Inclusion Criteria:

   - Documented T-cell leukemia (precursor T-lymphoblastic leukemia/lymphomia or T-PLL)

   - Failure to have responded to one or more standard regimens for their disease.

   - Performance status of <=2 by Eastern Cooperative Oncology Group (ECOG) criteria

   - All ages are eligible

   - Life expectancy of at least 3 months

   - Adequate liver function (aspartate transaminase [AST] and/or alanine transaminase
   [ALT] not >3 times upper limits or normal [ULN])

   - Adequate kidney function (calculated creatinine clearance >50 mL/min)

   - Negative urine pregnancy test within 2 to 7 days prior to the start of study
   treamtment in females of childbearing potential

   - Females of childbearing potential and males must be willing and able to use an
   adequate method of contraception to avoid pregnancy for the duration of the study

   - Signed informed consent/assent form (ICF) prior to start of any study specific
   procedures

Exclusion Criteria:

   - Patients with known HIV infection or human T-cell leukemia virus type (HTLV-1)

   - Patients with known Hepatitis B and/or Hepatitis C active infection

   - Patients with active CMV infection

   - Tumor-related central nervous system (CNS) leukemia requiring active treatment

   - Active serious infection not controlled by oral or IV antibiotics

   - Treatment with any investigational anti-leukemic agent or chemotherapy agent within 7
   days prior to study entry, unless full recovery from side effects has occurred.

   - Rapidly progressive disease with compromised organ function judged to be
   life-threatening by the investigator

   - Concurrent treatment with other anticancer agents (corticosteroid use will not be
   excluded, but patient must remain on the stable dose)

   - Cutaneous T-cell lymphoma (CTCL) diagnosis (including Sezary Syndrome)

   - Pregnant and/or lactating women