SOUTH SAN FRANCISCO, Calif. — Encoded Therapeutics said it has aligned with the U.S. Food and Drug Administration on the design of a pivotal study for its investigational gene therapy ETX101, marking a key step toward a planned regulatory submission for the treatment of Dravet syndrome.
The company said it has initiated a 30-patient pivotal trial evaluating the therapy in infants and young children ages 6 months to under 4 years, with a focus on reducing seizure frequency and improving neurodevelopmental outcomes.
“Our alignment with the FDA on the pivotal study design marks an important step toward regulatory approval of ETX101 for children with Dravet syndrome,” said Sal Rico, M.D., Ph.D., Chief Medical Officer of Encoded. “This study design provides a rigorous and efficient path to evaluate ETX101 in the youngest population where we have the greatest opportunity to demonstrate a rapid and transformative benefit, while the ENDEAVOR Part 1B study enables the assessment of disease-modifying potential of ETX101 across the entire population of older children and adolescents with Dravet syndrome.”
The pivotal study, known as ENDEAVOR Part 2, will compare a single administration of ETX101 against a delayed-treatment control over 52 weeks. The primary endpoint is reduction in monthly seizure frequency, with additional measures assessing cognitive development and overall function.
Encoded is also expanding its earlier-stage ENDEAVOR Part 1 study to include older children and adolescents ages 4 to under 18, with an emphasis on safety, tolerability, and preliminary signs of effectiveness. The company expects patient dosing in both studies to begin in the second quarter of 2026.
The study design builds on positive interim data from the company’s POLARIS Phase 1/2 trial, which showed sustained seizure reductions and improvements in neurodevelopment among treated patients.
In parallel, Encoded said clinical data for ETX101 will be featured in a Presidential Symposium at the 2026 American Society of Gene & Cell Therapy Annual Meeting in Boston, highlighting the growing interest in the program.
ETX101 is an investigational gene regulation therapy designed to increase expression of the SCN1A gene, targeting the underlying cause of Dravet syndrome. The one-time treatment is delivered directly into the brain and is intended to provide long-term benefits across a range of symptoms, including seizures, cognitive impairment, and motor dysfunction.
