Gene therapy for females with Rett syndrome

A Baseline-Controlled, Open-Label, Multicenter, Single-Arm, Pivotal Study to Evaluate the Efficacy, Safety, and Tolerability of NGN-401 in Subjects With Rett Syndrome (Embolden)

Phase 3 Interventional Neurogene Inc. · NCT05898620

This study is testing a new gene therapy to see if it can help girls with Rett syndrome by delivering a missing gene to their brains.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment33 (estimated)
Ages3 Years and up
SexFemale
SponsorNeurogene Inc. Industry-sponsored
Locations16 sites (Birmingham, Alabama and 15 other locations)
Trial IDNCT05898620 on ClinicalTrials.gov

What this trial studies

This study evaluates the safety and efficacy of NGN-401, a novel gene therapy, in females diagnosed with typical Rett syndrome. It is a phase 1/2, open-label study that utilizes an adeno-associated viral vector serotype 9 (AAV9) to deliver a full-length human MECP2 gene, aiming to express therapeutic levels of the MECP2 protein. Participants will receive a single administration of the treatment under general anesthesia via intracerebroventricular delivery and will be monitored for safety and preliminary efficacy for five years, with an option for long-term follow-up for an additional ten years.

Who should consider this trial

Good fit: Ideal candidates are females diagnosed with typical Rett syndrome who have a documented mutation in the MECP2 gene.

Not a fit: Patients with normal or near-normal hand function or those with significant comorbid conditions may not benefit from this study.

Why it matters

Potential benefit: If successful, this therapy could significantly improve the quality of life and functional outcomes for patients with Rett syndrome.

How similar studies have performed: While gene therapy approaches for genetic disorders are being explored, this specific application for Rett syndrome is novel and has not been extensively tested in prior studies.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Females who are between the ages of ≥4 and ≤10 years for Arms 1 and 2 (Arms closed). Females who are ≥11 years of age or older for Arm 3 (Arm closed). Females who are ≥3 for Arm 4, the pivotal cohort.
* Diagnosis of typical Rett syndrome with a documented disease-causing mutation in the methyl-CpG-binding protein 2 (MECP2) gene
* Current anti-epileptic drug regimen has been stable for at least 12 weeks
* Participant must be in the post-regression stage
* Participant and caregiver should reside within a 2-hour drive of the study center for at least 3 months following treatment
* Participant must have never taken trofinetide or have taken trofinetide and discontinued due to tolerability, lack of efficacy, or other reasons. Following NGN-401 dosing, trofinetide may be initiated after a specified time period and with the support of the treating clinician.

Exclusion Criteria:

* Normal or near normal hand function
* Has a current clinically significant condition other than Rett syndrome
* Presence of a concomitant medical condition that precludes intracerebroventricular administration, or use of anesthetics or immune suppression needed for study related procedures

Other inclusion and exclusion criteria apply.

Where this trial is running

Birmingham, Alabama and 15 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Rett SyndromeTypical Rett SyndromeMECP2Rett DisorderGenetic Diseases, InbornGenetic Diseases, X-LinkedNeurodevelopmental DisordersNeurobehavioral Manifestations
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.