A Study to Evaluate the Efficacy of Venetoclax in Relapsed/Refractory Participants With Chronic Lymphocytic Leukemia (CLL) Including Those With 17p Deletion or TP53 Mutation or Those Who Have Received a Prior B-cell Receptor Inhibitor.

Inclusion Criteria:

- Participant has Eastern Cooperative Oncology Group (ECOG) performance score of less
than 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 IWCLL NCI-WG
Guidelines and:

- has an indication for treatment according to the 2008 Modified IWCLL NCI-WG
criteria

- has clinically measurable disease (lymphocytosis greater than 5 × 109/L and/or
palpable and measurable nodes by physical exam and/or organomegaly assessed by
physical exam)

- In addition, participants:

- with or without 17p deletion or TP53 mutation, assessed by a local laboratory in
bone marrow or peripheral blood AND/OR

- may have been previously treated with a prior B-cell receptor inhibitor

- Participant must have adequate bone marrow function, coagulation profile, renal, and
hepatic function, per laboratory reference range 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 first
dose 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 of
the skin

- previous malignancy confined and surgically resected (or treated with other
modalities) with curative intent

- Participant has active and uncontrolled autoimmune cytopenias (for 2 weeks prior to
Screening), including autoimmune hemolytic anemia and idiopathic thrombocytopenic
purpura despite low dose corticosteroids

- Participant has undergone an allogeneic stem cell transplant 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