Currently, two DNMT inhibitors (DNMTi), the nucleoside analogues azacitydine (5-AZA) and decitabine (5-AZA-CdR), have been approved by FDA and the European Medicines Agency (EMA) against myelodysplastic syndromes (MDS), acute myeloid leukaemia (AML), and chronic myelomonocytic leukaemia (CMML). This evidence concerns the gene DNMT1 and chronic myelomonocytic leukemia.