In vitro activity: UNC0638 is a potent, selective and cell-penetrant chemical probe for G9a and GLP, with a toxicity/function ratio of>100, compared to<6 for BIX01294. UNC0638 is a selectivite inhibitor of G9a and GLP over a wide range of epigenetic and non-epigenetic targets. UNC0638 is more than 10,000-fold selective against SET7/9 (a H3K4 HMTase), SET8 (a H4K20 HMTase), PRMT3, and SUV39H2. In MDA-MB-231 cells, UNC0638 (48 h exposure) reduces H3K9me2 levels in a concentration-dependent manner with an IC50 of 81 nM. UNC0638 treatment of a variety of cell lines results in lower global H3K9me2 levels, equivalent to levels observed for small hairpin RNA knockdown of G9a and GLP with the functional potency of UNC0638 being well separated from its toxicity. UNC0638 markedly reduces the clonogenicity of MCF7 cells, reduces the abundance of H3K9me2 marks at promoters of known G9a-regulated endogenous genes and disproportionately affected several genomic loci encoding microRNAs. In mouse embryonic stem cells, UNC0638 reactivates G9a-silenced genes and a retroviral reporter gene in a concentration-dependent manner without promoting differentiation.

Kinase Assay: The enzymatic reactions are conducted in duplicate at room temperature for 1 hour in a 50 μL mixture containing PKMT assay buffer, substrate coated plate, 10 M SAM, a HMT enzyme (EZH2 (800 ng/reaction), MLL (300 ng/reaction), PRMT1 (0.5 ng/reaction), SUV39H1 (75 ng/reaction) and UNC0638 (0-1.25 μM). After enzymatic reactions, 100 μL of first antibody is added to each well and the plate is incubated at room temperature for an additional 1 h. 100 μL of secondary antibody is added to each well and the plate is incubated at room temperature for an additional 30 min. 100 μL of developer reagents are added to wells and luminescence is measured using a BioTek SynergyTM 2 microplate reader. Enzyme activity assays are performed in duplicates at each concentration. The luminescence data are analyzed using the computer software, Graphpad Prism.

Cell Assay: In MDA-MB-231 cells, in a concentration-dependent manner, exposure to UNC0638 for 48 h reduced H3K9me2 levels with an IC50 value of 81 ± 9 nM (n= 3), which showed considerably higher potency than BIX01294 (IC50= 500 ± 43 nM (n= 3)). In reducing H3K9me2 levels, UNC0638 was of greater maximum effect than BIX01294. This effect is close, but not equal, to the effect on the double knockdown of G9a and GLP via shRNA.