Abstract
Maraviroc is an anti-human immunodeficiency virus drug that acts by blocking viral entry into target cells. With use of ultra-performance liquid chromatography-mass spectrometry several monooxygenated, dioxygenated, and glucuronidated metabolites of maraviroc were identified both in vitro and in vivo. Characterization of the enzymes involved in the production of these metabolites determined that cytochrome P450 3A5 was the principal enzyme responsible for the formation of an abundant metabolite of maraviroc that resulted from oxygenation of the dichlorocyclohexane ring. For the formation of this metabolite, the V(max) values for CYP3A4 and CYP3A5 were 0.04 and 0.93 pmol · min⁻¹ · pmol P450⁻¹, and the K(m) values were 11.1 and 48.9 μM, respectively. Furthermore, human liver microsomes isolated from donors homozygous for the loss-of-function CYP3A5*3 allele exhibited a 79% decrease in formation of this metabolite compared with those homozygous for the wild-type CYP3A5*1 allele. To probe which divergent residues between CYP3A4 and CYP3A5 might play a role in the differential activities of these enzymes toward maraviroc, mutations were introduced into both enzymes and metabolism of maraviroc was measured. A CYP3A5 L57F mutant exhibited a 61% decrease in the formation of this metabolite, whereas formation by a CYP3A4 F57L mutant was increased by 337% compared with that of the wild type. Taken together, these data provide novel insights into the biotransformation of maraviroc as well as the potential role of CYP3A4 and CYP3A5 divergent residues in the enzymatic activities of these two highly homologous enzymes.