TY - JOUR T1 - The Development of a Cocktail CYP2B6, CYP2C8, and CYP3A5 Inhibition Assay and a Preliminary Assessment of Utility in a Drug Discovery Setting JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 381 LP - 385 DO - 10.1124/dmd.106.012344 VL - 35 IS - 3 AU - Charles J. O'Donnell AU - Ken Grime AU - Paul Courtney AU - Dean Slee AU - Robert J. Riley Y1 - 2007/03/01 UR - http://dmd.aspetjournals.org/content/35/3/381.abstract N2 - Tools for studying the roles of CYP2B6, CYP2C8, and CYP3A5 in drug metabolism have recently become available. The level of interest in these enzymes has been elevated because investigations have revealed substrate promiscuity and/or polymorphic expression. In this study, we aimed to develop a single cocktail inhibition assay for the three enzymes and assess its utility in drug discovery. Bupropion hydroxylation, amodiaquine N-deethylation, and midazolam 1′-hydroxylation were chosen as probe reactions for CYP2B6, CYP2C8, and CYP3A5 and were analyzed using liquid chromatography-tandem mass spectrometry. Kinetic analyses were performed to establish suitable conditions for inhibition assays, which were subsequently automated. CYP2B6, CYP2C8, and CYP3A5 IC50 values were determined for marketed drugs and almost 200 AstraZeneca discovery compounds from 16 separate discovery projects. For the marketed drugs, results obtained were comparable with literature values. Data were also compared with IC50 values determined for CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. In this dataset, the majority of compounds were more potent inhibitors of CYP2C9, CYP2C19, CYP2D6, and CYP3A4 than of CYP2B6, CYP2C8, or CYP3A5. The potential impact of these findings on a cytochrome P450 inhibition strategy is discussed. The American Society for Pharmacology and Experimental Therapeutics ER -