A Study to Evaluate PT-523 in Patients With Refractory Leukemia

Inclusion Criteria: Relapsed/refractory leukemias including acute non-lymphocytic leukemia (AML), acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), and chronic myelogenous leukemia in blastic phase (CML-BP) for which no standard therapies are anticipated to result in a durable remission; or poor-risk myelodysplasia (MDS) patients to include refractory anemia with excess blasts (RAEB) or excess blasts in transformation (RAEBT) and chronic myelomonocytic leukemia (CMML) who are either relapsed/refractory or who refuse/are not eligible for frontline therapy. Only patients with refractory ALL or CML in lymphoid blastic phase are eligible for phase II. ECOG performance status 0 - 2. Adequate organ function and bone marrow reserve. At least 4 weeks must have elapsed from the time of major surgery. Use of appropriate contraceptive method. Signed patient informed consent. Exclusion Criteria: Known human immunodeficiency virus (HIV). Active heart disease including myocardial infarction within previous 3 months, symptomatic coronary artery disease, arrhythmias not controlled by medication, or uncontrolled congestive heart failure. Patients receiving any other standard or investigational treatment for their leukemia other than corticosteriods, hydroxyurea, and 6-mercaptopurine. Any medical condition which, in the opinion of the investigator, places the patient at an unacceptably high risk for toxicities.