NEW YORK, NY – Neurogene Inc. (Nasdaq: NGNE), a clinical-stage company founded to bring life-changing genetic medicines to patients and families affected by rare neurological diseases, today announced updated, positive data from its Phase 1/2 clinical trial evaluating NGN-401 gene therapy for the treatment of females with Rett syndrome.
Across 10 participants, 47 total developmental milestones were gained (average of 4.7 per participant), with both pediatric and adolescent/adult participants demonstrating clinical response and continued, progressive improvements through 30 months of follow-up, with no plateau or loss of milestones observed.
“We are encouraged by the long-term Phase 1/2 data across a broad age range and wide spectrum of disease severity, which we believe demonstrate that NGN-401 is driving gain of durable and clinically meaningful developmental milestones, and continued improvements were observed through 30 months of follow-up,” said Rachel McMinn, Ph.D., Founder and Chief Executive Officer of Neurogene. “Importantly, the gains of developmental milestones are not isolated events – they build over time with participants acquiring multiple milestones across the core Rett syndrome functional domains of hand function, gross motor function and communication. This multidomain progression is not observed in the natural history of Rett syndrome, and we believe supports NGN-401’s differentiated profile, driven by its purposeful design and targeted delivery.”
“In typical development, children gain milestones in an organized, cumulative sequence, with each milestone building on the last; in Rett syndrome, that process is stopped by regression,” said Bernhard Suter, M.D., Medical Director of the Blue Bird Circle Rett Center at Texas Children’s Hospital, Associate Professor of Pediatrics and Neurology at Baylor College of Medicine, and principal investigator in the NGN-401 Phase 1/2 clinical trial. “These results show that the participants treated with NGN-401 are now gaining developmental milestones in a manner that suggests restarting developmental progression, something not observed in the natural history of the disease. As a result, participants are gaining greater independence and are more engaged in day-to-day activities with their families.”
Phase 1/2 Clinical Data as of Data Cutoff Date of June 16, 2026 (N=10, follow-up 12-30 months post-treatment)
Efficacy Data
- 100% of participants improved on the Clinical Global Impression-Improvement (CGI-I) scale and gained ≥1 developmental milestone, consistent with the composite endpoint used to evaluate efficacy in the EmboldenTM registrational trial
- 47 total developmental milestones were gained across participants, averaging 4.7 milestones per participant
- All participants gained ≥1 developmental milestone in the past 12 months
- Participants gained milestones in a progressive, developmentally ordered stepwise sequence, suggesting a restart of developmental progression
- Rapid onset of treatment effect, with median time to first clinical improvement of 2 months post-treatment
- Milestone gains deepened over time, increasing by 95% from 6 to 12 months and 147% from 6 to ≥12 months
- 7 of 10 participants gained ≥2 developmental milestones and demonstrated improvements across ≥2 core Rett syndrome domains; both of these improvements were observed in pediatric and adolescent/adult participants
- Continued improvement through 30 months post-dose, with no plateau observed and no milestones lost
- Participants experienced clinically meaningful improvements across additional validated Rett syndrome scales, including the Rett Syndrome Gross Motor Scale (RSGMS) and Rett Syndrome Hand Function Scale (RSHFS) (p<0.001)
Safety Data
- NGN-401 at the 1E15 vg dose remains generally well-tolerated
- All treatment-related adverse events have been mild (Grade 1) or moderate (Grade 2) in severity, and the majority are known potential risks of AAV and have resolved or are resolving
- No new treatment-related SAEs reported since last data cutoff date in October 2025
- NGN-401 continues to be generally well-tolerated in Embolden, with no treatment-related SAEs or DLTs as of the data cutoff date of June 16, 2026
Neurogene management and Dr. Suter will discuss these results during a live webcast today, June 29, 2026, at 8:00 a.m. ET. The live webcast presentation will be accessible from the Investor Relations section of the Company’s website under Events, where a replay of the event will also be available for a limited time.
These data, as well as a poster presentation on the Rett Syndrome Natural History Study analysis to assess treatment effect in the Embolden trial, will also be presented at the 2026 International Rett Syndrome Foundation (IRSF) Rett Syndrome Scientific Meeting taking place in Prior Lake, Minn., June 29 – July 1, 2026.
About Neurogene
Neurogene (NASDAQ: NGNE) is a clinical-stage biotechnology company focused on developing life-changing genetic medicines for people and their families impacted by devastating neurological diseases. The Company is using a biology-first approach paired with optimized delivery to develop purpose-built genetic medicines, including programs powered by its novel and proprietary EXACT™ transgene regulation technology. Neurogene is advancing its lead gene therapy program, NGN-401, as a potential best-in-class, one-time treatment for Rett syndrome. For more information, visit neurogene.com or follow on LinkedIn.
About NGN-401
NGN-401 is an investigational AAV9 gene therapy in late-stage clinical development as a potential best-in-class, one-time treatment for Rett syndrome. It is the only clinical candidate to deliver the full-length human MECP2 gene and includes Neurogene’s EXACT™ transgene regulation technology, which is designed to deliver consistent, tightly controlled MeCP2 protein expression on a cell-by-cell basis. NGN-401 is delivered through intracerebroventricular administration to achieve the broadest targeting directly to the brain and nervous system based on nonclinical biodistribution data. NGN-401 is being evaluated in the Embolden™ registrational clinical trial. Data from the Phase 1/2 trial (as of June 16, 2026) have shown that participants experienced multidomain, durable gains with continued developmental milestone acquisition observed over time, and NGN-401 at the 1E15 vg dose has been generally well-tolerated. NGN-401 has received Breakthrough Therapy, Regenerative Medicine Advanced Therapy, Fast Track, Orphan Drug and Rare Pediatric Disease designations and selection for the START Pilot Program from the U.S. Food and Drug Administration, Advanced Therapy Medicinal Product, Orphan and Priority Medicines designations from the European Medicines Agency and Innovative Licensing and Application Pathway designation from the United Kingdom Medicines and Healthcare products Regulatory Agency.
Contacts
Media:
Mike Devine
Executive Director, Corporate Communications
[email protected]
Investor:
Lina Li
Executive Director, Investor Relations
[email protected]