The present disclosure provides compounds of any one of Formulae (I), (II), and (III). The compounds described herein are inhibitors of histone methyltransferases (e.g., enhancer of zeste homolog 1 (EZH1) and enhancer of zeste homolog 2 (EZH2)) and are useful in treating and/or preventing a broad range of diseases (e.g., proliferative diseases). Also provided in the present disclosure are pharmaceutical compositions, kits, methods, and uses including or using a compound described herein.