Assessment of specificity of eight chemical inhibitors using cDNA-expressed cytochromes P450

Sai, Yang; Dai, Renke; Yang, Taoxi; Krausz, Kristopher W.; Gonzalez, Frank J.; Gelboin, Harry V.; Shou, Magang

doi:10.1080/004982500237541

Cited by 123 publications

(90 citation statements)

References 23 publications

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“…However, this approach cannot distinguish between the intestinal availability and the fraction absorbed. Ketoconazole is an antifungal agent that is one of the most potent CYP3A inhibitors both in vitro and in vivo (Olkkola et al, 1994;Tsunoda et al, 1999;Sai et al, 2000). Because the plasma protein binding ratio of ketoconazole is high (99%), it is an appropriate compound to selectively inhibit intestinal metabolism of CYP3A substrates before entering the blood flow (Heel et al, 1982).…”

Section: Introductionmentioning

confidence: 99%

Prediction of the Intestinal First-Pass Metabolism of CYP3A Substrates in Humans Using Cynomolgus Monkeys

Nishimuta¹,

Sato²,

Mizuki³

et al. 2010

Drug Metab Dispos

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ABSTRACT:To select high bioavailability compounds, it is necessary to predict the first-pass metabolism in the intestine. However, in vitro-in vivo predictions of the intestinal metabolism have proven both challenging and less definitive. The purpose of this study was to investigate prediction of intestinal first-pass metabolism in humans using cynomolgus monkeys. First, we investigated intrinsic metabolic activities in intestinal microsomes of monkeys (MIM) and humans (HIM) (CL int, MIM and CL int, HIM , respectively) of 18 CYP3A substrates. The CL int, MIM values were found to be relatively high and showed excellent correlation with the CL int, HIM values. Subsequently, we determined the plasma concentrations of 9 CYP3A substrates (buspirone, carbamazepine, diazepam, felodipine, midazolam, nicardipine, nifedipine, saquinavir, and verapamil) in monkeys after an oral dose of 2 mg/kg with or without an oral dose of 5 mg/kg ketoconazole and calculated AUC (؉vehicle) /AUC (؉ketoconazole) , defined as F g, monkey(observed) ; we confirmed that the dose of ketoconazole inhibited only intestinal CYP3A metabolism by preliminary in vitro and in vivo experiments using ketoconazole. The F g, monkey(observed) was lower than the F g, human(observed) for most compounds, but moderate correlation was observed. Furthermore, using these data, we established a new methodology to estimate F g, human(predicted) more precisely on the basis of the assumption that intestinal physiological conditions other than intrinsic metabolic activity would be the same between monkeys and humans. In conclusion, the in vivo model using cynomolgus monkeys in this study is useful for prediction of intestinal first-pass metabolism by CYP3A in humans because it was able to predict F g, human of all nine compounds investigated.

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Section: Introductionmentioning

confidence: 99%

Prediction of the Intestinal First-Pass Metabolism of CYP3A Substrates in Humans Using Cynomolgus Monkeys

Nishimuta¹,

Sato²,

Mizuki³

et al. 2010

Drug Metab Dispos

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“…DDC, a purported CYP2E1 inhibitor, was also shown to inhibit 18-HC formation by approximately 25 and 50% at concentrations of K 1 and 10K i , respectively. However, DDC has been shown to lack selectivity for CYP2E1 (Eagling et al, 1998;Sai et al, 2000). However, a more selective CYP2E1 inhibitor is currently not available (e.g., diallyldisulfide) (Bourrie et al, 1996).…”

Section: Discussionmentioning

confidence: 99%

Metabolism of 18-Methoxycoronaridine, an Ibogaine Analog, to 18-Hydroxycoronaridine by Genetically Variable CYP2C19

Zhang¹,

Ramamoorthy²,

Tyndale³

et al. 2002

Drug Metab Dispos

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This article is available online at http://dmd.aspetjournals.org ABSTRACT:18-Methoxycoronaridine, a newly developed ibogaine analog, has been reported to decrease the self-administration of morphine, cocaine, ethanol, and nicotine. It has also been reported to attenuate naltrexone-precipitated signs of morphine withdrawal. In this study, three metabolites of 18-methoxycoronaridine (18-MC) were separated and identified by high-performance liquid chromatography-electrospray ionization-mass spectrometry-mass spectrome- try (HPLC-ESI-MS-MS); the major metabolite was 18-hydroxycoronaridine (18-HC). The other two metabolites were elucidated as hydroxylated metabolites on the basis of their MS-MS spectra. Catalytic studies of 18-MC

