A Phase II Study of Intravenous Azacitidine Alone in Patients With Myelodysplastic Syndromes

Inclusion Criteria: 1. Pathological MDS either de novo or secondary, fitting any of the FAB classifications, confirmed by institutional pathologist within 2 weeks prior to start of treatment. Patients with 5% bone marrow blasts must also meet one of the following criteria: * Symptomatic anemia with either hemoglobin less than 10.0 g/dL or requiring RBC transfusion * Thrombocytopenia with a history of two or more platelet counts \< 50,000 / µL or a significant hemorrhage requiring platelet transfusions, or * Neutropenia with two or more absolute neutrophil counts less than 1,000 /µL. 2. ECOG performance status of 0-2. 3. Must give written informed consent indicating their awareness of the investigational nature of this study and its potential hazards. 4. Adequate renal and hepatic function (creatinine ≤ 150% of institutional upper limit of normal, total bilirubin ≤ 150% institutional upper limit of normal, AST ≤ 200% institutional upper limit of normal). 5. Life expectancy of at least 12 weeks. 6. Have not received any chemotherapy within 4 weeks of study enrollment and must have recovered from any treatment-related toxicities. 7. Women of childbearing age must have a negative serum pregnancy test prior to initiating therapy. 8. Sexually active women of childbearing potential must use effective birth control during the trial and for an appropriate period after the trial. 9. Men must be willing to avoid fathering a new child while receiving therapy with azacitidine. 10. ≥18 years, no upper age limit 11. Individuals who are candidates for hematopoietic stem cell transplantation and who meet all other study criteria may participate in the study and receive intravenous azacitidine alone as a treatment prior to transplantation. Exclusion Criteria: 1. Known CNS leukemia. 2. Previously received Azacitidine (Vidaza®, Pharmion Corp., Boulder CO) or decitabine (Dacogen®, MGI Pharma Inc. Bloomington, MN). 3. Known or suspected hypersensitivity to azacitidine or mannitol. 4. Receiving any other investigational agents within 30 days of first dose of study drug. 5. Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, congestive heart failure of NYHA class 3 or 4, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situation that would limit compliance with study requirements. 6. Known positive serology for HIV. 7. Had radiotherapy within 14 days prior to study enrollment. 8. Known presence of hepatic tumors. 9. \<18 years of age 10. Exclude women who are pregnant or breast feeding.