Discovery of a Potent, Selective, and Cell-Active SPIN1 Inhibitor.

The methyl-lysine reader protein SPIN1 plays important roles in various human diseases. However, targeting methyl-lysine reader proteins has been challenging. Very few cellularly active SPIN1 inhibitors have been developed. We previously reported that our G9a/GLP inhibitor UNC0638 weakly inhibited SPIN1. Here, we present our comprehensive structure-activity relationship study that led to the discovery of compound , a dual SPIN1 and G9a/GLP inhibitor, and compound (MS8535), a SPIN1 selective inhibitor. We solved the cocrystal structure of SPIN1 in complex with , confirming that occupied one of the three Tudor domains. Importantly, displayed high selectivity for SPIN1 over 38 epigenetic targets, including G9a/GLP, and concentration dependently disrupted the interactions of SPIN1 and H3 in cells. Furthermore, was bioavailable in mice. We also developed (MS8535N), which was inactive against SPIN1, as a negative control of . Collectively, these compounds are useful chemical tools to study biological functions of SPIN1.