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“…The inhibitory effect of ketoconazole is relatively CYP3A-specific at low concentrations (Յ1 mM). [13][14][15] On average, the relative contribution of CYP3A to the 2-hydroxylation of EE 2 human liver microsomes is estimated to be approximately 50%. These findings support previous studies 3,4) that showed that, in addition to CYP3A, other multiple P450s also play important roles in EE 2 2-hydroxylation in human liver microsomes.…”

Section: Discussionmentioning

confidence: 99%

“…Inhibition of EE 2 2-Hydroxylase Activities by Ketoconazole The effect of ketoconazole, a potent CYP3A inhibitor, [13][14][15] on EE 2 2-hydroxylase activity was examined in 27 individual human liver microsomes, which showed relatively high EE 2 2-hydroxylase activities among 35 individuals. Ketoconazole was dissolved in 50% methanol, and 3 ml of the solution was added to the incubation mixture (a final concentration of 1 mM).…”

Section: Interindividual Variability In 2-hydroxylation 3-sulfationmentioning

confidence: 99%

Interindividual Variability in 2-Hydroxylation, 3-Sulfation, and 3-Glucuronidation of Ethynylestradiol in Human Liver

Shiraga

Niwa

Ohno

et al. 2004

Biological & Pharmaceutical Bulletin

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Ethynylestradiol (EE 2 ) is commonly used as the major estrogenic component in many oral contraceptive formulations. Orme et al. 1) reported that EE 2 is metabolized by multiple pathways, and there is a large interindividual variability in the routes and rates of metabolism of EE 2 in humans. In addition, marked interindividual differences in the pharmacokinetic parameters of EE 2 have been reported.1) The reported systemic bioavailability of orally ingested EE 2 ranges from 20 to 65%. 1) Factors that could affect oral clearance of a drug include absorption from the gastrointestinal tract, protein binding, intrinsic hepatic clearance, hepatic blood flow, and renal clearance. Urinary excretion of unchanged EE 2 was very low, 2) suggesting that EE 2 is mainly eliminated by metabolism. The 2-hydroxylation of EE 2 is mainly catalyzed by CYP3A, CYP2C, and CYP2E enzymes, 3,4) and this route is one of the main metabolic pathways in humans.5,6) Additionally, sulfation and glucuronidation also play important roles in the metabolism of EE 2 . EE 2 -3-glucuronide and EE 2 -3-sulfate are eliminated into the gastrointestinal tract, hydrolyzed by gut bacteria to EE 2 , and subsequently reabsorbed. Rifampicin, an inducer of CYP3A, has been reported to significantly increase the oral clearance of EE 2 .7) This interaction is thought to reflect the significant contribution of CYP3A enzymes to the metabolism of EE 2 . It is well known that there are large interindividual differences in the expression levels and catalytic activities of CYP3A enzymes in human liver. 8)Patki et al. 9) indicated that the intrinsic clearance of triazolam, a CYP3A substrate, and CYP3A protein in human liver are reduced in the elderly.In vitro studies are useful for clarifying the role of respective enzymes on the systemic drug clearance. Plasma concentrations of EE 2 achieved during normal therapy are very low (Ͻ2 nM).7) However, most previous in vitro studies used substantially high EE 2 substrate concentrations (Ͼ10 mM). A recent study using human hepatocytes in vitro at a substrate concentration of 1 nM demonstrated that the major EE 2 metabolites are direct conjugates, with hydroxylation representing minor pathways, and suggested that the production of EE 2 -3-sulfate was increased by pretreatment of hepatocytes with rifampicin.10) The initial rate of conjugate formation was reported to be EE 2 -3-sulfateϾEE 2 -3-glucuronide in human hepatocytes. 10) In the current study, we investigated interindividual variability of the 2-hydroxylation, 3-glucuronidation, and 3-sulfation of EE 2 using human liver microsomes and cytosol in the presence of the respective cofactors. Additionally, interindividual variability of the relative contribution of CYP3A to the 2-hydroxylation of EE 2 in human liver microsomes was estimated from the degree of inhibition by ketoconazole, a potent inhibitor of CYP3A. All enzyme activities were measured at an EE 2 substrate concentration of 0.1 mM, which is under a nearly linear condition (Ͻ1/23 of K m values for the respectiv...

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Assessment of specificity of eight chemical inhibitors using cDNA-expressed cytochromes P450

Cited by 123 publications

References 23 publications

Prediction of the Intestinal First-Pass Metabolism of CYP3A Substrates in Humans Using Cynomolgus Monkeys

Prediction of the Intestinal First-Pass Metabolism of CYP3A Substrates in Humans Using Cynomolgus Monkeys

Metabolism of 18-Methoxycoronaridine, an Ibogaine Analog, to 18-Hydroxycoronaridine by Genetically Variable CYP2C19

Interindividual Variability in 2-Hydroxylation, 3-Sulfation, and 3-Glucuronidation of Ethynylestradiol in Human Liver

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