A Phase 3 interventional study of NGN-401 in Rett Syndrome, sponsored by Neurogene Inc.. Active, not recruiting at 16 sites in 3 countries. Open to female participants aged 3 Years and older. Per ClinicalTrials.gov, last updated 2026-06-10.
Sponsored by Neurogene Inc. · Phase 3, Interventional, and Treatment
This study will evaluate the efficacy and safety profiles of the investigational gene therapy, NGN-401, in females with typical Rett syndrome.
The pivotal study, Embolden (TM), is a conversion of the phase 1/2 study and is an open-label, baseline-controlled, multicenter, single-arm study designed to assess the efficacy, safety, and tolerability of administration of NGN401, an adeno-associated viral vector serotype 9 (AAV9) using Neurogene's proprietary transgene regulation technology. NGN-401 contains a full-length human MECP2 gene and is designed to express therapeutic levels of the MeCP2 protein while avoiding overexpression.
The study treatment will be given as a single administration under general anesthesia via intracerebroventricular (ICV) delivery. Each participant will be followed for efficacy and safety for 3 years after treatment, and is expected to enroll in a long-term follow-up study for 12 years.
96 studies on the registry are indexed under Rett Syndrome; 19 are open to participants now.
This study's planned enrollment of 33 is close to the median of 30 across 64 interventional studies indexed under Rett Syndrome.
Browse Rett Syndrome studies →Neurogene Inc. is the lead sponsor of 6 studies on the registry; none are open to participants now.
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Exclusion Criteria:
Other inclusion and exclusion criteria apply.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Dose Level 1 for ages 4-10 years
Genetic: NGN-401
Dose Level 1 for ages 11 years \& above
Genetic: NGN-401
Dose Level 2 for ages 4-10 years (discontinued)
Genetic: NGN-401
Dose Level 1 for ages 3 and above
Genetic: NGN-401
NGN-401 is a non-replicating, recombinant AAV9 carrying a full length human MECP2 transgene.
Efficacy of NGN-401
Responders will be defined as participants who: * Attain a CGI-I score of ≤ 3 ("minimally improved"); * and gain any one developmental milestone/skill from a list of 28, as captured through standardized video recordings and independently verified by blinded central raters.
Time frame: 52 Weeks
Plan to share: No
Started Jun 2023 (actual). Primary completion is estimated for Dec 2029, 78 months after the start.
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This study is active, not recruiting, as verified in Jun 2026. You cannot join it, but the record below documents what was studied.
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Neurogene Inc.