Do in vitro assays in rat primary neurons predict drug-induced seizure liability in humans?

Drug-induced seizures contribute to the high attrition rate of pharmaceutical compounds in development. The assessment of drug-induced seizure liability generally occurs in later phases of development using low throughput and intensive in vivo assays. In the present study, we evaluated the potential of an in vitro assay for detecting drug-induced seizure risk compared to evaluation in rats in vivo. We investigated the effects of 8 reference drugs with a known seizurogenic risk using micro-electrode array (MEA) recordings from freshly-dissociated rat primary neurons cultured on 48-well dishes for 28 days, compared to their effects on the EEG in anesthetized rats. In addition, we evaluated functional responses and mRNA expression levels of different receptors in vitro to understand the potential mechanisms of drug-induced seizure risk. Combining the functional MEA in vitro data with concomitant gene expression allowed us to identify several potential molecular targets that might explain the drug-induced seizures occurring in both rats and humans. Our data 1) demonstrate the utility of a group of MEA parameters for detecting potential drug-induced seizure risk in vitro; 2) suggest that an in vitro MEA assay with rat primary neurons may have advantages over an in vivo rat model; and 3) identify potential mechanisms for the discordance between rat assays and human seizure risk for certain seizurogenic drugs.