Neurogene reports 30-month data for NGN-401 in Rett syndrome trial

Neurogene Inc. (Nasdaq: NGNE) announced on June 29, 2026 updated long-term data from its Phase 1/2 trial of NGN-401 gene therapy for Rett syndrome, based on a data cutoff of June 16, 2026. Across 10 participants, 47 total developmental milestones were gained, averaging 4.7 per participant, with both pediatric and adolescent/adult participants showing continued, progressive improvements through 30 months of follow-up and no plateau or loss of milestones observed.¹

All participants improved on the CGI-I scale and gained at least one developmental milestone, consistent with the composite endpoint used in the Embolden registrational trial, and all gained at least one milestone in the past 12 months.¹ Milestones were gained in a progressive, developmentally ordered stepwise sequence, with a median time to first clinical improvement of 2 months post-treatment, and milestone gains increased by 95% from 6 to 12 months and 147% from 6 to at least 12 months.¹ Seven of 10 participants gained at least 2 developmental milestones and showed improvement across at least 2 core Rett syndrome domains.¹ Participants also showed improvements on the Rett Syndrome Gross Motor Scale and Rett Syndrome Hand Function Scale, with p<0.001.¹

On safety, NGN-401 at the 1E15 vg dose remains generally well-tolerated, with all treatment-related adverse events mild or moderate in severity, and no new treatment-related serious adverse events since the prior data cutoff in October 2025.¹

Dosing is complete in the Embolden registrational trial, with no treatment-related serious adverse events or dose-limiting toxicities as of the June 16, 2026 cutoff, and topline data are anticipated in the second half of 2027.¹ NGN-401 is an investigational AAV9 gene therapy in late-stage development, the only clinical candidate delivering the full-length human MECP2 gene using Neurogene's EXACT transgene regulation technology.¹