In Vitro to In Vivo Screening Across Model Systems Uncovers a New GABA Receptor Modulator for Seizures

The use of "New Approach Methods" (NAMs) is increasingly being implemented in early therapy discovery as a means to ensure that animal testing will be reduced, refined, or potentially altogether replaced in the future. NAMs can include in vitro human-based systems, in silico modeling, or other cellular-based assays that do not require animal testing.

NAMs move us closer to the 3Rs principles that have been advocated core principle of preclinical research since 1959. In 2025, the US FDA outlined a roadmap for all IND applications to include NAMs wherever feasible, and in particular for toxicology testing. Yet how various NAMs can be applied for antiseizure therapy discovery is less well-defined. 

Epilepsy is a network disorder - epileptiform activity can certainly be reproduced in cell-based assays in a dish, but epilepsy is MORE than just seizures. Epilepsy is a chronic disease that is defined by spontaneous recurrent seizures, as well as cognitive and neuropsychiatric symptoms that are at times more burdensome to the patient's quality of life than the seizures themselves. Unfortunately, NAMs still have a long way to go in reproducing these non-seizure symptoms. And NAMs cannot yet tell us how likely a newly identified therapeutic is to being effective in human epilepsy patients. 

To fill this gap, we sought to implement a compound library screening campaign in several reduced systems - zebrafish and nematodes - to identify a potential hit. Then, we confirmed the antiseizure effects of our hit compound, chlorothymol, in the most common and clinically validated mouse seizure models. Finally, we confirmed the molecular mechanism of this compound in both mouse and human brain slice assays to confirm electrophysiological effects. 

In short, we provide some of the first evidence that a novel, multiorganismal drug screening platform that integrates NAMs in line with traditional and validated rodent seizure models can be useful to identify new promising investigational therapies for people with epilepsy.