Dataset Information

Glucuronidation of the antiretroviral drug efavirenz by UGT2B7 and an in vitro investigation of drug-drug interaction with zidovudine.

ABSTRACT: The non-nucleoside reverse transcriptase inhibitor efavirenz (EFV) is directly conjugated by the UDP-glucuronosyltransferase (UGT) pathway to form EFV-N-glucuronide (EFV-G), but the enzyme(s) involved has not yet been identified. The glucuronidation of EFV was screened with UGT1A and UGT2B enzymes expressed in a heterologous system, and UGT2B7 was shown to be the only reactive enzyme. The apparent K(m) value of UGT2B7 (21 microM) is similar to the value observed for human liver microsomes (24 microM), whereas the variant allozyme UGT2B7*2 (Tyr(268)) displayed similar kinetic parameters. Because 3'-azido-3'-deoxythymidine (AZT), one of the most current nucleotide reverse transcriptase inhibitors prescribed in combination with EFV, is also conjugated by UGT2B7, the potential metabolic interaction between EFV and AZT has been studied using human liver microsomes. Glucuronidation of both drugs was inhibited by one another, in a concentration-dependent manner. At K(m) values (25 and 1000 microM for EFV and AZT, respectively), EFV inhibited AZT glucuronidation by 47%, whereas AZT inhibited EFV glucuronidation by 23%. With a K(i) value of 17 microM for AZT-glucuronide formation, EFV appears to be one of the most selective and potent competitive inhibitor of AZT glucuronidation in vitro. Moreover, assuming that concentrations of EFV achieved in plasma (C(max) = 12.9 microM) are in a range similar to its K(i) value, it was estimated that EFV could produce a theoretical 43% inhibition of AZT glucuronidation in vivo. We conclude that UGT2B7 has a major role in EFV glucuronidation and that EFV could potentially interfere with the hepatic glucuronidation of AZT.

SUBMITTER: Belanger AS

PROVIDER: S-EPMC2729325 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Glucuronidation of the antiretroviral drug efavirenz by UGT2B7 and an in vitro investigation of drug-drug interaction with zidovudine.

Bélanger Anne-Sophie AS Caron Patrick P Harvey Mario M Zimmerman Peter A PA Mehlotra Rajeev K RK Guillemette Chantal C

Drug metabolism and disposition: the biological fate of chemicals 20090601 9

The non-nucleoside reverse transcriptase inhibitor efavirenz (EFV) is directly conjugated by the UDP-glucuronosyltransferase (UGT) pathway to form EFV-N-glucuronide (EFV-G), but the enzyme(s) involved has not yet been identified. The glucuronidation of EFV was screened with UGT1A and UGT2B enzymes expressed in a heterologous system, and UGT2B7 was shown to be the only reactive enzyme. The apparent K(m) value of UGT2B7 (21 microM) is similar to the value observed for human liver microsomes (24 mi ...[more]

PMID: 19487252

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Project description:Uridine diphosphate-glucuronosyltransferase (UGT) 2B7 is expressed mostly in the human liver, lung and kidney and can transfer endogenous glucuronide group into its substrate and impact the pharmacological effects of several drugs such as estriol, AZT and morphine. UGT2B7 and its allelic variants can dimerize with the homologous enzymes UGT1A1 and UGT1A9, as well as their allelic variants, and then change their enzymatic activities in the process of substrate catalysis. The current study was designed to identify this mechanism using morphine as the substrate of UGT2B7. Single-recombinant allozymes, including UGT2B7*1 (wild type), UGT2B7*71S (A71S, 211G>T), UGT2B7*2 (H268Y, 802C>T), UGT2B7*5 (D398N, 1192G>A), and double-recombinant allozymes formed by the dimerization of UGT1A9*1 (wild type), UGT1A9*2 (C3Y, 8G>A), UGT1A9*3 (M33T, 98T>C), UGT1A9*5 (D256N, 766G>A), UGT1A1 (wild type) with its splice variant UGT1A1b were established and incubated with morphine in vitro. Each sample was analyzed with HPLC-MS/MS. All enzyme kinetic parameters were then measured and analyzed. From the results, the production ratio of its aberrant metabolism and subsequent metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), changes regioselectively. Double-recombinant allozymes exhibit stronger enzymatic activity catalyzing morphine than the single-recombinant alloyzymes. Compared to UGT2B7*1, UGT2B7*2 singles or doubles have lower Km values for M3G and M6G, whereas UGT2B7*5 allozymes perform opposite effects. The double allozymes of UGT1A9*2 or UGT1A9*5 with UGT2B7 tend to produce M6G. Interestingly, the majority of single or double allozymes significantly reduce the ratio of M3G to M6G. The UGT1A9*2-UGT2B7*1 double enzyme has the lowest M3G:M6G ratio, reflecting that more M6G would form in morphine glucuronide metabolism. This study demonstrates that UGT2B7 common SNPs and their dimers with UGT1A1 and UGT1A9 and their allelic variants can regioselectively affect the generation of two metabolites of morphine via altering the CLint ratios of M3G to M6G. These results may predict the effectiveness of morphine antinociception in individualized opioid treatment.

Dataset Information

Glucuronidation of the antiretroviral drug efavirenz by UGT2B7 and an in vitro investigation of drug-drug interaction with zidovudine.

Publications

Glucuronidation of the antiretroviral drug efavirenz by UGT2B7 and an in vitro investigation of drug-drug interaction with zidovudine.

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