Inclusion Criteria

• Men or women
• ≥ 65 years of age 
• > 18 and < 65 years of age, provided that they meet at least one of the following
  • Creatinine clearance 30 to 69 mL/min
  • A score higher than 6 on the Cumulative Illness Rating Scale-Geriatric
• ECOG performance status of 0, 1, or 2.
• Diagnosis of CD20+ CLL
• Active disease meeting ≥ 1 of IWCLL 2008 criteria for requiring treatment
• Meet the following laboratory parameters
  • ANC ≥ 750 cells/μL, or ≥ 500 cells/μL with documented bone marrow involvement, and independent of growth factor support 7 days before assessment
  • Platelet count ≥ 50,000 cells/μL, or ≥ 30,000 cells/μL with documented bone marrow involvement, and without transfusion support 7 days before assessment
    • Transfusion-dependent thrombocytopenia is excluded
  • Serum AST and ALT/SGPT ≤ 3.0 x ULN
  • Total bilirubin ≤ 1.5 x ULN
  • Estimated creatinine clearance ≥ 30 mL/min

Exclusion Criteria

• Any prior systemic treatment for CL.
• Known CNS lymphoma or leukemia
• Known prolymphocytic leukemia
• History of, or currently suspected, Richter's syndrome
• Uncontrolled autoimmune hemolytic anemia or idiopathic thrombocytopenia purpura
• Major surgery within 4 weeks before first dose of study drug
• Prior malignancy, except for adequately treated lentigo maligna melanoma, non-melanomatous skin cancer, in situ cervical carcinoma, or other malignancy treated with no evidence of active disease > 3 years before screening and at low risk for recurrence
• Significant cardiovascular disease within 6 months of screening
• Known history of infection with HIV
• History of stroke or intracranial hemorrhage within 6 months before randomization
• Known history of a bleeding diathesis
• Requires or receiving anticoagulation with warfarin or equivalent vitamin K antagonists within 7 days of first dose of study drug