EPZ5676 is primarily used in research settings as a potent and selective inhibitor of the DOT1L histone methyltransferase. This enzyme plays a critical role in the methylation of histone H3, which is associated with the regulation of gene expression. By inhibiting DOT1L, EPZ5676 is studied for its potential to disrupt abnormal gene expression patterns in certain cancers, particularly those involving MLL (mixed-lineage leukemia) gene rearrangements. Its application is largely focused on understanding the mechanisms of epigenetic regulation and exploring therapeutic strategies for leukemia and other malignancies driven by epigenetic dysregulation. Researchers use it to investigate the effects of DOT1L inhibition on cancer cell proliferation, differentiation, and apoptosis, providing insights into novel treatment approaches.