GRIN Therapeutics announced today that its investigational drug radiprodil has received Breakthrough Therapy designation from the U.S. Food and Drug Administration for treating seizures in patients with GRIN-related neurodevelopmental disorder (GRIN-NDD) with gain-of-function mutations.
Promising Clinical Results Drive Breakthrough Status
The designation was supported by compelling data from the Phase 1b Honeycomb study, which demonstrated remarkable efficacy in pediatric patients. Treatment with radiprodil led to an 86% median reduction in countable motor seizure frequency compared to baseline. Notably, 71% of patients experienced greater than 50% reduction in seizures, with six out of seven patients achieving seizure-free status during at least 80% of the eight-week maintenance period.
"The FDA's decision to designate radiprodil as a Breakthrough Therapy underscores its potential as a treatment option for patients who currently have no approved therapies," said Bruce Leuchter, MD, President and Chief Executive Officer at Neurvati Neurosciences and GRIN Therapeutics.
Mechanism of Action and Disease Impact
Radiprodil functions as a selective and potent negative allosteric modulator of the N-methyl-D-aspartate (NMDA) receptor subtype 2B (NR2B or GluN2B). This targeted approach addresses the underlying disease biology of GRIN-NDD, a rare genetic disorder that typically presents in infancy and causes developmental delays, intellectual disabilities, epilepsy, and various motor and behavioral challenges.
Clinical Development Path
Professor Jacqueline A. French, MD, from NYU Grossman School of Medicine and member of GRIN Therapeutics' Clinical Advisory Committee, emphasized the significance of the breakthrough designation: "The increased engagement with FDA will ensure that the radiprodil program, developed in partnership with the academic and advocacy communities, has the best chance of success."
Safety Profile and Additional Benefits
The Phase 1b trial showed radiprodil to be generally well-tolerated, with adverse events primarily related to infections or underlying disease symptoms. Beyond seizure control, patients demonstrated broader clinical improvements, as measured by Clinician and Caregiver Global Impressions of Change and the Aberrant Behavior Checklist – Community.
Moving Forward
GRIN Therapeutics plans to initiate Phase 3 pivotal trials in mid-2025, supported by a $200M capital commitment from Blackstone Life Sciences. The upcoming study will evaluate radiprodil's impact on core disease aspects, including seizures, behavioral abnormalities, and functional outcomes.
The Breakthrough Therapy designation grants radiprodil access to expedited development and review processes, including intensive FDA guidance and organizational commitment from senior managers, potentially accelerating its path to patients who currently lack approved treatment options.
