A Study of BR Alone Versus in Combination With Acalabrutinib in Subjects With Previously Untreated MCL

Inclusion Criteria: * Men and women, ≥ 65 years of age. * Pathologically confirmed MCL, with documentation of a chromosome translocation t(11;14)(q13;q32) and/or overexpression of cyclin D1 in association with other relevant markers (eg, CD5, CD19, CD20, PAX5) . * MCL requiring treatment and for which no prior systemic anticancer therapies have been received. * Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 2. * Agreement to use highly effective forms of contraception during the study and 6 months after the last dose of bendamustine, or 12 months after the last dose of rituximab, whichever is longest . Exclusion Criteria: * Significant cardiovascular disease such as uncontrolled or symptomatic arrhythmias, congestive heart failure, or myocardial infarction within 6 months of first dose of study drug, or any Class 3 or 4 cardiac disease as defined by the New York Heart Association Functional Classification, or corrected QT interval (QTc) \> 480 msec (calculated using Friderica's formula: QT/RR0.33) at screening. Exception: Subjects with controlled, asymptomatic atrial fibrillation during screening are allowed to enroll on study. * Malabsorption syndrome, disease significantly affecting gastrointestinal function, resection of the stomach, extensive small bowel resection that is likely to affect absorption, symptomatic inflammatory bowel disease, partial or complete bowel obstruction, or gastric restrictions and bariatric surgery, such as gastric bypass. * Uncontrolled active systemic fungal, bacterial, viral, or other infection (defined as exhibiting ongoing signs/symptoms related to the infection and without improvement, despite appropriate antibiotics or other treatment), or intravenous anti infective treatment within 2 weeks before first dose of study drug. * Concurrent participation in another therapeutic clinical trial.