SOUTH SAN FRANCISCO, Calif. — Encoded Therapeutics, Inc. (“Encoded”), a clinical-stage biotechnology company developing precision genetic medicines for severe neurological disorders, today announced that the first patient has been dosed in the pivotal ENDEAVOR Part 2 study of ETX101 for Dravet syndrome, marking an important transition into late-stage clinical development for the program. Encoded has also initiated dosing in the ENDEAVOR Part 1B expansion study in patients aged 4 to 18 years, extending evaluation of ETX101 across a broader patient population.
In addition, ETX101 has been selected for the FDA’s Chemistry, Manufacturing, and Controls Development and Readiness Pilot (CDRP) Program, supporting alignment of manufacturing readiness with accelerated clinical development. The company also announced advancement of its pipeline, with the nomination of ETX301 as a development candidate for post-amputation neuroma pain and an Investigational New Drug (IND) application planned for 2027.
ETX101 in Dravet Syndrome
ETX101, which has received Breakthrough Therapy designation from the FDA, is advancing as a potential disease-modifying therapy for SCN1A+ Dravet syndrome, with dosing now underway in the pivotal ENDEAVOR Part 2 study. This milestone builds on encouraging data from earlier clinical experience.
ETX101 is an AAV9‑based, cell‑selective gene regulation therapy designed to durably restore SCN1A expression and directly target the underlying cause of the disease. Part of the POLARIS program, ENDEAVOR Part 2 is evaluating seizure and neurodevelopmental outcomes in 30 infants and young children aged 6 months to 4 years, with enrollment expected to be completed by the end of 2026 and initial data anticipated by the end of 2027. The study is being conducted across multiple centers of excellence in the US, UK, and Australia.
Encoded has also dosed the first patient in ENDEAVOR Part 1B, an open-label expansion study assessing safety and preliminary efficacy in older children and adolescents aged 4 to 18 years. This study is designed to extend the evaluation of ETX101 across a broader patient population. Initial data from Part 1B is expected in the fourth quarter of 2026.
“Promising open-label data from the initial Phase 1/2 studies generated significant interest from the Dravet community, and dosing the first patients at the University of California, San Francisco in the pivotal and expansion studies is an important step forward for families affected by this disease,” said Adam Numis, M.D., Associate Professor of Neurology and Pediatrics at UCSF, and Principal Investigator for the ENDEAVOR studies. “This therapy is designed to target SCN1A and address the underlying genetic cause of disease. Evaluating this approach across infants, children, and adolescents reflects our dedicated effort to understand its potential to meaningfully alter disease trajectory in the broader patient population.”
ETX101 Selected for FDA CDRP Program
ETX101 has been selected for the FDA’s CDRP Program, which is designed to ensure that Chemistry, Manufacturing, and Controls (CMC) development keeps pace with clinical progress, particularly for therapies addressing serious unmet need. Participation in this selective program facilitates deeper engagement with the FDA to support Encoded’s manufacturing strategy as the program advances.
ETX301 in Post-Amputation Neuroma Pain
Encoded has nominated ETX301, an investigational AAV9‑based vectorized microRNA (miRNA), as a development candidate for post-amputation neuroma pain, with an IND submission planned for 2027. ETX301 is designed to selectively and durably knock down SCN9A (NaV1.7), a key mediator of pain signaling. The therapy is designed to target dorsal root ganglia (DRG) nociceptive neurons, with the goal of achieving durable analgesia while limiting potential off-target effects.
Painful neuromas following limb amputation represent a well-defined, localized neuropathic pain condition driven by aberrant peripheral nerve signaling, with evidence of increased NaV1.7 expression in affected tissues. ETX301 will initially be evaluated in patients with lower limb amputations, a population with a high burden of chronic pain and substantial impact on function and quality of life. Post-amputation neuroma pain affects an estimated 100,000 patients in the US, with approximately 5,000 new cases annually.
Encoded’s preclinical studies support the therapeutic potential of this approach, including durable NaV1.7 knockdown in non-human primates and sustained analgesic effects in rodent models of neuropathic pain.
“By targeting a key mediator of pain signaling, ETX301 has the potential to address conditions associated with severe and persistent pain in a fundamentally new way,” said Stephanie Tagliatela, Chief Scientific Officer of Encoded. “With an IND planned for 2027, we’re advancing a program grounded in strong preclinical data and enabled by the same platform and translational framework as ETX101.”
About ETX101
ETX101 is an investigational AAV9-based gene regulation therapy designed to increase the expression of the SCN1A gene to restore sodium channel function in inhibitory interneurons. By targeting the root mechanism, ETX101 has the potential to treat the full spectrum of Dravet syndrome symptoms, including seizures, communication and cognitive impairment, behavioral issues, and motor dysfunction. The therapy is administered via a single intracerebroventricular (ICV) injection and is designed for long-term benefit. ETX101 has received Breakthrough Therapy, Regenerative Medicine Advanced Therapy, Fast Track, Rare Pediatric Disease, and Orphan Drug designations from the FDA, was selected for the FDA’s CMC Development and Readiness Pilot (CDRP) Program and received Orphan designation from the European Medicines Agency (EMA).
About ETX301
ETX301 is an investigational AAV9-based vectorized microRNA (miRNA) therapy designed to selectively and durably knock down SCN9A (NaV1.7), a key mediator of pain signaling, in nociceptors. The therapy is designed for administration via a single intrathecal (IT) injection and is intended to deliver long-term benefit. ETX301 is currently in development for the treatment of chronic neuropathic pain caused by lower limb post-amputation neuroma, with an Investigational New Drug (IND) application anticipated in 2027. This initial indication is supported by the localized and well-characterized biology of painful neuromas, including evidence of upregulated NaV1.7 expression in affected tissues. By targeting a key mediator of pain signaling, ETX301 has the potential to address severe, intractable chronic pain across multiple settings.
About Encoded Therapeutics
Encoded Therapeutics is a clinical-stage biotechnology company developing one-time precision genetic medicines for severe monogenic and common neurological disorders. The company’s vector engineering platform enables highly targeted and cell-type-selective control of gene expression in the brain and peripheral nervous system, allowing potent and precise modulation of disease-relevant genes to address underlying disease biology. Encoded’s end‑to‑end innovation engine—spanning discovery, development, and in‑house GMP manufacturing—creates a streamlined path to advance a diversified pipeline of one‑time treatments across a broad range of neurological conditions. Encoded is driven by a mission to meaningfully improve the lives of patients and families affected by devastating neurological disorders. For more information, please visit www.encoded.com.
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