1. Patients with a diagnosis of CLL/SLL who are refractory to and/or relapsed after at least one prior therapy will be eligible (Cohort 1). Untreated patients with high-risk features (del(17p), or mutated TP53, or del(11q), or unmutated IGHV, or >/= 65 years of age) are eligible (Cohort 2) provided they have active disease requiring treatment as defined by the International Working Group for CLL (IWCLL)