A Study of Ibrutinib in Combination With Rituximab, in Japanese Participants With Waldenstrom's Macroglobulinemia (WM)

Inclusion Criteria

• Clinicopathological diagnosis of Waldenstrom's Macroglobulinemia (WM) in accordance with the consensus panel of the second International Workshop on Waldenstrom's Macroglobulinemia (IWWM)
• Japanese participants with treatment naïve or relapsed/refractory WM
• Measurable disease defined as serum monoclonal immunoglobulin M (IgM) greater than (>) 0.5 gram per deciliter (g/dL)
• Symptomatic disease, requiring treatment
• Eastern Cooperative Oncology Group (ECOG) performance status of less than or equal to ( 35 days from the most recent plasmapheresis procedure
• History of other malignancies
• Vaccinated with live, attenuated vaccines within 4 weeks of first dose of study drug
• Infection requiring systemic treatment that was completed <=14 days before the first dose of study drug
• Currently active, clinically significant Child-Pugh Class B or C hepatic impairment
• Inability or difficulty swallowing capsules, malabsorption syndrome, or any disease or medical condition significantly affecting gastrointestinal function
• Stroke or intracranial hemorrhage within 12 months prior to enrollment
• Currently active, clinically significant cardiovascular disease
• Requires treatment with a strong cytochrome P450 (CYP) 3A inhibitor
• Infection with human immunodeficiency virus (HIV) or active infection with hepatitis B or hepatitis C virus
• Major surgery within 4 weeks of first dose of study drug
• Lactating or pregnant
• Male participants who plan to father a child while enrolled in this study or within 3 months after the last dose of ibrutinib, and within 12 months after last dose of rituximab
• Any contraindication to ibrutinib or rituximab including hypersensitivity to the active substance or to any of the excipients of ibrutinib or rituximab per local prescribing information
• Received an investigational intervention (including investigational vaccines) or used an invasive investigational medical device within 4 weeks before the planned first dose of study intervention or is currently enrolled in an investigational study
• Any condition for which, in the opinion of the investigator, participation would not be in the best interest of the participant (eg [for example], compromise the wellbeing) or that could prevent, limit, or confound the protocol-specified assessments
• Employee of the investigator or study site, with direct involvement in the proposed study or other studies under the direction of that investigator or study site, as well as family members of the employees or the investigator