A Study of Bruton's Tyrosine Kinase (BTK) Inhibitor Ibrutinib in Participants With Treatment-naive Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

Phase 1 Study of the Bruton's Tyrosine Kinase (BTK) Inhibitor Ibrutinib in Subjects With Treatment-naive Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

The purpose of this study is to evaluate the safety of Ibrutinib in Japanese participants with treatment-naive chronic lymphocytic leukemia ( CLL) or small lymphocytic lymphoma (SLL).

This is a Phase 1, open-label and multicenter study. The study consists of a Screening Phase (28 days prior to the first administration of the study drug), Treatment Phase (time when the first dose of ibrutinib is administered until disease progression, the investigator no longer considers the treatment to be tolerable, or the participant meets any one of the discontinuation criteria) and Follow-up Phase (end of the last dose of study drug until 30 days after the last dose of study drug or the start of subsequent anti-CLL/SLL therapy, whichever comes first). Participants will be instructed to take 3 capsules of ibrutinib (at a dose of 420 mg) orally once daily starting at Cycle 1, Day 1. Participants' safety will be monitored throughout the study.

Inclusion Criteria:

• Diagnosis of lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) that meets published diagnostic criteria
• For CLL participants: Measurable nodal disease by computed tomography (CT), defined as at least 1 lymph node greater than (>) 1.5 centimeter (cm) at the longest diameter at a site that has not been previously irradiated. Adequate hepatic function, defined as serum aspartate transaminase (AST) and alanine; For SLL participants: At least 1 measurable site of disease according to the Revised Response Criteria for Malignant Lymphoma
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
• Adequate hepatic function, defined as serum aspartate transaminase (AST) and alanine transaminase (ALT) <2.5 × upper limit of normal (ULN), and total bilirubin less than or equal to (<=) 1.5 × ULN (unless due to Gilbert's syndrome)
• A woman of childbearing potential must have a negative serum (beta-human chorionic gonadotropin [beta-hCG]) or urine pregnancy test at screening

Exclusion Criteria:

• Known involvement of the central nervous system by lymphoma or leukemia
• History or current evidence of Richter's transformation or prolymphocytic leukemia
• Uncontrolled autoimmune hemolytic anemia or idiopathic thrombocytopenic purpura
• Any previous treatment (chemotherapy, radiotherapy, and/or monoclonal antibodies) intended specifically to treat CLL/SLL
• Received any immunotherapy, live vaccine, or investigational drug within 4 weeks prior to the first dose of the study drug