• Men and women ≥ 60 years of age.

• Pathologically confirmed MCL, with documentation of monoclonal B cells that have a chromosome translocation t(11;14)(q13;q32) and/or overexpress cyclin D1.

• Stage II-IV MCL and requiring treatment in the opinion of the treating clinician.

• Eastern Cooperative Oncology Group (ECOG) performance status 0-3

• One or more of the following:

‣ Age 80 years or more

⁃ Cumulative Illness Rating Scale for Geriatrics (CIRS-G) score 6 or greater

⁃ Left ventricular ejection fraction (LVEF) less than or equal to 50% as assessed by echocardiogram

⁃ Significant co-morbidities or cardiac risk factors making anthracycline-containing chemotherapy inadvisable

⁃ Heart failure clinically determined by the presence of New York Heart Association (NYHA) failure grade II due to a cause other than MCL

⁃ Impaired respiratory function with DLCO and/or FVC/FEV1 ratio less than 75% of predicted due to a cause other than MCL

⁃ Significant respiratory illness e.g. moderate chronic obstructive pulmonary disease (COPD) bronchiectasis

⁃ Other co-morbidities that in the Investigator's opinion which would preclude the use of standard full dose immuno-chemotherapy (to be discussed on a case-by-case basis with the TMG, via UCL CTC)

• Willing and able to participate in all required evaluations and procedures in this study protocol including swallowing capsules/tablets without difficulty.

• Negative serum or urine pregnancy test for women of childbearing potential (WOCBP).

• Willing to comply with the contraceptive requirements of the trial.

• Written informed consent.