Abstract
Etravirine (ETR) is a second-generation non-nucleoside reverse transcriptase inhibitor prescribed for the treatment of HIV-1. By using human liver microsomes (HLMs), cDNA-expressed cytochromes P450 (P450s), and UDP-glucuronosyltransferases (UGTs), the routes of ETR metabolism were defined. Incubations with cDNA-expressed P450 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 compared with 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 toward the parent compound, this enzyme appeared to act in concert with CYP3A4 to form two minor dihydroxylated products of ETR. UGT1A3 and UGT1A8 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, 12, 24, and 72 h after 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.
Footnotes
This work was supported by the PhRMA Foundation (Research Starter Grant in Pharmacology/Toxicology; to N.N.B.). The AB SCIEX QTRAP 5500 mass spectrometer was purchased using a grant from the National Institutes of Health National Center for Research Resources [Grant 1S10-RR27733]; the Waters Acquity ultraperformance liquid chromatograph interfaced with the AB SCIEX QTRAP 5500 mass spectrometer was purchased with funds provided by the Pendleton Foundation Trust.
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
ABBREVIATIONS:
- HIV
- human immunodeficiency virus
- NNRTI
- non-nucleoside reverse transcriptase inhibitor
- ETR
- etravirine
- P450
- cytochrome P450
- UGT
- UDP-glucuronosyltransferase
- HLM
- human liver microsomes
- PXR
- pregnane X receptor
- PPP
- 2-phenyl-2-(1-piperidinyl)propane
- SFN
- sulforaphane
- RIF
- rifampin
- UDPGA
- UDP-glucuronic acid
- UPLC-MS
- ultraperformance liquid chromatography-mass spectrometry
- DMSO
- dimethyl sulfoxide
- TIS
- TurboIonSpray
- MS/MS
- tandem mass spectrometry
- PCR
- polymerase chain reaction
- qPCR
- quantitative polymerase chain reaction
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase.
- Received December 20, 2011.
- Accepted January 23, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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