title: In vitro metabolism and drug-drug interaction potential of UTL-5g, a novel chemo- and radioprotective agent.
abstract: N-(2,4-dichlorophenyl)-5-methyl-1,2-oxazole-3-carboxamide (UTL-5g), a potential chemo- and radioprotective agent, acts as a prodrug requiring bioactivation to the active metabolite 5-methylisoxazole-3-carboxylic acid (ISOX). UTL-5g hydrolysis to ISOX and 2,4-dichloroaniline (DCA) has been identified in porcine and rabbit liver esterases. The purpose of this study was to provide insights on the metabolism and drug interaction potential of UTL-5g in humans. The kinetics of UTL-5g hydrolysis was determined in human liver microsomes (HLM) and recombinant human carboxylesterases (hCE1b and hCE2). The potential of UTL-5g and its metabolites for competitive inhibition and time-dependent inhibition of microsomal cytochrome P450 (P450) was examined in HLM. UTL-5g hydrolysis to ISOX and DCA in HLM were NADPH-independent, with a maximum rate of reaction (Vmax) of 11.1 nmol/min per mg and substrate affinity (Km) of 41.6 µM. Both hCE1b and hCE2 effectively catalyzed UTL-5g hydrolysis, but hCE2 exhibited ∼30-fold higher catalytic efficiency (Vmax/Km) than hCE1b. UTL-5g and DCA competitively inhibited microsomal CYP1A2, CYP2B6, and CYP2C19 (IC50 values <50 µM), and exhibited time-dependent inhibition of microsomal CYP1A2 with the inactivation efficiency (kinact/KI) of 0.68 and 0.51 minute(-1)·mM(-1), respectively. ISOX did not inhibit or inactivate any tested microsomal P450. In conclusion, hCE1b and hCE2 play a key role in the bioactivation of UTL-5g. Factors influencing carboxylesterase activities may have a significant impact on the pharmacological and therapeutic effects of UTL-5g. UTL-5g has the potential to inhibit P450-mediated metabolism through competitive inhibition or time-dependent inhibition. Caution is particularly needed for potential drug interactions involving competitive inhibition or time-dependent inhibition of CYP1A2 in the future clinical development of UTL-5g.
authors.affiliation: Karmanos Cancer Institute, Department of Oncology (J.W., J.L.), and Department of Pharmacology (S.D.), Wayne State University School of Medicine, Detroit, Michigan; 21 Century Therapeutics, Inc., Ferndale, Michigan (J.S.); and Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan (F.V.).
authors.forename: Jianmei
authors.initials: J
authors.lastname: Wu
authors.affiliation: Karmanos Cancer Institute, Department of Oncology (J.W., J.L.), and Department of Pharmacology (S.D.), Wayne State University School of Medicine, Detroit, Michigan; 21 Century Therapeutics, Inc., Ferndale, Michigan (J.S.); and Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan (F.V.).
authors.forename: Jiajiu
authors.initials: J
authors.lastname: Shaw
authors.affiliation: Karmanos Cancer Institute, Department of Oncology (J.W., J.L.), and Department of Pharmacology (S.D.), Wayne State University School of Medicine, Detroit, Michigan; 21 Century Therapeutics, Inc., Ferndale, Michigan (J.S.); and Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan (F.V.).
authors.forename: Sarah
authors.initials: S
authors.lastname: Dubaisi
authors.affiliation: Karmanos Cancer Institute, Department of Oncology (J.W., J.L.), and Department of Pharmacology (S.D.), Wayne State University School of Medicine, Detroit, Michigan; 21 Century Therapeutics, Inc., Ferndale, Michigan (J.S.); and Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan (F.V.).
authors.forename: Frederick
authors.initials: F
authors.lastname: Valeriote
authors.affiliation: Karmanos Cancer Institute, Department of Oncology (J.W., J.L.), and Department of Pharmacology (S.D.), Wayne State University School of Medicine, Detroit, Michigan; 21 Century Therapeutics, Inc., Ferndale, Michigan (J.S.); and Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan (F.V.) lijin@karmanos.org.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
mesh_terms: D043182:Carboxylesterase / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004347:Drug Interactions / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007555:Isoxazoles / Q000378:metabolism*; D007700:Kinetics; D008862:Microsomes, Liver / Q000378:metabolism*; D011837:Radiation-Protective Agents / Q000378:metabolism*
chemical_list: D007555:Isoxazoles; D011837:Radiation-Protective Agents; C559524:UTL-5g compound; D003577:Cytochrome P-450 Enzyme System; D043182:Carboxylesterase