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

Abstract

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/MSⁿ and/or ¹H-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.

Key Words::

• Cytochrome P450
• phenol oxidative coupling
• dimerization
• CYP3A4

Acknowledgements

The authors thank Drs Masami Nakane, Mitsuhiro Kawamura, Kaoru Shimada, and Mamoru Uchiyama for their helpful discussions and advice. They also thank Ms Miyako Matsumizu for synthesizing the parent compound CJ-036878.