Structure-Based Design and Characterization of the Highly Potent and Selective Covalent Inhibitors Targeting the Lysine Methyltransferases G9a/GLP

Protein
lysine methyltransferases G9a and GLP, which catalyze mono-
and di-methylation of histone H3K9 and nonhistone proteins, play important
roles in diverse cellular processes. Overexpression or dysregulation
of G9a and GLP has been identified in various types of cancer. Here,
we report the discovery of a highly potent and selective covalent
inhibitor 27 of G9a/GLP via the structure-based drug
design approach following structure–activity relationship exploration
and cellular potency optimization. Mass spectrometry assays and washout
experiments confirmed its covalent inhibition mechanism. Compound 27 displayed improved potency in inhibiting the proliferation
and colony formation of PANC-1 and MDA-MB-231 cell lines and exhibited
enhanced potency in reducing the levels of H3K9me2 in cells compared
to noncovalent inhibitor 26. In vivo, 27 showed significant antitumor efficacy in the PANC-1
xenograft model with good safety. These results clearly indicate that 27 is a highly potent and selective covalent inhibitor of
G9a/GLP.