1. CIRS ≥ 6; 2. Creatinine Clearance < 70 mL/min; 3. Subject is not a candidate for a chemoimmunotherapy in the opinion of investigator. ii. Treatment with an approved BTK inhibitor is not required if subject has contraindications or is not a candidate for such a therapy in the opinion of the investigator. b. For Arm B, subjects with treatment-naïve or R/R CLL must meet the following criteria: i. Dose Escalation Phase: Subjects must not have received prior treatment with ibrutinib (or any other approved BTK inhibitors) and must have either R/R CLL or treatment naïve (ie, first-line) CLL if the subject: