Currently, two DNMT inhibitors (DNMTi), the nucleoside analogues, 5-azacitydine (azacitidine) and 5-aza-2′-deoxycytidine (decitabine), have been approved by Food and Drug Administration (FDA) and the European Medicines Agency (EMA) against myelodysplastic syndromes (MDS), AML, and chronic myelomonocytic leukemia (CMML). This evidence concerns the gene DNMT1 and myelodysplastic syndrome.