Repeat-Dose of Forodesine Hydrochloride (BCX-1777) Infusion in Patients With Advanced T-Cell Leukemia

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