Encoded Therapeutics to Present Interim Phase 1/2 Clinical Data on ETX101, the First One-time Gene Therapy in Development for Dravet Syndrome, at the 2025 American Epilepsy Society Annual Meeting

– Oral and poster presentations to include seizure and neurodevelopmental data from POLARIS Phase 1/2 Program that support advancement of ETX101 –

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)--Encoded Therapeutics Inc., a clinical-stage genetic medicines company, today announced upcoming presentations of interim clinical data from its ongoing POLARIS Phase 1/2 open-label trials evaluating ETX101 in children with SCN1A+ Dravet syndrome. The data will be featured at the American Epilepsy Society Annual Meeting, taking place December 5–9, 2025, in Atlanta, Georgia.

Dravet syndrome is a severe developmental and epileptic encephalopathy with onset in infancy, followed by a devastating period of escalating, treatment-resistant seizures and neurodevelopmental stagnation despite current medications. ETX101, an AAV9-based gene regulation therapy, was designed to target the root cause of Dravet syndrome by durably restoring SCN1A expression. The presentations will highlight interim safety data and early efficacy data from a single administration of ETX101, including seizure frequency through a 7-month observation period and outcomes on standardized neurodevelopmental assessments – the caregiver interview-based Vineland Adaptive Behavior Scales (VABS-3) and the clinician-administered Bayley Scales of Infant and Toddler Development (Bayley-4).

Presentation Details

“POLARIS Phase 1/2 Program Interim Safety and Preliminary Efficacy Results of ETX101, a One-Time Gene Regulation Therapy, in Young Children with Dravet Syndrome” will be presented by Joseph Sullivan, M.D., University of California, San Francisco, Principal Investigator on the ENDEAVOR study.

Oral Session: Platform session B.02
Date & Time: Friday, December 5, 2025, 12:45–1:00 pm ET
Location: Georgia World Congress Center Room B313

Poster Session: Poster #1.308
Date & Time: Saturday, December 6, 2025, 12:00–6:00 pm ET (Poster displayed); 12:00–2:00 pm ET (Author present)
Location: Georgia World Congress Center Exhibit Hall B2

About Dravet Syndrome

Dravet syndrome is a severe, lifelong developmental and epileptic encephalopathy (DEE) that begins in infancy. Most cases are caused by variants in the SCN1A gene, resulting in reduced Na_V1.1 protein in the brain. Seizures typically begin within the first year of life and are frequent, prolonged, and difficult to control, even with treatment. As the disease progresses, people experience cognitive and developmental delays, motor and balance difficulties, sleep disturbances, and behavioral challenges. Dravet syndrome carries a high risk of SUDEP (Sudden Unexpected Death in Epilepsy), with up to 1 in 5 children dying before adulthood. Dravet syndrome affects approximately 35,000 people in the United States, United Kingdom, EU4 and Japan. Currently, there are no approved disease-modifying therapies for Dravet syndrome, leaving a significant and urgent unmet need for patients and families. More information about Dravet syndrome can be found at www.dravetfoundation.org.

About ETX101

ETX101 is an AAV9-based gene regulation therapy in development to treat SCN1A+ Dravet syndrome. ETX101 is designed to target the underlying cause of Dravet syndrome by increasing SCN1A expression in GABAergic inhibitory neurons with a single administration. By addressing this root mechanism, ETX101 has the potential to treat the full spectrum of Dravet symptoms, including seizures, communication and cognitive impairment, behavioral issues, and motor dysfunction. ETX101 has received Regenerative Medicine Advanced Therapy, Fast Track, Rare Pediatric, and Orphan Drug Designations from the U.S. Food and Drug Administration, as well as Orphan Designation from the European Medicines Agency.

About the POLARIS Studies: ENDEAVOR (United States), EXPEDITION (United Kingdom), and WAYFINDER (Australia)

The POLARIS program is a comprehensive clinical investigation of ETX101 in infants and young children (6 months to <7 years of age) with SCN1A+ Dravet syndrome, comprising multiple clinical trials. The first phase of POLARIS comprises three Phase 1/2 open-label, dose-escalation, multi-center trials. The primary objective of the studies is to assess the safety and tolerability of ETX101. Secondary objectives are to evaluate the gene therapy's efficacy by assessing the percent change from baseline in monthly countable seizure frequency (MCSF), as well as the impact on the neurodevelopmental symptoms of Dravet syndrome, including cognition, communication, and motor function.

About Encoded Therapeutics

Encoded Therapeutics is a clinical-stage genetic medicines company developing one-time therapies for severe neurological disorders. Our vector engineering platform enables highly selective, potent, and durable gene modulation. The lead program, ETX101, is designed to address the underlying cause of Dravet syndrome by durably upregulating SCN1A and is currently in Phase 1/2 clinical trials. Building on this foundation, we are advancing programs to selectively modulate validated genetic targets in chronic pain, Angelman syndrome, and Alzheimer’s disease/tauopathies. With integrated discovery, development, and manufacturing capabilities, we are positioned to efficiently move programs from concept through the clinic. We are driven by a mission to pioneer transformative therapies that meaningfully improve the lives of patients and families affected by devastating neurological conditions. For more information, please visit www.encoded.com.