Marked species differences in the bioavailability of midazolam in cynomolgus monkeys and humans

ABSTRACT:Induction of the cytochrome P450 (P450) enzyme is a major concern in the drug discovery processes. To predict the clinical significance of enzyme induction, it is helpful to investigate pharmacokinetic alterations of a coadministered drug in a suitable animal model. In this study, we focus on the induction of CYP3A, which is involved in the metabolism of approximately 50% of marketed drugs and is inducible in both the liver and intestine. As a marker substrate for CYP3A activity, alprazolam (APZ) was selected and characterized using recombinant CYP3A enzymes expressed in Escherichia coli. Both human CYP3A4 and its cynomolgus P450 ortholog predominantly catalyzed APZ 4-hydroxylation with sigmoidal kinetics. When administered intravenously and orally to cynomolgus monkeys, APZ had moderate clearance; its first-pass extraction ratio after oral dosing was estimated to be 0.09 in the liver and 0.45 in the intestine. Pretreatment with multiple doses of rifampicin (20 mg/kg p.o. for 5 days), a known CYP3A inducer, significantly decreased plasma concentrations of APZ after intravenous and oral administrations (0.5 mg/kg), and first-pass extraction ratios were increased to 0.39 in the liver and 0.63 in the intestine. The results were comparable to those obtained in clinical drug-drug interaction (DDI) reports related to CYP3A induction, although the rate of recovery of CYP3A activity seemed to be slower than rates estimated in clinical studies. In conclusion, pharmacokinetic studies using APZ as a probe in monkeys may provide useful information regarding the prediction of clinical DDIs due to CYP3A induction.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Alprazolam as an In Vivo Probe for Studying Induction of CYP3A in Cynomolgus Monkeys

Ohtsuka¹,

Yoshikawa²,

Kozakai³

et al. 2010

“…Indeed, it has been reported that human pharmacokinetics after intravenous administration of an investigational drug can be predicted more accurately from results obtained in monkeys than from those in rats and dogs (Ward and Smith, 2004). However, the oral bioavailability of some drugs, especially cytochrome P450 (P450) 3A4 substrates, is markedly lower in monkeys than humans (Takahashi et al, 2009), and it is often speculated that the cause is extensive first-pass metabolism in the monkey intestine (Sakuda et al, 2006;Nishimura et al, 2007;Ogasawara et al, 2007). Therefore, we anticipated that the prediction of intestinal first-pass metabolism in humans by in vivo methods using monkeys would be improved by taking the species differences in intrinsic intestinal metabolic activities between monkeys and humans into account.…”

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

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.

“…Unlike humans, cynomolgus monkeys show minimal bioavailability of midazolam (approximately 2-6%), even though F h was not small (ϳ66%) (Kanazu et al, 2004;Sakuda et al, 2006). Interestingly, Sakuda et al (2006) recently showed that midazolam is completely absorbed by intestinal tissue in cynomolgus monkey, implying that intestinal metabolism may have a crucial role in the low bioavailability of midazolam (Sakuda et al, 2006).…”

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confidence: 99%

“…Midazolam, a short-acting benzodiazepine central nervous system depressant, is a typical substrate of CYP3A, its oral bioavailability being 24 to 46% in humans (Sakuda et al, 2006). In humans, F a ⅐ F g and F h were estimated to be 57 and 56%, respectively , indicating that bioavailability of midazolam is affected by both intestinal and hepatic first-pass effects.…”

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confidence: 99%

Asymmetric Intestinal First-Pass Metabolism Causes Minimal Oral Bioavailability of Midazolam in Cynomolgus Monkey

Nishimura¹,

Amano²,

Kubo³

et al. 2007

ABSTRACT:Oral bioavailability of some drugs is substantially lower in cynomolgus monkeys than in various other species, including humans. In the present study, midazolam was used as a model drug to investigate the reason for the lower bioavailability in these monkeys. The bioavailability of midazolam after oral administration was minimal in monkeys and rats, being only 2.1 and 1.1%, respectively. In monkeys, this low bioavailability could not be explained simply in terms of a hepatic first-pass effect. To examine the roles of intestinal metabolism and transport, we evaluated apical-tobasal and basal-to-apical transport of midazolam, and the formation of metabolites in small intestinal tissues using an Ussing-type chamber. The values of mucosal extraction ratio were estimated to be 0.97, 0.93, and 0.89 during apical-to-basal transport in the upper, middle, and lower small intestine of monkeys, respectively, whereas the corresponding values for rats were close to zero, indicating that extensive metabolism of midazolam occurs, particularly in the upper region of the small intestine in monkeys, but not rats. Interestingly, formation of the metabolites was much greater during transport in the apical-to-basal direction than in the basalto-apical direction, and this could be well explained by a mathematical model based on the assumption that extensive metabolism is associated with the uptake process of midazolam from the apical cell surface. Thus, we conclude that an asymmetric distribution of metabolic activity in the small intestine, leading to extensive metabolism during uptake from the apical cell surface, accounts for the minimal oral bioavailability of midazolam in cynomolgus monkeys.