Interaction of new sulfaphenazole derivatives with human liver cytochrome P4502Cs: Structural determinants required for selective recognition by CYP2C9 and for inhibition of human CYP2Cs

A series of new derivatives of sulfaphenazole (SPA), in which the NH, and p henyl substituents of SPA are replaced by various groups or in which the su lfonamide function of SPA is N-alkylated, were synthesized in order to furt her explore CYP 2C9 active site and to determine the structural factors exp laining the selectivity of SPA for CYP 2C9 within the human P450 2C subfami ly. Compounds in which the NH2 group of SPA was replaced with R-1 = CH3, Br , CH = CH2, CH2CH = CH2, and CH2CH2OH exhibited a high affinity for CYP 2C9 , as shown by the dissociation constant of their CYP 2C9 complexes, K-s, wh ich was determined by difference visible spectroscopy (K-s between 0.1 and 0.4 muM) and their constant of CYP 2C9 inhibition (K-i between 0.3 and 0.6 muM). This indicates that the CYP 2C9-iron(III)-NH2R bond previously descri bed to exist in the CYP 2C9-SPA complex does not play a key role in the hig h affinity of SPA for CYP 2C9. Compounds in which the phenyl group of SPA w as replaced with various aryl or alkyl R-2 substituents only exhibited a hi gh affinity for CYP 2C9 if R-2 is a freely rotating and sufficiently electr on-rich aryl substituent. Finally, compounds resulting from a N-alkylation of the SPA. sulfonamide function (R-3 = CH3, C2H5, or C3H7) did not retain the selective inhibitory properties of SPA toward CYP 2C9. However, they ar e reasonably good inhibitors of CYP 2C8 and CYP 2C18 (IC50 similar to 20 mu M). These data allow one to better understand the structural factors that a re important for selective binding in the CYP 2C9 active site. They also pr ovide us with clues towards new selective inhibitors of CYP 2C8 and CYP 2C1 8. (C) 2001 Academic Press.