Biotransformation of the Antiretroviral Drug Etravirine: Metabolite Identification, Reaction Phenotyping, and Characterization of Autoinduction of Cytochrome P450-Dependent Metabolism

Abstract

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.

Dissimilarities in the metabolism of antiretroviral drugs used in HIV pre-exposure prophylaxis in colon and vagina tissues

“…The third donor (age 28, female) demonstrated a 2.5-fold increase in CYP3A4 mRNA levels with no other changes. It was previously reported that etravirine modulates CYP3A4 expression in a pregnane x receptor (PXR)-dependent manner [10]. With this in mind, PXR mRNA expression in the colon tissues was measured and showed positive correlation with the observed changes in CYP3A4 mRNA, indicating that there may be a relationship between PXR levels and dapivirine-treatment dependent CYP3A4 mRNA expression changes in colon tissue (Figure 9D).…”

Human Biotransformation of the Nonnucleoside Reverse Transcriptase Inhibitor Rilpivirine and a Cross-Species Metabolism Comparison

“…Oxidative metabolism did not appear to be shunted to glucuronic acid conjugation, as the glucuronides that were detectable in the hepatocyte medium, namely, metabolites M5 and M6, also did not exhibit an increase in abundance over the 24 h of incubation. Although we have previously reported that autoinduction of etravirine metabolism is readily detectable following 24 h of incubation with primary human hepatocytes (17), longer treatment times may be required to observe this effect using RPV. For instance, CYP3A4 protein may not have yet been elevated over the time points that we measured.…”

“…A recent report demonstrated that RPV, similar to the nonnucleoside reverse transcriptase inhibitors etravirine and efavirenz, was able to activate the pregnane X receptor in primary human hepatocytes (17). The pregnane X receptor is a key regulator of drug-metabolizing enzymes, including CYP3A and UGT1A isozymes (22)(23)(24).…”

Interaction between Darunavir and Etravirine Is Partly Mediated by CYP3A5 Polymorphism

“…ETR is also a weak inducer of CYP3A4 [16] (by increasing the abundance of CYP3A4 mRNA in a pregnane X receptor (PXR) dependent manner) [17] and an inhibitor of CYP2C9, CYP2C19 and P-gp [15, 16, 18]. It has been previously demonstrated that the CYP3A5 gene is inducible by mechanisms similar to those involved in CYP3A4 induction, involving constitutively activated receptor (CAR) and PXR [19].…”