NGN-401 - (Embolden)

June 8, 2026: Neurogene Inc. (NASDAQ: NGNE) announced it completed dosing in Embolden, its multi-center, single-arm, open-label, baseline-controlled registrational trial of NGN-401 (AAV9 gene therapy) for females with Rett syndrome ages 3+ at a one-time 1E15 vg dose. The study exceeded its initial enrollment target (20) by dosing 25 participants; the statistical analysis plan pre-specifies an intent-to-treat population of up to 24, and the additional participant is intended to supplement safety/durability data.

The primary endpoint is a composite of Clinical Global Impression–Improvement (CGI-I) score ≤3 plus a gain from baseline in any one pre-specified developmental milestone. The primary analysis to support a planned BLA is expected after the first 24 participants complete 12 months follow-up; topline data are anticipated in 2H 2027. The trial’s success threshold is a minimum 33% response rate (≥8/24).

As of June 7, 2026, NGN-401 at 1E15 vg (n=35 across Phase 1/2 and Embolden) has been generally well-tolerated with no cases of hemophagocytic lymphohistiocytosis (HLH). Updated interim Phase 1/2 safety/efficacy data (≥12 months follow-up for all 10 participants) are expected mid-2026.