RT Journal Article SR Electronic T1 Biotransformation of the Antiretroviral Drug Etravirine: Metabolite Identification, Reaction Phenotyping and Characterization of Autoinduction of Cytochrome P450-dependent Metabolism JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP dmd.111.044404 DO 10.1124/dmd.111.044404 A1 Lindsay Yanakakis A1 Namandje N Bumpus YR 2012 UL http://dmd.aspetjournals.org/content/early/2012/01/23/dmd.111.044404.abstract AB Etravirine (ETR) is a second-generation non-nucleoside reverse transcriptase inhibitor prescribed for the treatment of HIV-1. Using human liver microsomes (HLMs), cDNA-expressed cytochrome P450s (CYPs) and UDP-glucuronosyltransferases (UGTs) the routes of ETR metabolism were defined. Incubations with cDNA-expressed CYP isozymes and chemical inhibition studies using HLMs indicated that CYP2C19 is primarily responsible for the formation of both the major monohydroxylated and dihydroxylated metabolites of ETR. Tandem mass spectrometry suggested that these metabolites were produced via monomethylhydroxylation and dimethylhydroxylation of the dimethylbenzonitrile moiety. Formation of these monohydroxy and dihydroxy metabolites was decreased by 75% and 100%, respectively, in assays performed using HLMs that were genotyped as homozygous for the loss-of function CYP2C19*2 allele as compared to formation by HLMs genotyped as CYP2C19*1/*1. Two monohydroxylated metabolites of lower abundance were formed by CYP3A4 and interestingly, although CYP2C9 showed no activity towards the parent compound, this enzyme appeared to act in concert with CYP3A4 to form two minor dihydroxylated products of ETR. UGTs 1A3 and 1A8 were demonstrated to glucuronidate a CYP3A4-dependent monohydroxylated product. In addition, treatment of primary human hepatocytes with ETR resulted in 3.2-, 5.2-, 11.8-, and 17.9-fold increases in CYP3A4 mRNA levels 6 h, 12 h, 24 h and 72 h following treatment. The presence of the pregnane X receptor antagonist sulforaphane blocked the ETR-mediated increase in CYP3A4 mRNA expression. Taken together, these data suggest that ETR and ETR metabolites are substrates of CYP2C19, CYP3A4, CYP2C9, UGT1A3 and UGT1A8 and that ETR is a PXR-dependent modulator of CYP3A4 mRNA levels.