A Study to Evaluate the Efficacy of Venetoclax Monotherapy in Relapsed/Refractory Participants With Chronic Lymphocytic Leukemia (CLL)

Inclusion Criteria:

• Participant has Eastern Cooperative Oncology Group (ECOG) performance score of lessthan or equal to 2
• Participant has relapsed/refractory disease (received at least 1 prior therapy)
• Participant has diagnosis of CLL that meets published 2008 Modified InternationalWorkshop for Chronic Lymphocytic Leukemia National Cancer Institute Working Group (IWCLL NCI-WG) Guidelines and:
• has an indication for treatment according to the 2008 Modified IWCLL NCI-WGcriteria
• has clinically measurable disease (lymphocytosis greater than 5 × 10^9/L and/orpalpable and measurable nodes by physical exam and/or organomegaly assessed byphysical exam)
• In addition, participants:
• with or without 17p deletion or TP53 mutation, assessed by a local laboratory inbone marrow or peripheral blood are eligible
• may have been previously treated with a prior B-cell receptor inhibitor
• Participant must have adequate bone marrow function, coagulation profile, renal, andhepatic function, per laboratory at Screening

Exclusion Criteria:

• Participant has developed Richter's transformation or Prolymphocytic leukemia
• Participant has previously received venetoclax
• History of active malignancies other than CLL within the past 2 years prior to firstdose of venetoclax, with the exception of:
• adequately treated in situ carcinoma of the cervix uteri
• adequately treated basal cell carcinoma or localized squamous cell carcinoma ofthe skin
• previous malignancy confined and surgically resected (or treated with othermodalities) with curative intent
• Participant has active and uncontrolled autoimmune cytopenias (for 2 weeks prior toScreening), including autoimmune hemolytic anemia and idiopathic thrombocytopenicpurpura despite low dose corticosteroids
• Participant has undergone an allogeneic stem cell transplant
• Treatment with any of the following within five half-lives or 14 days (if half-lifeunknown) as applicable prior to the first dose of venetoclax, or clinicallysignificant adverse effect(s)/toxicity(s) of the previous therapy have not resolved to < National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE)v4.03 Grade 2:
• Any anti-cancer therapy including chemotherapy, or radiotherapy;
• Investigational therapy, including targeted small molecule agents
• Participant is human immunodeficiency virus (HIV) positive
• Participant has known allergy to both xanthine oxidase inhibitors and rasburicase