Azacitidine for the treatment of myelodysplastic syndrome

The myelodysplastic syndromes (MDS) encompass a heterogeneous group of malignant hematologic disorders characterized by ineffective hematopoiesis, peripheral cytopenias, frequent karyotypic abnormalities and significant risk for transformation to acute myeloid leukemia (AML). The prognosis of patients with intermediate- or high-risk MDS is very poor. This is due to the fact that standard therapeutic options are largely palliative. Neither autologous stem cell transplantation (SCT) nor chemotherapeutic regimens have been shown to prolong survival in patients with MDS. Allogeneic SCT, while potentially curative, is only available to a selected group of patients and is associated with high morbidity and mortality in elderly patients, which constitute the majority of patients with MDS. Hypermethylation of tumor-suppressor genes has been invoked as an important pathogenetic mechanism in MDS. The pyrimidine nucleoside analog azacitidine, which inhibits DNA methyltransferases, has recently become the first therapeutic to prolong survival in patients with MDS, thus changing the natural history of these malignancies. The activity of azacitidine in MDS has spurred the development of combinations of this agent with other epigenetic modifiers for the treatment of MDS and AML.