Recent developments in targeted therapy for MLL-r leukemia have been mainly focused on inhibiting the interaction between MLL1 or the MLL1-fusion protein and collaborating binding partners such as the Disruptor of Telomeric Silencing 1-like (Dot1L) (EPZ4777/EPZ-5676) [52–56], the Multiple Endocrine Neoplasia (Menin) protein (MI-2/MI-3) [57–62] or the WD repeat-containing protein 5 (WDR5) [63–65]. The gene discussed is KMT2A; the disease is leukemia.