Validation of Human Sterol 14α-Demethylase (CYP51) Druggability: Structure-Guided Design, Synthesis, and Evaluation of Stoichiometric, Functionally Irreversible Inhibitors

Sterol 14α-demethylases (CYP51)
are the cytochrome P450 enzymes
required for biosynthesis of sterols in eukaryotes, the major targets
for antifungal agents and prospective targets for treatment of protozoan
infections. Human CYP51 could be and, for a while, was considered
as a potential target for cholesterol-lowering drugs (the role that
is now played by statins, which are also in clinical trials for cancer)
but revealed high intrinsic resistance to inhibition. While microbial
CYP51 enzymes are often inhibited stoichiometrically and functionally
irreversibly, no strong inhibitors have been identified for human
CYP51. In this study, we used comparative structure/functional analysis
of CYP51 orthologs from different biological kingdoms and employed
site-directed mutagenesis to elucidate the molecular basis for the
resistance of the human enzyme to inhibition and also designed, synthesized,
and characterized new compounds. Two of them inhibit human CYP51 functionally
irreversibly with their potency approaching the potencies of azole
drugs currently used to inhibit microbial CYP51.