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