Neurogene Inc. (NASDAQ:NGNE) experienced a strong after-hours rally of about 30% on Thursday after the company disclosed that the U.S. Food and Drug Administration had granted Breakthrough Therapy designation to NGN-401, its investigational gene therapy aimed at treating Rett syndrome.
The FDA decision was grounded in interim efficacy and safety findings from Neurogene's Phase 1/2 trial as of October 30, 2025. According to the company, those data demonstrated clinically meaningful and durable functional improvements across multiple domains of Rett syndrome, with patients showing continued acquisition of skills over time.
NGN-401 is engineered as a single-administration treatment that delivers the full-length human MECP2 gene. Neurogene is using its EXACT transgene regulation platform to control expression of the transgene. The therapy is administered via intracerebroventricular delivery, a route designed to target the brain and nervous system directly.
Neurogene is currently conducting the Embolden registrational clinical trial for NGN-401. The company expects to complete dosing in that trial in the second quarter of 2026, and it has signaled plans to present additional interim Phase 1/2 clinical data in mid-2026.
Regulatory context and potential advantages
Breakthrough Therapy designation is intended to accelerate the development and review of medicines for serious conditions when preliminary clinical evidence indicates a substantial improvement over available therapies. The designation can confer multiple regulatory advantages, including eligibility for Priority Review, the ability to submit portions of the Biologics License Application on a rolling basis, and enhanced organizational engagement from the FDA to identify an efficient path to approval.
NGN-401 had already received several prior FDA regulatory designations. The therapy was previously granted Regenerative Medicine Advanced Therapy and Rare Pediatric Disease designations, and it was chosen for the FDA's Support for Clinical Trials Advancing Rare Disease Therapeutics Pilot Program.
Outlook and near-term milestones
Key near-term milestones cited by the company include completion of dosing in the Embolden registrational trial in the second quarter of 2026 and the presentation of further interim Phase 1/2 data in mid-2026. These upcoming steps will provide additional clinical information that underpinned the FDA's Breakthrough Therapy decision.