Forodesine Hydrochloride (BCX-1777) for B-Cell Acute Lymphoblastic Leukemia

Inclusion Criteria: * Documented B-cell acute lymphoblastic leukemia (B-ALL), which under WHO Guidelines is now referred to as precursor B-lymphoblastic leukemia/lymphoma * Must have failed at least 1 treatment regimen for B-ALL, which under WHO Guidelines is now referred to as precursor B-lymphoblastic leukemia/lymphoma * Performance status of ≤2 by Eastern Cooperative Oncology Group (ECOG) criteria * Any age is allowed * Life expectancy of at least 3 months * Adequate liver function (aspartate transaminase \[AST\] and/or alanine transaminase \[ALT\] not \>3 times upper limits of normal \[ULN\]) * Adequate kidney function (calculated creatinine clearance \>40 mL/min) * Negative serum or urine pregnancy test within 2 to 7 days prior to the start of study treatment 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 in such a manner that the risk of pregnancy is minimized. Acceptable contraceptives include intra-uterine devices (IUDs), hormonal contraceptives (oral, depot, patch, or injectable) and double barrier methods such as condoms or diaphragms with spermicidal gel or foam. * Signed informed consent form (ICF), minor assent form (if applicable), prior to start of any study-specific procedures Exclusion Criteria: * Active serious infection not controlled by oral or intravenous antibiotics * Treatment with any investigational antileukemic agent or chemotherapy agent in the last 7 days prior to study entry and lack of full recovery from side effects due to prior therapy independent of when that therapy was given * Rapidly progressive disease with compromised organ function judged to be life-threatening by the Investigator * Patients with clinical evidence of active central nervous system (CNS) disease * Concurrent treatment with other anticancer agents * Pregnant and/or lactating female * Patients with known human immunodeficiency virus (HIV) infection HIV testing will be performed at the Screening visit for patients who have not been tested within 6 months of receiving study drug, as well as those patients who have had exposure or have been transfused with blood products that were not appropriately screened. * Patients with known active hepatitis B and/or hepatitis C infection Hepatitis testing will be performed at the Screening visit for patients who have not been tested within 6 months of receiving study drug, as well as those patients who have had exposure or have been transfused with blood products that were not appropriately screened. * Hypersensitive or intolerant to any component of the study drug formulation