KH-4-43 is a small moelcule E3 CRL4 inhibitor and exhibits antitumor potential, directly and selectively binds to the purified E3 ROC1-CUL4A CTD complex with Kd of 83 nM.KH-4-43 weakly binds to the purified, highly related E3 ROC1-CUL1 CTD complex with Kd of 9.4 uM, >100-fold less potent than ROC1-CUL4A CTD, showed little effect on Ub thiol ester formation with E1/E2 Cdc34.KH-4-43 inhibited the ubiquitination of CK1α by CRL4CRBN in vitro. Treatment of cells with KH-4-43 caused accumulation of the E3 CRL4 substrate CDT1.KH-4-43 inhibited cell viability against a panel of tumor lines, NB-4, MV4-11, OVCAR-3, and CAPAN-2 cell with IC50 of 1.8, 3.0, 3.9, and 4.8 uM, respectively.KH-4-43 suppress the growth of human tumor xenografts in mice.
