Abstract
The complexity of in vitro kinetic phenomena observed for CYP3A4 substrates (homo- or heterotropic cooperativity) confounds the prediction of drug-drug interactions, and an evaluation of alternative and/or pragmatic approaches and substrates is needed. The current study focused on the utility of the three most commonly used CYP3A4 in vitro probes for the prediction of 26 reported in vivo interactions with azole inhibitors (increase in area under the curve ranged from 1.2 to 24, 50% in the range of potent inhibition). In addition to midazolam, testosterone, and nifedipine, quinidine was explored as a more “pragmatic” substrate due to its kinetic properties and specificity toward CYP3A4 in comparison with CYP3A5. Ki estimates obtained in human liver microsomes under standardized in vitro conditions for each of the four probes were used to determine the validity of substrate substitution in CYP3A4 drug-drug interaction prediction. Detailed inhibitor-related (microsomal binding, depletion over incubation time) and substrate-related factors (cooperativity, contribution of other metabolic pathways, or renal excretion) were incorporated in the assessment of the interaction potential. All four CYP3A4 probes predicted 69 to 81% of the interactions with azoles within 2-fold of the mean in vivo value. Comparison of simple and multisite mechanistic models and interaction prediction accuracy for each of the in vitro probes indicated that midazolam and quinidine in vitro data provided the best assessment of a potential interaction, with the lowest bias and the highest precision of the prediction. Further investigations with a wider range of inhibitors are required to substantiate these findings.
Footnotes
-
Financial support for this project was provided by the following Centre for Applied Pharmacokinetic Research Consortium members: Bristol Myers-Squibb Co., Eli Lilly & Co., GlaxoSmithKline, Novartis, Pfizer Central Research, F. Hoffmann-La Roche, and Servier.
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
doi:10.1124/jpet.104.082826.
-
ABBREVIATIONS: DDI, drug-drug interaction(s); AUC, area under the curve; AUCi, area under the curve in the presence of the inhibitor; P450, cytochrome P450; LC, liquid chromatography; MS, mass spectometry; MS/MS, tandem mass spectrometry; S, substrate; I, inhibitor; SEI, ISE, SES, SESI, inhibitor and substrate or two-substrate bound complexes with an enzyme.
- Received December 23, 2004.
- Accepted March 18, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|