Inclusion Criteria:

          -  Confirmed MCL diagnosis

          -  Previously treated with at least one prior line of systemic therapy for MCL

          -  Measurable disease per Lugano criteria

          -  Eastern Cooperative Oncology Group (ECOG) 0-2

          -  Absolute neutrophil count ≥ 0.75 × 109/L without granulocyte-colony stimulating factor
             support within 7 days of screening

          -  Hemoglobin ≥ 8 g/dL not requiring transfusion support or growth factors within 7 days
             of screening

          -  Platelets ≥ 50 × 109/L not requiring transfusion support or growth factors within 7
             days of screening.

          -  AST and ALT ≤ 3.0 x upper limit of normal (ULN).

          -  Total bilirubin ≤ 1.5 x ULN.

          -  Creatinine clearance of ≥ 30 mL/min according to Cockcroft/Gault Formula

        Exclusion Criteria:

          -  Prior treatment with an approved or investigational BTK inhibitor

          -  History of bleeding diathesis

          -  History of stroke or intracranial hemorrhage within 6 months of randomization

          -  History of allogeneic or autologous stem cell transplant (SCT) or chimeric antigen
             receptor modified T-cell (CAR-T) therapy within 60 days of randomization

          -  Clinically significant cardiovascular disease

          -  Prolonged QT interval corrected using Fridericia's formula (QTcF) > 470 ms on 2/3
             consecutive ECGs, and mean QTcF>470 ms on all 3 ECGs

          -  Known HIV infection or active HBV, HCV, or CMV infections

          -  Clinically significant active malabsorption syndrome or other condition likely to
             affect gastrointestinal (GI) absorption

          -  Current treatment with strong cytochrome P450 3A4 (CYP3A4) inhibitors or inducers
             and/or strong P-gp inhibitors.

          -  Patients requiring therapeutic anticoagulation with warfarin or another Vitamin K
             antagonist.

          -  Vaccination with live vaccine within 28 days prior to randomization