Comparative In Vitro And In Vivo Metabolism Of Mpc-3100, An Oral Hsp90 Inhibitor, In Rat, Dog, Monkey And Human

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL MPC-3100, an 8, 9-disubstituted purine, is an orally bioavailable HSP90 inhibitor currently in Phase 1 clinical development. The objectives of these studies were to compare the metabolism of MPC-3100 in preclinical species to select the species most appropriate for toxicological testing and to identify the major phase I and II metabolites formed both in vitro and in vivo in rats, dogs, monkeys and humans. MPC-3100 was incubated with liver microsomes from rats, dogs, monkeys, and humans. In addition, urine, feces, and bile were collected from rats dosed with MPC-3100 intravenously (5 mg/kg) or orally (50 mg/kg), and urine was collected from dogs (2 mg/kg) and cynomolgus monkeys (2.5 mg/kg) dosed intravenously. Metabolites were identified by liquid chromatography electrospray-ionization mass spectrometry. Quantitative analysis was performed with an AB Sciex 4000 Q-trap and qualitative analysis was conducted on a high resolution Agilent Q-TOF 6520 mass spectrometer. Six authentic standards were synthesized and used to confirm structural identity. In human liver microsomes, four distinct peaks were observed following chromatographic analysis. Three of these were conclusively identified using synthetic standards, accurate mass, and chromatographic retention time. The most abundant metabolite in all species was the catechol. In human, monkey, and dog liver microsomes, the next most abundant metabolite was formed by oxidation of the 2-hydroxypropan-1-one moiety to propane-1, 2-dione. A third metabolite present in all incubations was the de-amidated product of MPC-3100. It was formed in microsomes in the absence of NADPH suggesting that its formation was due to pH-mediated hydrolysis. A fourth metabolite formed by the addition of oxygen (+16 Da) within the methylenedioxyphenyl ring was assigned based solely upon its product ion spectrum. Following intravenous administration of MPC-3100 to rats, fourteen metabolites were observed in the feces; whereas, only 6 metabolites were observed in urine. No glucuronides were found in either the urine or feces. Less than 1% of the dose was recovered in rat urine; whereas, up to 40% of the dose was recovered as MPC-3100 and metabolites in feces over a 24 hour period. As many as 25 different metabolites were observed in the bile based upon differences in their retention time and molecular weight. Most of the metabolites in the bile resulted from either glucuronidation or sulfation, some of which were conclusively identified with authentic standards. Rat, dog, and monkey liver microsomes all produced the four major metabolites formed in human liver microsomes. Three of these metabolites formed in human microsomes were conclusively identified by comparison to authentic synthetic standards. Although MPC-3100 and several metabolites were found in rat, dog and monkey urine, the primary route of elimination of MPC-3100 was through biliary excretion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3233. doi:10.1158/1538-7445.AM2011-3233