EI1 is a potent EZH2 inhibitor that has activity against both wild-type and Y641F mutant EZH2 (IC50s = 15 and 13 nM, respectively). It displays 90-fold selectivity for EZH2 over EZH1 and >10,000-fold selectivity over other lysine methyltransferases. EI1 blocks cellular H3K27 methylation and activates PRC2-specific gene expression. Inhibition of EZH2 by EI1 in diffused large B cell lymphoma cells carrying Y641 mutations results in decreased proliferation, cell cycle arrest, and apoptosis. MW: 390.5. Purity ≥98% by HPLC