilepsy.

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Key Indicators

91%

Maximum seizure reduction

Median reduction in convulsive seizure frequency observed in the highest-dose cohort during the open-label extension studies.

Patients treated

Children and adolescents ages 2 to 18 who received at least one dose of zorevunersen across Phase 1/2a studies.

3 years

Sustained benefit duration

Duration over which improvements in seizures, cognition, and behavior were maintained in extension studies.

~150

Phase 3 enrollment target

Number of patients in the EMPEROR registrational trial, with enrollment expected to complete in Q2 2026.

1 in 15,700

Incidence rate

Estimated incidence of Dravet syndrome per live births in the United States—more than twice earlier estimates.

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People Involved

Adrian Krainer

Co-founder, Stoke Therapeutics; Professor, Cold Spring Harbor Laboratory

Co-founder of Stoke Therapeutics and scientific architect of the TANGO platform

Isabel Aznarez

Co-founder, Stoke Therapeutics

Co-founder of Stoke Therapeutics and co-inventor of the TANGO platform

Charlotte Dravet

French epileptologist who first described the syndrome

Retired; the condition bears her name

Organizations Involved

Stoke Therapeutics

Biotechnology Company

Developer of zorevunersen; leading the Phase 3 EMPEROR trial

A publicly traded biotechnology company developing antisense oligonucleotide therapies for genetic diseases caused by insufficient protein production.

Biogen

Pharmaceutical company

Co-developer with rights to zorevunersen outside North America

A major neuroscience-focused pharmaceutical company that previously brought the first antisense oligonucleotide therapy for a neurodegenerative disease (Spinraza for spinal muscular atrophy) to market.

U.S. Food and Drug Administration

Federal regulatory agency

Granted Breakthrough Therapy Designation to zorevunersen

The U.S. agency responsible for approving new drugs; its Breakthrough Therapy Designation allows accelerated development for drugs treating serious conditions.

Timeline

January 1978 March 2026

13 events Latest: March 5th, 2026 · 6 months ago Showing 8 of 13

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March 2026
NEJM publishes first disease-modifying evidence for Dravet syndrome
Latest Scientific

The New England Journal of Medicine publishes results from Phase 1/2a and open-label extension studies showing zorevunersen reduced seizures by up to 91 percent in 81 children, with sustained cognitive and behavioral improvements over three years—the first evidence of disease modification in any genetic epilepsy.
March 5th, 2026
January 2026
Phase 3 EMPEROR trial on track, enrollment nearing completion
Clinical

Stoke announces that approximately 60 patients have been randomized and dosed in the Phase 3 EMPEROR trial, with enrollment of 150 patients expected to complete in Q2 2026 and data readout targeted for mid-2027.
January 11th, 2026
December 2025
Three-year data presented at American Epilepsy Society meeting
Scientific

Presentations at the American Epilepsy Society annual meeting show durable improvements in seizures, cognition, and behavior through 36 months of treatment across open-label extension studies.
December 5th, 2025
September 2025
Data at International Epilepsy Congress support disease modification
Scientific

Stoke and Biogen present data at the 36th International Epilepsy Congress showing sustained seizure reduction and cognitive improvements that support zorevunersen's disease-modifying potential.
September 2nd, 2025
February 2025
Biogen pays $165 million to partner on zorevunersen
Corporate

Biogen enters a collaboration with Stoke Therapeutics worth up to $550 million for rights to zorevunersen outside North America, covering 30 percent of development costs.
February 18th, 2025
January 2024
FDA grants Breakthrough Therapy Designation to zorevunersen
Regulatory

The FDA designates zorevunersen a Breakthrough Therapy for Dravet syndrome, signaling substantial improvement over existing treatments and enabling accelerated development pathways.
January 1st, 2024
June 2020
FDA approves fenfluramine as second Dravet treatment
Regulatory

Fintepla (fenfluramine) becomes the second FDA-approved treatment for Dravet syndrome seizures, still focused on symptom management rather than the disease mechanism.
June 25th, 2020
April 2020
Charlotte Figi dies at age 13
Milestone

Charlotte Figi, whose story transformed medical cannabis policy in the United States and gave hope to Dravet families, dies of complications from pneumonia at age 13.
April 7th, 2020
June 2018
FDA approves Epidiolex, first cannabidiol drug for Dravet
Regulatory

The FDA approves Epidiolex (cannabidiol) as the first prescription CBD treatment for Dravet syndrome seizures, managing symptoms but not addressing the underlying genetic cause.
June 25th, 2018
January 2018
Stoke Therapeutics founded to target Dravet's root cause
Corporate

