Inclusion Criteria:  Male and female participants aged 18 years or older. (Japan aged 20 years or older.) Have received no previous systemic anti-lymphoma therapies. Pathologically confirmed MCL by local laboratory. Histologically confirmed CD20 expression (by flow cytometry or immunohistochemistry) of the MCL cells as assessed by pathology. Ineligible for high-dose chemotherapy and autologous stem cell transplantation. Radiographically (CT, MRI) measurable lymphadenopathy per the Lugano criteria for response assessment (Cheson et al 2014). ECOG PS of 0 to 2. Willingness to avoid pregnancy or fathering children.  Exclusion Criteria:  Presence of any lymphoma other than MCL. Presence of CNS lymphoma (either primary or secondary) or leptomeningeal disease. Requires treatment with potent inducers and inhibitors of CYP3A4 Inadequate organ functions including hematopoiesis, liver, and kidney significant concurrent, uncontrolled medical condition, including, but not limited to, renal, hepatic, hematological, GI, endocrine, pulmonary, neurological, cerebral, or psychiatric disease. History of other malignancy within 2 years of study entry. Known HIV infection, HBV or HCV. HBV or HCV infection: Participants positive for HBsAg or anti-HBc will be eligible if they are negative for HBV-DNA; these participants must receive prophylactic antiviral therapy. Participant's positive for HCV antibody will be eligible if they are negative for HCV-RNA. Clinically significant cardiac disease, congestive heart failure, including unstable angina, acute myocardial infarction, or cardiac conduction issues, within 6 months of randomization. Abnormal ECG findings that are clinically meaningful per investigator's assessment. Women who are pregnant or breastfeeding Any condition that would, in the investigator's judgment, interfere with full participation in the study, including administration of study treatment and attending required study visits; pose a significant risk to the participant; or interfere with interpretation of study data.