TY - JOUR T1 - Expression of the Human <em>CYP3A4</em> Gene in the Small Intestine of Transgenic Mice: In Vitro Metabolism and Pharmacokinetics of Midazolam JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 548 LP - 558 DO - 10.1124/dmd.31.5.548 VL - 31 IS - 5 AU - Camille P. Granvil AU - Ai-Ming Yu AU - Guillermo Elizondo AU - Taro E. Akiyama AU - Connie Cheung AU - Lionel Feigenbaum AU - Kristopher W. Krausz AU - Frank J. Gonzalez Y1 - 2003/05/01 UR - http://dmd.aspetjournals.org/content/31/5/548.abstract N2 - Human cytochrome P450 3A4 (CYP3A4) is the most abundant hepatic and intestinal phase I drug-metabolizing enzyme, and participates in the oxidative metabolism of approximately 50% of drugs on the market. In the present study, a transgenic-CYP3A4(Tg-CYP3A4) mouse model that expresses CYP3A4 in the intestine and is phenotypically normal was generated, which was genotyped by both polymerase chain reaction and Southern blotting. Intestinal microsomes prepared from Tg-CYP3A4 mice metabolized midazolam (MDZ) to 1′-hydroxymidazolam about 2 times, and to 4-hydroxymidazolam around 3 times faster than that from wild-type (WT) mice. These increased MDZ hydroxylation activities were completely inhibited by an anti-CYP3A4 monoclonal antibody. The time course of plasma MDZ and its metabolite concentrations was measured after intravenous (0.25 mg/kg) and oral (2.5 mg/kg) administration of MDZ, and pharmacokinetic parameters were estimated by fitting to a noncompartmental model. Pretreatment with ketoconazole increased orally dosed MDZ maximum plasma concentration (Cmax), time of the maximum concentration, area under the plasma concentration-time curve from zero to infinity (AUC0-∞), and elimination half-life (t1/2) to 3.2-, 1.7-, 7.7-, 2-fold, and decreased MDZ apparent oral clearance about 8-fold in Tg-CYP3A4 mice. The ratios of MDZCmax, AUC0-∞,t1/2 and bioavailability between Tg-CYP3A4 and WT mice after the oral dose of MDZ were 0.3, 0.6, 0.5, and 0.5, respectively. These results suggest that this Tg-CYP3A4 mouse would be an appropriate in vivo animal model for the evaluation of human intestine CYP3A4 metabolism of drug candidates and potential food-drug and drug-drug interactions in preclinical drug development. U.S. Government ER -