Stoke Therapeutics is preparing to advance its investigational drug, zorevunersen, into Phase III clinical trials for Dravet syndrome after the U.S. Food and Drug Administration (FDA) released its clinical hold on the program. This decision follows positive efficacy data from the Phase I/IIa MONARCH trial (NCT04442295) and its open-label extension (OLE) SWALLOWTAIL trial (NCT04740476), which demonstrated a reduction in convulsive seizure frequency in children and adolescents with Dravet syndrome.
The company's stock price saw an increase of 5.6% following the announcement, closing at $14.23 on August 6 and opening at $15.02 on August 7, before returning to normal levels during the day.
Zorevunersen Mechanism and Clinical Data
Zorevunersen sodium functions as an SCN1A activator, targeting the underlying genetic cause of Dravet syndrome. The SCN1A gene is crucial for producing the Nav1.1 sodium channel, which plays a vital role in neuronal communication in the brain. By increasing the production of Scn1a messenger RNA and the Nav1.1 protein, zorevunersen aims to restore normal neuronal function without affecting other ion channels.
While the earlier trials showed promising efficacy, approximately one-third of patients experienced adverse events, including elevated CSF protein, vomiting, and irritability. Twenty-two percent of patients had serious adverse events, with only one case deemed related to the study drug.
Regulatory Path and Future Plans
Stoke Therapeutics plans to engage with the FDA and other global regulatory bodies in the latter half of 2024 to finalize a single, global Phase III registrational study design. "We thank the FDA for working with us to remove the partial clinical hold and look forward to continuing our discussions with them and with other global regulatory agencies toward the goal of agreeing on a single, global Phase III registrational study design by year-end," said Dr. Edward Kaye, Stoke Therapeutics' CEO.
Zorevunersen has already received orphan drug designation from both the FDA and the EMA, as well as rare pediatric disease designation from the FDA, underscoring the urgent need for effective treatments for this rare and severe condition.
Dravet Syndrome: Unmet Needs
Dravet syndrome is a severe, progressive genetic epilepsy characterized by frequent, prolonged, and treatment-resistant seizures that typically begin in the first year of life. Beyond seizures, the condition often leads to intellectual disability, developmental delays, and issues with movement and balance. Current treatments primarily involve a combination of anti-seizure medications (ASMs), but achieving good seizure control remains challenging, with few patients experiencing complete seizure freedom. This highlights the significant unmet medical need and the potential impact of new therapies like zorevunersen.
