Neurogene Announces Expansion & Plans for More Rapid Patient Enrollment of Rett Syndrome Gene Therapy Clinical Trial

Neurogene Inc. recently announced the expansion of its ongoing Phase 1/2 gene therapy clinical trial for NGN-401 for female pediatric patients with Rett syndrome and updates to enable more rapid enrollment in the trial.

 “We are excited to share that we have met our first 2024 program milestones, including dosing the third patient in the NGN-401 Phase 1/2 trial for Rett syndrome and expansion of the trial to include more patients in the current dosing cohort and the addition of a high dose cohort,” said Founder and Chief Executive Officer, Rachel McMinn, PhD. “Our clinical development strategy has been to build flexibility and optionality early in the program with two concurrent dose cohorts designed to generate a more complete data package, which we expect will inform future registration discussions with global health authorities. We expect that expansion of the clinical trial and the removal of staggered dosing in Cohort 1 will enable us to treat more patients in a shorter period of time. Based on this update, we expect to complete enrollment of Cohort 1 in the second half of 2024.”

The US Phase 1/2 clinical protocol for NGN-401 has been amended as follows:

• Cohort 1, which specifies a total dose of 1×10¹⁵total vector genomes delivered via intracerebroventricular (ICV) administration, was expanded from five patients to eight patients. The dosing stagger has been removed from Cohort 1, enabling the remaining patients to be dosed in parallel.
• Cohort 2, which specifies a total dose of 3×10¹⁵total vector genomes delivered via ICV administration, was added and is expected to include a total of eight patients.
• The first three patients in Cohort 2 will be dosed in a staggered manner, with first patient dosing expected in the second quarter of 2024; pending Data and Safety Monitoring Board review of the safety data for the first three patients, the protocol will allow parallel enrollment for the remaining patients in Cohort 2.
• In addition, the protocol includes a targeted immunosuppression regimen for Cohort 2, designed as a preventative measure to aid in avoiding potential adeno-associated virus (AAV)-related immune responses that have been observed with other AAV-based products in this dose range. The immunosuppression regimen includes the use of rituximab and sirolimus, along with a shortened course of corticosteroids. Cohort 1 immunosuppression remains unchanged with corticosteroids alone.

A similar protocol amendment was submitted to the UK regulatory authorities. These changes are consistent with the Company’s guidance issued in January 2024. Importantly, in comprehensive nonclinical studies, the EXACT transgene regulation technology embedded in NGN-401 was shown to mechanistically constrain MECP2 transgene expression levels, allowing for the potential to dose escalate and enhance biodistribution to the brain, without the commensurate increase in MECP2 transgene expression observed with conventional gene therapy. Both doses in the updated protocol are below the “no observed adverse effect” level established in rodent and nonhuman primate models.

A third patient was dosed in the trial early in the first quarter. NGN-401 has been generally well-tolerated and there have been no treatment-emergent or procedure-related serious adverse events, or signs of overexpression-related toxicity observed in any patient.

Neurogene remains on track to report interim clinical data from Cohort 1 in the fourth quarter of 2024 and additional data, including from Cohort 2, in the second half of 2025.

Neurogene’s novel and proprietary EXACT gene regulation platform technology is a self-contained transgene regulation platform that can be tuned to deliver a desired level of transgene expression within a narrow and therapeutically relevant range, with the goal of avoiding transgene-related toxicities associated with conventional gene therapy. EXACT is compatible with viral and non-viral delivery platforms.

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 technology. The EXACT technology utilized in NGN-401 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. The robust nonclinical data package for NGN-401 provides evidence of a potentially compelling efficacy and safety profile in Rett syndrome.

Neurogene’s mission is to treat devastating neurological diseases to improve the lives of patients and families impacted by these rare diseases. Neurogene is developing novel approaches and treatments to address the limitations of conventional gene therapy in central nervous system disorders. This includes selecting a delivery approach to maximize distribution to target tissues and by designing products to maximize potency and purity for an optimized efficacy and safety profile. The company’s novel and proprietary EXACT transgene regulation platform technology allows for the delivery of therapeutic levels while limiting transgene toxicity associated with conventional gene therapy. Neurogene has constructed a state-of-the-art gene therapy manufacturing facility in Houston, Texas. GMP production of NGN-401 was conducted in this facility and will support pivotal clinical development activities. For more information, visit www.neurogene.com.