Neurogene's Rett Syndrome Gene Therapy Trial Paused After Serious Adverse Event
Key Insights
Neurogene's stock plummeted after disclosing a serious adverse event in a patient receiving a high dose of NGN-401, its gene therapy for Rett syndrome (search).
The adverse event, occurring in the third patient dosed at the higher level, is consistent with known risks associated with AAV gene therapies.
Preliminary data from the low-dose cohort showed promising efficacy, with all four patients achieving 'much improved' ratings and reaching developmental milestones.
Neurogene experienced a significant setback in its clinical trial for NGN-401, a gene therapy targeting Rett syndrome (search), after a participant experienced a serious adverse event. The event, which occurred in the third patient receiving a higher dose of the therapy, led to a sharp decline in the company's stock price. This news comes shortly after Neurogene successfully raised $200 million through a private investment.
Clinical Trial Details and Initial Efficacy
NGN-401 is designed to deliver a functional copy of the MECP2 (search) gene, which is mutated in individuals with Rett syndrome (search). The initial data from the low-dose cohort of the trial showed promising results. All four patients, aged between 4 and 7 years, achieved a "much improved" rating on a clinician assessment used to evaluate changes in condition. Furthermore, these patients acquired new skills or reached developmental milestones in areas typically affected by Rett syndrome.
Across the low-dose cohort, as well as two patients on the high dose, there were no treatment-related serious adverse events or seizures reported following NGN-401 infusion. Most other side effects were responsive to steroid treatment and were either resolved or resolving. The serious adverse event occurred in the third patient who received the high dose of NGN-401.
Safety Concerns and AAV Gene Therapy Risks
Neurogene stated that the adverse event was "consistent with known risks" associated with gene therapies that utilize adeno-associated virus (AAV) vectors to deliver the therapeutic gene. AAV gene therapies have been previously linked to liver and heart toxicity, as well as severe immune reactions in some instances. The company has not provided further details on the specific nature of the adverse event.
Analyst Perspectives
Despite the adverse event, some analysts remain optimistic about the potential of NGN-401. Paul Matteis, an analyst at Stifel, noted that the preliminary data showed a "real clinical benefit" across the four pediatric Rett patients in the low-dose cohort. However, Christopher Raymond, an analyst at Piper Sandler, suggested that Neurogene might focus on the low dose moving forward, given the safety concerns associated with the high dose.
Implications for Rett Syndrome Treatment Landscape
The setback for Neurogene could potentially benefit Taysha Gene Therapies, which is also developing a gene therapy for Rett syndrome (search). Taysha's stock price increased following the announcement of Neurogene's adverse event. The Rett syndrome treatment landscape remains an area of unmet medical need, and the development of effective gene therapies could offer significant improvements for patients with this neurodevelopmental disorder.
Batten Disease Program Discontinuation
In addition to the challenges with the Rett syndrome (search) program, Neurogene also announced its decision to discontinue development of its gene therapy for Batten disease (search). This decision follows the FDA's denial of the company's request for a special designation designed to streamline regulatory interactions and assessments.