Structure-Based Discovery of (E)- and (Z)-4-Oxobut-2-enoate Derivatives as Novel Covalent Pin1 Inhibitors with Antitumor Activity.

Peptidyl-prolyl cis-trans isomerase Pin1 is a promising anticancer target that is overexpressed in numerous cancers and associated with poor prognosis. Herein, two series of covalent Pin1 inhibitors featuring an (E)- or a (Z)-4-oxobut-2-enoate moiety as the electrophilic warhead were discovered, and their binding features were revealed by six cocrystal structures. The binding kinetic investigations revealed that both (E)- and (Z)-4-oxobut-2-enoate warheads exhibited an appropriate electrophilic activity (kinact = 0.006-3.60 min-1), conferring them as favorable covalent warheads for developing potent Pin1 inhibitors. The SAR investigations resulted in four (Z)-isomers (T29, T39-T41: enzymatic IC50 = 0.02-0.08 μM) with excellent enzymatic activity, while the (E)-isomer T7 (enzymatic IC50 = 1.54 μM) was found to potently suppress the proliferation of MDA-MB-468 cancer cells by downregulating the Pin1 substrates c-Myc and Cyclin D1. Altogether, 4-oxobut-2-enoate derivatives were disclosed as new templates for further developing potent covalent Pin1 inhibitors.