UNC0638 is a potent, selective and cell-penetrant chemical probe for G9a and GLP with IC50 of <15 nM and 19 nM, respectively, shows selectivity over a wide range of epigenetic and non-epigenetic targets.

The methylation of lysine residues on histones plays a central role in determining euchromatin structure and gene expression. The histone methyltransferase (HMTase) G9a can mono- or dimethylate lysine 9 on histone 3 (H3), contributing to early embryogenesis, genomic imprinting, and lymphocyte development.UNC0638 is a potent G9a HMTase inhibitor, exhibiting an IC50 value of <15 nM in vitro. UNC0638 also inhibits GLP, a closely-related H3K9 HMTase, with an IC50 value of 19 nM, but is more than 10,000-fold selective against SET7/9 (a H3K4 HMTase), SET8 (a H4K20 HMTase), PRMT3, and SUV39H2. UNC0638 inhibits H3K9 dimethylation in MDA-MB231 cells with an IC50 value of 81 nM and demonstrates favorable separation of functional and toxic effects.