While a PRC2 inhibitor may be active in molecularly-defined subsets of SWI/SNF or KDM6A-mutant cancers, overall these data suggest this approach is unlikely to be broadly effective as a single agent in SWI/SNF or KDM6A-mutant cancers. In summary, MRTX2219 is a potent and orally bioactive EED inhibitor that represents a differentiated strategy to block PRC2 activity in selected cancers.