INTERSPECIES VARIABILITY OF TNP-470 METABOLISM, USING PRIMARY MONKEY,RAT, AND DOG CULTURED-HEPATOCYTES

The biotransformation of TNP-470 [O-(chloroacetylcarbamoyl)fumagillol; AGM 1470], a potent in vitro inhibitor of angiogenesis, was investiga ted in primary cultured hepatocytes isolated from different species, i ncluding monkey, dog, and rat, as well as in microsomal fractions of v arious monkey tissues. previous metabolic studies by our group using h uman hepatocytes in primary culture demonstrated that TNP-470 was prim arily metabolized to M-IV through an ester cleavage, with subsequent c onversion of M-IV to M-ll by microsomal epoxide hydrolase. Additional studies using monkey liver microsomes demonstrated that M-II was then glucuronidated by uridine-5'-diphosphoglucuronyl transferase, leading to the formation of M-lll. Three other, as yet unidentified, metabolit es, labeled M-l, M-V, and M-VI, were also detected. Similarly to findi ngs in human hepatocytes, the predominant extracellular metabolite was M-ll in all species studied. Minor interspecies variability was obser ved in the total amount of drug biotransformed by hepatocytes, but som e variability was detected in the metabolic pattern of TNP-470 in monk ey hepatocytes, compared with rat or dog hepatocytes. In monkey hepato cytes, as previously observed in human cells, TNP-470 was metabolized to six derivatives, labeled M-l, M-II, M-lll, M-IV, M-V, and M-VI, whe reas the latter metabolite was not observed in dog or rat extracellula r medium. Extrahepatic metabolism of TNP-470 was also studied using mo nkey intestine, kidney, and lung microsomes, which demonstrated that, under these experimental conditions, TNP-470 was extensively metaboliz ed to four derivatives, i.e. M-l, M-ll, M-Ill, and M-IV, with M-Ill be ing detected only in liver samples. These studies suggest that the met abolism of TNP-470 in monkeys appears to be most closely related to th at observed in humans. Although the individual quantitative metabolic profiles were quite different in various animal species, only one meta bolite, namely M-VI, was not detected in either dog or rat hepatocytes in vitro.