We are developing purpose-built genetic medicines by utilizing a biology-first approach paired with optimized delivery.

Gene therapy isn’t “plug-and-play.” Each disease requires a therapy engineered to its biology—and delivered where it can work—so patients get the best chance at meaningful benefit when there might be only one shot to get this right.

Our programs start with the underlying biology of disease—from gene selection and construct design to expression control—and pair it with fit‑for‑purpose delivery to reach the right cells. We run on a safety‑by‑design mindset, integrating preclinical learnings, clinical monitoring, and manufacturing quality and controls to balance efficacy with safety throughout development.

Biology-first Design

Purposefully built constructs aligned to disease biology; expression control tuned for the cellular target.

Precision Delivery

Route, dose and biodistribution strategies optimized to reach relevant neural systems and sustain benefit.

Safety by Design

Guardrails across CMC, clinical monitoring and risk mitigation to design for safer outcomes.

We are advancing a gene therapy pipeline to help address the high unmet needs of patients with rare neurological diseases, with a focus on Rett syndrome.

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NGN-401 for Rett Syndrome Pipeline Chart
  • Embolden™ Registrational Trial Ongoing

About Rett Syndrome

Rett syndrome prevalence graphicRett syndrome is a rare, progressive genetic neurodevelopmental disorder caused by variants in the MECP2 gene on the X chromosome. The variants lead to deficiency of the MeCP2 protein, which is responsible for normal function in the brain and other parts of the nervous system.

Children with Rett syndrome typically experience developmental delay at 6-18 months, then lose previously acquired skills—including speech, purposeful hand use and gross and fine motor abilities. Hallmark features include:

  • Loss of expressive and receptive communication
  • Loss of purposeful hand function and repetitive hand movements
  • Gait abnormalities and mobility challenges
  • Seizures, breathing irregularities and severe constipation

Rett syndrome has an estimated global incidence of 1 in 10,000 females1 and is estimated to affect approximately 15,000 females2 in the US, EU and UK.

1 Laurvick CL, de Klerk N, Bower C, Christodoulou J, Ravine D, Ellaway C, Williamson S, Leonard H. Rett syndrome in Australia: a review of the epidemiology. J Pediatr. 2006 Mar;148(3):34752. doi: 10.1016/j.jpeds.2005.10.037. PMID: 16615965

2 Based on incidence rates of 1:10,000 female births, Orphanet. (2021, January). Rett syndrome (ORPHA:778).

About NGN-401

NGN-401 is an investigational AAV9 gene therapy being developed as a one-time treatment for Rett syndrome. It is the first clinical candidate to deliver the full-length human MECP2 gene under the control of Neurogene’s EXACT™ transgene regulation technology. EXACT technology is an important advancement in gene therapy for Rett syndrome, specifically because the disorder requires a treatment approach that enables targeted levels of MECP2 transgene expression without causing overexpression-related toxic effects associated with conventional gene therapy.

Requirements for one-time gene therapy for Rett Syndrome
Requirements for one-time gene therapy for Rett Syndrome

Rett Syndrome Clinical Program

Embolden LogoWe are evaluating NGN-401 in Embolden™, our open-label, baseline-controlled registrational clinical trial evaluating a single dose of NGN-401 (1E15 vg) in females with Rett syndrome ages three and older. The primary endpoint of Embolden is a Clinical Global Impression-Improvement (CGI-I) scale score of ≤3 and a new developmental milestone/skill documented on video and independently verified by blinded central raters.

Embolden was converted from our Phase 1/2 clinical trial evaluating NGN-401. Data from the Phase 1/2 trial have shown that participants who received NGN-401 experienced multidomain, durable gains with continued skill acquisition over time. In an interim update from the pediatric cohort (ages 4-10 cohort; n=10 for safety, n=8 for efficacy) of the trial with a data cutoff date of October 30, 2025:

  • Participants showed functional improvements, including developmental milestones/skills gained across core clinical domains of Rett syndrome – hand function/fine motor, language/communication and ambulation/gross motor
  • For participants who achieved improvements in the Clinical Global Impression-Improvement (CGI-I), those gains were durable as of the November 2024 interim data report
  • NGN-401 at the 1E15 vg dose was generally well-tolerated in the pediatric cohort and the adolescent/adult cohort (ages ≥ 11 cohort)

NGN-401 Regulatory Designations

NGN-401 was selected by the U.S. Food and Drug Administration (FDA) for its START Pilot Program and has also received Regenerative Medicine Advance Therapy (RMAT) designation, orphan drug designation, Fast Track designation and rare pediatric designation from the FDA. Neurogene was previously granted an INTERACT meeting with the FDA regarding the EXACT technology. NGN-401 also received Priority Medicines (PRIME) designation, orphan designation and advanced therapy medicinal product designation from the European Medicines Agency (EMA) and the Innovative Licensing and Application Pathway (ILAP) designation from the United Kingdom (UK) Medicines and Healthcare products Regulatory Agency (MHRA).

Other Programs

About NGN-101

NGN-101 is our development candidate for the treatment of CLN5 Batten disease. NGN-101 contains conventional gene therapy elements designed to deliver the CLN5 gene and is packaged in an AAV9 capsid. We have completed enrollment in CLN5-200, our Phase 1/2 clinical trial evaluating NGN-101, and we are continuing to follow participants in the trial. For more information about our CLN5 Batten disease program, including CLN5-200, reach us at [email protected].

Expanded Access Policy

Neurogene is focused on developing life-changing genetic medicines for patients and their families affected by rare, devastating neurological diseases. To accomplish this, we collaborate with many researchers, the patient community, patient advocacy organizations, and physicians, in addition to working closely with global regulatory agencies. With the development of medicines that will be safe, effective, and satisfy unmet medical need, comes the promise that these medicines will be broadly accessible to appropriate patients in the future.

Our Policy

Currently, Neurogene does not offer an expanded access program.

Neurogene carefully considered our policy on providing access to investigational gene therapies outside of a clinical trial. We took into account multiple considerations, including patient safety, potential risks and benefits, the impact to the broader patient population, resourcing, and other ethical considerations. At this time in development, availability and access to Neurogene investigational therapies is possible only through participation in clinical trials. Clinical trials are carefully regulated, monitored, and conducted in specific patient populations to assess safety, and serve a critical role in understanding the risks and potential benefits of investigational therapeutic options, such as gene therapy. For these reasons, we believe that completing the necessary clinical trials and obtaining the data needed for review and approval by regulatory agencies is the fastest and most scientifically sound way toward making Neurogene’s gene therapies available to the broader patient population.

If you are a patient or family member and have questions about this policy, please contact [email protected]. You can also learn more about our current investigational gene therapy programs and access resources for patients and families.

If you are a healthcare provider and have questions about this policy, please contact [email protected].

What is Rett Syndrome?What is Rett Syndrome?

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