Inclusion Criteria:

          -  TdT-positive leukemia (ALL, AML, or blastic CML) that has failed at least one standard
             treatment regimen and for which no standard therapies are expected to result in
             durable remission. Leukemia is minimally defined as at least 20% blast cells present
             in marrow or peripheral blood. TdT must be expressed in at least 20% of blast cells
             present and documented either immunologically or biochemically;

          -  Age ≥18 years;

          -  Must understand and voluntarily sign informed consent;

          -  Adequate non-hematologic organ system function, defined by:

               -  Creatinine ≤1.5 times the upper limit of normal (ULN) and/or creatinine clearance
                  ≥60 mL/min

               -  AST and/or ALT ≤2.5 times upper limit of normal (ULN)

               -  Total bilirubin within institutional normal range

               -  Normal EKG and LVEF >40%, measured by EKG and MUGA scan, radionuclide
                  ventriculogram, or echocardiogram

          -  Life expectancy >3 months;

          -  Performance status (PS) >70% Karnofsky or ECOG ≤2;

          -  Women of childbearing potential must have a negative serum pregnancy test within 7
             days of starting study drug. A woman of child-bearing potential is a sexually mature
             woman who has not undergone a hysterectomy or who has not been naturally
             postmenopausal for at least 24 consecutive months (i.e., who has had menses at any
             time in the preceding 24 consecutive months);

          -  Male or female of child-bearing potential must agree to use adequate contraceptive
             methods

        Exclusion Criteria:

          -  Failure to meet inclusion criteria;

          -  Uncontrolled active infection;

          -  Extramedullary (CNS) disease;

          -  Serious concomitant medical illness, such as active infection, uncontrolled congestive
             heart failure, or uncontrolled diabetes or other metabolic disorder, or psychiatric
             illness;

          -  Pregnancy or lactation; females of child bearing potential must use adequate
             contraceptive methods;

          -  Less than 3 weeks since prior chemotherapy, radiation therapy, or immunotherapy.
             However, hydroxyurea is permitted up to 24 hours before the study is initiated;

          -  Less than 2 months following bone marrow or peripheral blood stem cell transplantation
             or treatment with donor lymphocyte infusion (DLI).