Currently, two DNMT inhibitors – azanucleosides – have been approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of certain forms of acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS): 5-aza-cytidine (AZA; Vidaza®, Celgene, New Jersey, USA) [27–29] and 5-aza-2’-deoxycytidine (DAC; Dacogen®, Astex, Cambridge, UK) [30, 31]. Here, DNMT1 is linked to acute myeloid leukemia.