 This was a multicenter, Phase 1, standard 33 dose-escalation study to evaluate the safety and anti-neoplastic activity of CAT-8015 in relapsed or refractory participants with CLL, PLL, or SLL. Participants in the initial dose cohort were to receive CAT-8015 at a dose of 5 microgram per kilogram mcgkg CAT-8015, increasing to 10 mcgkg in the second dose cohort, and then increasing by 10 mcgkg increments in subsequent cohorts that is, to doses of 20, 30, 40, 50, 60 mcgkg, etc until a maximum tolerated dose MTD was identified. Following identification of the MTD, the MTD cohort was to be expanded to 16 participants. 