A Study to Customize Ibrutinib Treatment Regimens for Participants With Previously Untreated Chronic Lymphocytic Leukemia

Inclusion Criteria:

• Diagnosis of chronic lymphocytic leukemia/ small lymphocytic lymphoma (CLL/SLL) asper International Workshop on Chronic Lymphocytic Leukemia (iwCLL) 2018 diagnosticcriteria

• For ibruinib + venetocIax (I+V) cohorts: eastern cooperative oncology group (ECOG)performance status of 0-1. For ibrutinib monotherapy cohorts: ECOG performancestatus of 0-2

• Measurable nodal disease by computed tomography (CT), defined as at least 1 lymphnode greater than and equal to (>=) 1.5 centimeters (cm) in longest diameter

• A participant using oral contraceptives must use an additional contraceptive method

• A participant must agree not to be pregnant, breastfeeding, or planning to becomepregnant while enrolled in this study or until 1 month after last dose or per locallabel if more conservative (for example, 3 months in European Union or Canada and 1month in United States)

Exclusion Criteria:

• Uncontrolled autoimmune hemolytic anemia or idiopathic thrombocytopenia purpura,such as those participants with a declining hemoglobin level or platelet countsecondary to autoimmune destruction within the 4 weeks prior to first dose of studytreatment, or the need for prednisone greater than (>) 20 milligrams (mg) daily (orcorticosteroid equivalent) to treat or control the autoimmune disease

• Known bleeding disorders (example, von Willebrand's disease or hemophilia)

• Stroke or intracranial hemorrhage within 6 months prior to enrollment

• Known or suspected Richter's transformation or central nervous system (CNS)involvement

• Currently active, clinically significant cardiovascular disease, such asuncontrolled arrhythmia or Class II, III, or IV congestive heart failure as definedby the New York Heart Association Functional Classification