Utility of non-human primates in drug development: Comparison of non-human primate and human drug-metabolizing cytochrome P450 enzymes

Cynomolgus monkeys (Macaca fascicularis, an Old World Monkey) have been widely used as a non-human primate model in preclinical studies because of their genetic and physiological similarity to humans. This trend has been followed by common marmoset (Callithrix jacchus, a New World Monkey). However, drug-metabolism properties in these non-human primates have not been fully understood due to limited information on cytochrome P450 (P450) enzymes, major drug-metabolizing enzymes in humans. Multiple forms of cynomolgus monkey P450 enzymes have been identified and characterized in comparison to those of humans, including a cynomolgus monkey specific form, P450 2C76. Similarly, marmoset P450 1A/B, 2A, 2C, 2D, and 4F enzymes were recently identified and characterized to understand drug metabolism properties. In this research update, updates for marmoset, cynomolgus monkey, and human P450 cDNAs are provided. Marmoset and cynomolgus monkey P450 enzymes showed high sequence homology to their human counterparts and generally had similar substrate recognition functionality to human P450 enzymes; however, they also possibly contribute to limited specific differences in drug oxidative metabolism partly due to small differences in amino acid residues. These findings provide a foundation for successful use of non-human primates as preclinical models and will help to further understand molecular mechanisms of human P450 function. In addition to the P450 enzymes, flavin-containing monooxygenases, another monooxygenase family, in these non-human primates have been found to be involved in the oxidation of a variety of compounds associated with pharmacological and/or toxicological effects in humans and are also described.