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).