An orally bioavailable, selective inhibitor of EZH2 (Ki = 2.5 nM); blocks H3K27 trimethylation in both wild-type and mutant lymphoma cells (IC50s range from 2-90 nM); induces apoptosis and differentiation specifically in SMARCB1-deleted malignant rhabdoid tumor cells and promotes their regression in xenograft-bearing mice