Defining the Selectivity of Chemical Inhibitors Used for Cytochrome P450 Reaction Phenotyping: Overcoming Selectivity Limitations with a Six-Parameter Inhibition Curve-Fitting Approach

• DOI: 10.1124/dmd.122.000884
• Publication Date: 2022-07-01T14:30:14Z
• Authors: Angela C. Doran; Woodrow Burchett; Connor Landers; Gabrielle M. Gual...; Amanda Balesano; Heather Eng; Alyssa L Dantonio; Theunis C. Goosen; R. Scott Obach
• Keywords: Quinidine

The utility of chemical inhibitors in cytochrome P450 (CYP) reaction phenotyping is highly dependent on their selectivity and potency for target CYP isoforms. In the present study, 17 CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 3A4/5 commonly used were evaluated cross-enzyme pooled human liver microsomes. data using a statistical desirability analysis to identify (1) superior (2) optimal concentrations each. Among evaluated, <i>α</i>-naphthoflavone, furafylline, sulfaphenazole, tienilic acid, <i>N</i>-benzylnirvanol, quinidine most selective, such that respective enzymes inhibited by ∼95% without inhibiting any other enzyme more than 10%. Other employed inhibitors, as ketoconazole montelukast, among others, insufficient yield concentration could adequately inhibit affecting enzymes. To overcome these shortcomings, an experimental design was developed wherein dose response from densely sampled multi-concentration inhibition curve are analyzed six-parameter function, allowing accounting off-target isoforms reliable determination maximum targeted inhibition. approach exemplified rosiglitazone <i>N</i>-demethylation, catalyzed both CYP2C8 3A4, able discern montelukast enzyme. This methodology yields accurate estimates contributions phenotyping. <h3>SIGNIFICANCE STATEMENT</h3> Isoform-selective important tools identifying quantifying part assessment projecting drug-drug interactions. However, currently practices fail compensate shortcomings inhibitor resulting confounding impact contribution drug clearance. this report, we describe detailed half maximal inhibitory (IC₅₀) study with 6-parameter modeling contribution.