Adrian Krainer and Isabel Aznarez launch Stoke Therapeutics with $40 million in funding to develop antisense oligonucleotide therapies using their TANGO platform, beginning with Dravet syndrome.
January 4th, 2018
January 2012
Charlotte Figi's story popularizes CBD treatment for Dravet
Milestone

Five-year-old Charlotte Figi, experiencing 300 seizures per week, begins taking a low-THC cannabis extract that reduces her seizures dramatically. Her story sparks a national conversation about medical cannabis.
January 1st, 2012
January 2001
SCN1A gene identified as the cause of most Dravet cases
Discovery

Researchers discover that mutations in the SCN1A gene, which encodes a sodium channel protein critical for brain function, cause over 90 percent of Dravet syndrome cases.
January 1st, 2001
January 1978
Charlotte Dravet describes a new epilepsy syndrome in infants
Discovery

French epileptologist Charlotte Dravet documents a pattern of severe seizures beginning in the first year of life that resists standard treatments, initially called severe myoclonic epilepsy of infancy.
January 1st, 1978

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Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

2012-2018

Charlotte Figi and the medical cannabis movement for epilepsy (2012-2018)

Charlotte Figi, a five-year-old with Dravet syndrome experiencing up to 300 seizures per week, began taking a low-THC cannabis extract in 2012 that reduced her seizures to two or three per month. Her story, featured in a 2013 CNN documentary by Sanjay Gupta, transformed the national debate on medical cannabis and led directly to the FDA's 2018 approval of Epidiolex, the first prescription cannabidiol drug.

Then

Charlotte's story catalyzed medical cannabis legalization across dozens of U.S. states and gave the Dravet community its first moments of public visibility. Epidiolex showed 43 percent of patients achieving a greater than 50 percent seizure reduction.

Now

While Epidiolex and fenfluramine improved seizure management, neither addressed the underlying genetic cause. Charlotte Figi died in 2020 at age 13. The gap between symptom management and disease modification underscored the need for therapies like zorevunersen that target the root mechanism.

Why this matters now

The Dravet community's experience with CBD illustrates both the desperation that drives families toward any available treatment and the limits of symptom management. Zorevunersen's disease-modifying data represent a fundamentally different approach—not suppressing seizures after they start, but addressing the protein deficiency that causes them.

December 2016

Spinraza for spinal muscular atrophy (2016)

Biogen and Ionis Pharmaceuticals won FDA approval for nusinersen (Spinraza), an antisense oligonucleotide delivered via intrathecal injection to treat spinal muscular atrophy (SMA), a genetic disease that destroys motor neurons in infants and children. In the pivotal ENDEAR trial, 51 percent of treated infants achieved motor milestones versus zero percent in the control group, with a 47 percent reduction in the risk of death or permanent ventilation.

Then

Spinraza became the first approved treatment for SMA and demonstrated that antisense oligonucleotides delivered to the central nervous system could modify a genetic disease. It generated over $2 billion in annual revenue at peak.

Now

Spinraza validated the entire class of intrathecally delivered antisense oligonucleotides for neurological genetic diseases and proved that boosting protein production from a related gene could compensate for a defective one—the same principle underlying zorevunersen.

Why this matters now

Zorevunersen uses the same drug class (antisense oligonucleotide), the same delivery method (intrathecal injection), and involves the same commercial partner (Biogen) as Spinraza. Adrian Krainer, Stoke's co-founder, contributed to the RNA splicing research that enabled Spinraza. The Dravet program is essentially applying lessons from the SMA success to a different genetic disease.

2018

Inotersen and tafamidis for hereditary transthyretin amyloidosis (2018)

In 2018, the FDA approved two drugs targeting the same rare genetic disease through different mechanisms: inotersen (an antisense oligonucleotide that reduces production of a misfolded protein) and tafamidis (a small molecule that stabilizes the protein). Both demonstrated disease modification in hereditary transthyretin amyloidosis, a condition where a single gene mutation causes toxic protein buildup that damages the heart and nerves.

Then

Both approvals validated the principle that targeting a disease's genetic mechanism—rather than its downstream symptoms—could produce durable clinical benefit in rare genetic conditions.

Now

The transthyretin amyloidosis approvals helped establish the regulatory and commercial framework for precision genetic medicines, demonstrating that rare disease drugs targeting root causes could command premium pricing and achieve meaningful market adoption despite small patient populations.

Why this matters now

Like zorevunersen, these drugs showed that modifying gene expression or protein function in a rare genetic disease could yield durable, disease-modifying results. They established the regulatory precedent and commercial viability that companies like Stoke are now building on.