A selective EZH2 inhibitor (IC50s = 0.24, 0.51, and 6.1 nM for wild-type EZH2, Y641N mutant EZH2, and wild-type EZH1, respectively); decreases cellular levels of H3K27me3, triggering cell cycle arrest and apoptosis in NHL cell lines (EC50 = 70 nM) and NHL xenografts (200 mg/kg/twice a day)