Metabolism of CJ-036878, N-(3-phenethoxybenzyl)-4-hydroxybenzamide, in liver microsomes and recombinant cytochrome P450 enzymes: metabolite identification by LC-UV/MS(n) and (1)H-NMR.

The identification of metabolites in the early stages of drug discovery is important not only for guiding structure-activity relationships (SAR) and structure-metabolism relationships (SMR) strategies, but also for predicting the potential for adverse events. The present study investigated the phase I metabolism of CJ-036878 (N-(3-phenethoxybenzyl)-4-hydroxybenzamide), a potent antagonist of the N-methyl-D-asparatate (NMDA) receptor, using liver microsomes and representative recombinant cytochrome P450 enzymes. The structures of the oxidative metabolites M1-M11 were confirmed by LC-UV/MS(n) and/or (1)H-nuclear magnetic resonance (NMR). It was found that CJ-036878 is metabolized through three routes: (1) aliphatic hydroxylation that generates M1 and M2; (2) aromatic hydroxylation that produces M3-M5, M7 and M8; and (3) dimerization through an oxidative phenol coupling reaction that yields M10 and M11. The use of recombinant human cytochrome P450 enzymes suggested that CYP3A4 is the major enzyme involved in the oxidative metabolism of CJ-036878, with minor contributions from CYP1A2, CYP2C19, and CYP2D6.