Physiological disposition and metabolism of L-365,260, a potent antagonist of brain cholecystokinin receptor, in laboratory animals.

L-365,260 [3R(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4- benzodiazepine-3-yl)-N'-(3-methylphenylurea)], a potent nonpeptide antagonist of the CCKB receptor, is currently under investigation to treat anxiety and panic disorders. This study describes absorption and disposition of the drug in rats, dogs, and monkeys. Following iv administration (5 mg/kg), L-365,260 was cleared very rapidly in rats, dogs, and monkeys. In all species, the concentrations of the drug in plasma declined in a polyphasic manner. There was no difference in total blood clearance among species, whereas considerable species differences were observed in volume of distribution and terminal half-lives. Binding of 14C-L-365,260 to plasma protein was extensive for all test species (greater than 96%). Interspecies differences in absorption were also observed. The bioavailability for rats, dogs, and monkeys was approximately 14%, 9%, and 2%, respectively. HPLC radiohistograms of urine and bile revealed that only trace amounts of intact drug were present; the drug was mainly eliminated by biotransformation. NMR and mass spectral analyses indicate that hydroxylation and glucuronide conjugation are the major biotransformation pathways.