Cytochrome P450 (CYP) enzymes are a superfamily of heme containing proteins that catalyze xenobiotic metabolism phase I reactions. Oxidation reactions are the most common CYP-catalyzed reactions for both endogenous substrates and exogenous compounds, including drugs, although CYP enzymes are capable also to catalyze reduction reactions. Whereas the majority of clinically used drugs are inactivated by CYPs, several prodrugs are bioconverted to their active species by these enzymes. Therefore, this mechanism could be exploited to a greater extend, e.g. by taking advantage of the different CYP enzymes to achieve targeted drug delivery, to improve efficacy or to decrease the unwanted adverse effects of existing and novel drug molecules. This review describes the potential of CYP enzymes in prodrug design and summarizes a wide variety of CYP-activated prodrug structures, which are on the market or under the development. The bioactivation mechanisms of each CYP-activated prodrug structure are described and the specificity for the different forms of CYP enzymes is discussed.

The purpose of this study was to determine the cytochrome P450 1A2 (CYP1A2) inhibition potencies of structurally diverse compounds to create a comprehensive three-dimensional quantitative structure-activity relationship (3D-QSAR) model of CYP1A2 inhibitors and to use this model to predict the inhibition potencies of an external set of compounds. Fifty-two compounds including naphthalene, lactone and quinoline derivatives were assayed in a 96-well plate format for CYP1A2 inhibition activity using 7-ethoxyresorufin O-dealkylation as the probe reaction. The IC50 values of the tested compounds varied from 2.3 microM to over 40,000 microM. On the basis of this data set, a comparative molecular field analysis (CoMFA) and GRID/GOLPE models were created that yielded novel structural information about the interaction between inhibitory molecules and the CYP1A2 active site. The created CoMFA model was able to accurately predict inhibitory potencies of several structurally unrelated compounds, including selective inhibitors of other cytochrome P450 forms.

Hydroxyimine derivatives of ketoprofen (1) and nabumetone (2) were synthesized and evaluated in vitro and in vivo as cytochrome P450-selective intermediate prodrug structures of ketones. 2 released nabumetone in vitro in the presence of isolated rat and human liver microsomes and in different recombinant human CYP isoforms. Bioconversion of 2 to both nabumetone and its active metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA), was further confirmed in rats in vivo. Results indicate that hydroxyimine is a useful intermediate prodrug structure for ketone drugs.

Since CYP enzymes reside predominantly in the liver and secondarily in the small intestine, the results indicate that cyclic phosphate prodrugs represent a very feasible liver- or intestinal-targeted drug delivery strategy for drug molecules containing an alcohol functionality. This may potentially improve the efficacy and the safety profile of the alcoholic parent drugs.