Inclusion Criteria:

• Men and women ≥ 18 years of age
• ECOG performance status of ≤ 2
• Pathologically confirmed MCL, with documentation of either overexpression of cyclin D1 or t(11;14), and measurable disease on cross sectional imaging that is ≥ 2 cm in the longest diameter and measurable in 2 perpendicular dimensions
• Documented failure to achieve at least partial response (PR) with, or documented disease progression disease after, the most recent treatment regimen
• At least 1, but no more than 5, prior treatment regimens for MCL (Note: Subjects having received ≥2 cycles of prior treatment with bortezomib, either as a single agent or as part of a combination therapy regimen, will be considered to be bortezomib-exposed.)
• Willing and able to participate in all required evaluations and procedures in this study protocol including swallowing capsules without difficulty
• Ability to understand the purpose and risks of the study and provide signed and dated informed consent and authorization to use protected health information (in accordance with national and local subject privacy regulations)

Major exclusion criteria:

• Prior chemotherapy within 3 weeks, nitrosoureas within 6 weeks, therapeutic anticancer antibodies within 4 weeks, radio- or toxin-immunoconjugates within 10 weeks, radiation therapy within 3 weeks, or major surgery within 2 weeks of first dose of study drug
• Any life-threatening illness, medical condition or organ system dysfunction which, in the investigator's opinion, could compromise the subject's safety, interfere with the absorption or metabolism of PCI-32765 capsules, or put the study outcomes at undue risk
• Clinically significant cardiovascular disease such as uncontrolled or symptomatic arrhythmias, congestive heart failure, or myocardial infarction within 6 months of screening, or any Class 3 or 4 cardiac disease as defined by the New York Heart Association Functional Classification
• Malabsorption syndrome, disease significantly affecting gastrointestinal function, or resection of the stomach or small bowel or ulcerative colitis, symptomatic inflammatory bowel disease, or partial or complete bowel obstruction

• Any of the following laboratory abnormalities:

  1. Absolute neutrophil count (ANC) < 750 cells/mm3 (0.75 x 109/L) unless there is documented bone marrow involvement
  2. Platelet count < 50,000 cells/mm3 (50 x 109/L) independent of transfusion support unless there is documented bone marrow involvement
  3. Serum aspartate transaminase (AST/SGOT) or alanine transaminase (ALT/SGPT) ≥ 3.0 x upper limit of normal (ULN)
  4. Creatinine > 2.0 x ULN