Open-label Phase 3 BTK Inhibitor Ibrutinib vs Chlorambucil Patients 65 Years or Older With Treatment-naive CLL or SLL

Study design: This is a randomized, multicenter, open-label, Phase 3 study designed to compare the safety and efficacy of Ibrutinib versus Chlorambucil in treatment-naive patients 65 years or older who have CLL or SLL. Eligible patients will be randomized in a 1:1 ratio to Treatment Arm A or B: * Treatment Arm A: Oral Chlorambucil 0.5 mg/kg on Days 1 and 15 of each 28-day cycle; the dose can be increased, if well tolerated, in increments of 0.1 mg/kg on Day 1 of each cycle to a maximum of 0.8 mg/kg; patients receive a minimum of 3 and a maximum of 12 cycles, in the absence of progressive disease or unacceptable toxicity. * Treatment Arm B: Oral Ibrutinib 420 mg/day Randomization will be stratified on Eastern Cooperative Oncology Group (ECOG) performance status (0,1 versus 2); presence of advanced Rai stage (yes/no), advanced being defined as Stages 3-4; and geographic region: US versus non-US.