Short Communication The Combination of Chemical and Antibody Inhibitors for Superior P450 3A Inhibition in Reaction Phenotyping Studies

Cytochrome P450 (P450) reaction phenotyping is a key process toward accurately determining the contribution of different P450s to the metabolism of new chemical entities. The significance of P450s to drug disposition has led to the identification of selective chemical and antibody inhibitors for individual P450 enzymes. De-spite these advances, the maximal inhibition attainable is limited by the use of inhibitor concentrations that maintain selectivity for the individual P450s. Thus, most commercially available inhibitors produce a maximal inhibition of 80%. Herein, the combination of chemical plus antibody inhibitors is explored to find whether P450 3A could be selectively and completely (>99%) inhibited by using both inhibitors simultaneously. The majority of marketed drugs are metabolized by members of the cytochrome P450 (P450) superfamily of enzymes (Wienkers and Heath, 2005). Given the limited number of P450 enzymes that con