Tazemetostat trihydrochloride is a selective and orally available inhibitor of EZH2 (IC50: 4 nM for rat EZH2). It inhibits the activity of human PRC2-containing wild-type EZH2 (Ki: 2.5 nM). It inhibits EZH2 (IC50s: 11 and 16 nM in peptide assay and nucleo