Preclinical characterization of MDL 27,192 as a potential broad spectrum anticonvulsant agent with neuroprotective properties.

The compound 5-(4-chlorophenyl)-2,4-dihydro-4-ethyl-3H-1,2,4-triazol-3-one (MDL 27,192) was evaluated in a variety of rodent models to assess its anticonvulsant profile and its potential neuroprotective activity. MDL 27,192 demonstrated anticonvulsant activity in a wide range of epilepsy models that are genetically-based (audiogenic seizures in the seizure susceptible DBA/2J or Frings mouse; spike wave seizures in genetic absence epilepsy rats of Strasbourg (GAERS), electrically-based (MES seizures in mice and rats, corneally-kindled seizures in rats) and chemically-based (bicuculline, PTZ, picrotoxin, 3-mercaptopropionic acid, quinolinic acid and strychnine). When compared to valproate, orally administered MDL 27,192 was 17-48-fold more potent as an anticonvulsant and showed a safety index one to three-fold greater. Following a timed intravenous administration of PTZ to mice, MDL 27,192, but not phenytoin or carbamazepine, consistently increased the latencies to first twitch and clonus. MDL 27,192 was active in a genetic model of absence epilepsy, the GAERS rat model. These data indicate that MDL 27,192 likely exerts its anticonvulsant action by affecting seizure spread and by raising seizure threshold. MDL 27,192 did not display any signs of tolerance following subchronic (15 day) administration. In tests of neuroprotective potential, MDL 27,192 reduced infarct volume in a permanent middle cerebral artery occlusion model of focal cerebral ischemia in rats and reduced the loss of hippocampal dentate hilar neurons in an animal model of unilateral head injury. In summary, MDL 27,192 possesses a broad-spectrum anticonvulsant profile. The potential for reduced tolerance and neuroprotective activity are additional positive features of MDL 27,192's preclinical profile.