TY - JOUR T1 - Comparative Biotransformation of Pyrazinone-Containing Corticotropin-Releasing Factor Receptor-1 Antagonists: Minimizing the Reactive Metabolite Formation JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 5 LP - 15 DO - 10.1124/dmd.109.028910 VL - 38 IS - 1 AU - Xiaoliang Zhuo AU - Richard A. Hartz AU - Joanne J. Bronson AU - Harvey Wong AU - Vijay T. Ahuja AU - Vivekana M. Vrudhula AU - John E. Leet AU - Stella Huang AU - John E. Macor AU - Yue-Zhong Shu Y1 - 2010/01/01 UR - http://dmd.aspetjournals.org/content/38/1/5.abstract N2 - (S)-5-Chloro-1-(1-cyclopropylethyl)-3-(2,6-dichloro-4-(trifluoromethyl)phenylamino)pyrazin-2(1H)-one (BMS-665053), a pyrazinone-containing compound, is a potent and selective antagonist of corticotropin-releasing factor receptor-1 (CRF-R1) that showed efficacy in the defensive withdrawal model for anxiety in rats, suggesting its use as a potential treatment for anxiety and depression. In vitro metabolism studies of BMS-665053 in rat and human liver microsomes revealed cytochrome P450-mediated oxidation of the pyrazinone moiety, followed by ring opening, as the primary metabolic pathway. Detection of a series of GSH adducts in trapping experiments suggested the formation of a reactive intermediate, probably as a result of epoxidation of the pyrazinone moiety. In addition, BMS-665053 (20 mg/kg i.v.) underwent extensive metabolism in bile duct-cannulated (BDC) rats. The major drug-related materials in rat plasma were the pyrazinone oxidation products. In rat bile and urine (0–7 h), only a trace amount of the parent drug was recovered, whereas significant levels of the pyrazinone epoxide-derived metabolites and GSH-related conjugates were detected. Further evidence suggested that GSH-related conjugates also formed at the dichloroarylamine moiety possibly via an epoxide or a quinone imine intermediate. Other major metabolites in BDC rat bile and urine included glucuronide conjugates. To reduce potential liability due to metabolic activation of BMS-665053, a number of pyrazinone analogs with different substituents were synthesized and investigated for reactive metabolite formation, leading to the discovery of a CRF-R1 antagonist with diminished in vitro metabolic activation. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics ER -