Oral Clofarabine in Chronic Lymphocytic Leukemia (CLL)

Inclusion Criteria:

* Patients with chronic lymphocytic leukemia (CLL), CLL/PLL (as defined by FAB \[French-American-British Classification\]), small lymphocytic lymphoma (SLL) and prolymphocytic leukemia (PLL) who have relapsed from or are refractory to at least one fludarabine-based regimen and no greater than 2 regimens.
* Absolute neutrophil count (ANC) \>= 1 x 109/L and platelet count \>= 50 x 109/L.
* Adequate organ function as indicated by the following laboratory values: serum creatinine \</= 1 mg/dL; if serum creatinine \> 1 mg/dL, then the estimated glomerular filtration rate (GFR) must be \> 60 ml/min/1.73 m2 as calculated by the Modification of Diet in Renal Disease equation; serum bilirubin \</= 1.5 mg/dL x ULN; aspartate transaminase (AST)or alanine transaminase (ALT) \</= 2.5 x ULN; alkaline phosphatase \</= 2.5 x ULN.
* ECOG performance status \<= 2.
* Age \>/= 18 years.

Exclusion Criteria:

* Patients with NYHA \>/= grade 3 heart disease as assessed by history and/or physical examination.
* Pregnant or breastfeeding women or patients who are unwilling or unable to practice adequate contraception. Positive pregnancy test for women of child bearing potential (defined as not post-menopausal for 12 months or no previous surgical sterilization).
* Chemotherapy within 4 weeks of starting therapy, or concurrent anticancer therapy (chemotherapy, radiotherapy, or biologic therapy).
* Other malignancy within 3 years except in situ carcinoma.
* Unwilling or unable to provide informed consent.
* Known hypersensitivity to nucleoside analogues.
* Any other significant medical condition that compromises safety, compliance or study conduct, including but not limited to uncontrolled hypertension, unstable angina, myocardial infarction within 6 months, ventricular arrhythmia, active infection, and known hepatitis.