Phase II Trial of Decitabine in Patients With Chronic Myelogenous Leukemia Accelerated Phase Who Are Refractory to Imatinib Mesylate (Gleevec)

Inclusion: * Histologically confirmed diagnosis of CML accelerated phase * Ph chromosome-positive * Previous treatment with imatinib mesylate resulting in: i) Hematologic Resistance / Hematologic Refractory: Based on a physician's (documented) decision to discontinue imatinib mesylate treatment due to failure of continued benefit or no benefit to the patient, ii) Imatinib Mesylate Intolerance: any toxicity resulting in a physician's (documented) decision to discontinue imatinib mesylate treatment. * Patients must have recovered from the side effects of previous CML therapy for accelerated phase with the exception of hydroxyurea * Age \>/= 2 years * Bilirubin \</= 3 x the upper limit of normal (ULN), SGOT and SGPT \</= 3 x ULN, except \</= 5 x ULN in leukemic involvement of the liver, serum creatinine \</= 2 x ULN * WHO performance status 0-3 * A negative serum hCG pregnancy test in patients of childbearing potential * Able to give signed informed consent directly or through a parent or guardian for minors Exclusion: * Leukemic involvement of the central nervous system * Active malignancy other than CML or non-melanoma cancer of the skin * Previous treatment for CML with another investigational agent within 28 days of study entry * At study entry, patients who were treated with: imatinib mesylate within the past 48 hours; interferon-alpha within the past 48 hours; homoharringtonine within the past 14 days; low-dose cytosine arabinoside within 7 days, moderate dose within 14 days, or high dose within 28 days; etoposide, anthracyclines, or mitoxantrone within 21 days; busulfan within the past six weeks * Patients who had received hematopoietic stem cell transplantation within 6 weeks of Day 1 decitabine therapy * Patients with Grade 3/4 cardiac disease or any other serious concurrent medical condition. * Patients who are pregnant or nursing. All patients of childbearing potential must practice effective methods of contraception while on study. * Patients with mental illness or other condition precluding their ability to give informed consent or to comply with study requirements * Patients with systemic, uncontrolled infections