Radiprodil reduced seizures among people with gain-of-function GRIN Disorders by a median of 86% in a Phase 1B clinical trial, according to GRIN Therapeutics.

The potential treatment also led to clinical improvements in other symptoms, and was well tolerated from a safety perspective.

While there’s still a long road before regulators would even consider approving Radiprodil as a treatment for people living with a GRI Disorder, these results mark a significant milestone in efforts to find treatments and cures for people living with GRI Disorders.

GRIN Therapeutics said 15 people were part of its Phase 1B trial. Everyone in the trial had a gain-of-function GRIN variant – a mix of GRIN1, GRIN2A and GRIN2B Disorders.

Eight of the study participants experienced regular seizures before the trial. But after taking Radiprodil in the trial, seizures were reduced by a median of 86%. This means that four participants saw a reduction of greater than 86% while four saw a reduction of less than 86%. Only one person stopped seizing altogether, but nearly half (43%) saw seizures drop by at least 90%.

Among the broader group of 15 people enrolled in the study, parents and doctors “generally assessed patients as clinically improved” in non-seizure measures, GRIN Therapeutics said.

Dr. Bruce Leuchter, President and Chief Executive Officer at Neurvati Neurosciences and GRIN Therapeutics said the results “provide strong rationale” to move Radiprodil to a Phase 3 clinical trial as quickly as possible.

The company told CureGRIN that any Phase 3 trial would include patients in the United States. The Phase 1B trial took place in Europe and Canada.

While the Phase 1B results are promising, there is no guarantee the drug will receive approval from the FDA and other regulators. Less than half of drugs that make it to a Phase 3 receive approval.

And while all patients received Radiprodil in the Phase 1B trial, it’s expected that up to half of the patients in a Phase 3 trial would be on a placebo drug.

Read more detail in GRIN Therapeutics press release which includes the following quotes:

“The results of this trial are very encouraging as they suggest that Radiprodil has the potential to substantially reduce the occurrence of seizures and possibly improve behaviors in children with gain-of-function mutations who are not responding well to current treatments. Given these initial efficacy data and promising safety profile, we look forward to continuing to advance this important research program into the next phase of development.”

– Prof. Renzo Guerrini, MD, FRCP, FAES, Director, Neuroscience and Human Genetics Department, Phase 1 Clinical Trial Centre, Children’s Hospital A. Meyer IRCCS, University of Florence, Italy. 

“We believe the findings from the Honeycomb study in gain-of-function patients with treatment resistant symptoms provide strong rationale to progress this promising program into Phase 3 development as quickly as possible. I am proud of the progress we have made to address the profound unmet need in GRIN-related neurodevelopmental disorder since we launched the company three years ago with an investment from Blackstone Life Sciences. These compelling data represent the first major milestone in our development plans for Radiprodil and will help us build new levels of momentum toward achieving our goal of bringing the first approved treatment to patients living with GRIN-related neurodevelopmental disorder.”

– Bruce Leuchter, MD, President and Chief Executive Officer at Neurvati Neurosciences and GRIN Therapeutics.