Abstract
Current molecular tools lack the ability to differentiate the activity of CYP3A4 and CYP3A5 in biological samples such as human liver microsomes. Kinetic experiments and the CYP3A4 crystal structure indicate that the active sites of both enzymes are large and flexible, and have more than one binding subsite within the active site. 1-(4-Imidazopyridinyl-7phenyl)-3-(4′-cyanobiphenyl) urea (SR-9186) was optimized through several rounds of structural refinement from an initial screening hit to obtain greater than 1000-fold selectivity for the inhibition of CYP3A4 versus CYP3A5. Characterization data demonstrate selectivity using midazolam and testosterone hydroxylation assays with recombinant cytochrome P450, pooled human liver microsomes, and individually genotyped microsomes. Clear differences are seen between individuals with CYP3A5*1 and *3 genotypes. The antifungal drug ketoconazole is the most commonly used CYP3A inhibitor for in vitro and in vivo studies. A direct comparison of SR-9186 and ketoconazole under typical assay conditions used in reaction phenotyping studies demonstrated that SR-9186 had selectivity over CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A5 greater than or equal to that of ketoconazole. In addition, the long half-life (106 min) of SR-9186 in incubations containing 1 mg/ml human liver microsomes provided sustained CYP3A4 inhibition.
Footnotes
This work was supported by the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant 1R21-DK091630]; and the Pharmacokinetics Dynamics and Metabolism group of Pfizer Inc. (Fellowship to X.L.).
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
ABBREVIATIONS:
- P450
- cytochrome P450
- LC
- liquid chromatography
- HPLC
- high-performance liquid chromatography
- HLM
- human liver microsomes
- MS/MS
- tandem mass spectrometry
- SR-9186
- 1-(4-imidazopyridinyl-7phenyl)-3-(4′-cyanobiphenyl) urea.
- Received April 9, 2012.
- Accepted June 13, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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