A Phase II Study of Oral Panobinostat (LBH589) and Rituximab to Treat Diffuse Large B Cell Lymphoma (DLBCL)

Inclusion Criteria: * Pathological confirmation of any stage of DLBCL. Patients with transformation to DLBCL will be permitted on study. * Patients must have received at least 1 prior line of treatment if not eligible for an autologous stem cell transplant (ASCT) or 2 prior therapies, one of which must have been an ASCT, if eligible for such therapy. * Patients must have received prior rituximab therapy and the last treatment administered with rituximab must have been given at least 6 months prior to study registration on this trial. Exception may be granted to patients treated with rituximab or other anti-CD20 monoclonal antibody 3-6 months prior to study registration upon discussion with the Sponsor. * Patients must have at least one site of bi-dimensionally measurable lesion (\> 1.5 cm in its largest dimension by CT scan). * ECOG performance status of 0 or 1. * Age 18 years or older. * Baseline MUGA or ECHO must demonstrate LVEF ≥ the lower limit of the institutional normal (results 3 months prior to study registration is acceptable). * Provide written consent after the investigational nature, study design, risks and benefits of the study have been explained. Exclusion Criteria: * Prior use of any anti-CD20 monoclonal antibody within 6 months of study start (refer to inclusion #3 for exception). * History of serious infusion-related reaction to rituximab or other monoclonal antibodies. * Central nervous system lymphoma. * Prior treatment with HDAC, DAC, HSP90 inhibitors or valproic acid for the treatment of cancer. * Evidence of significant, uncontrolled concomitant disease which could affect compliance with the protocol or interpretation of results, including significant cardiovascular disease or pulmonary disease (including obstructive pulmonary disease and history of bronchospasm). * Impaired cardiac function * Uncontrolled hypertension. * Concomitant use of CYP3A4/5 inhibitors. * Concomitant use of drugs with a risk of causing "torsades de pointes". * Patients with unresolved diarrhea ≥ CTCAE grade 1. * Impairment of gastrointestinal function or GI disease that may significantly alter the absorption of oral LBH589. * Patients who have received treatment for DLBCL ≤ 3 weeks prior to starting the study treatment or who have not recovered from side effects of such therapy. * Women who are pregnant of breast feeding or women of childbearing potential (WOCBP) not willing to use a double barrier method of contraception during the study and 3 months after the end of treatment. One of these methods of contraception must be a barrier method. WOCBP are defined as sexually mature women who have not undergone a hysterectomy or who have not been naturally postmenopausal for at least 12 consecutive months (ie. who has had menses any time preceding 12 consecutive months). WOCBP must have a negative serum pregnancy test at baseline. * Male patients whose sexual partners are WOCBP not using double method of contraception during the study and 3 months after the end of treatment. One of these methods must be a condom. * Patients with a history of another primary malignancy within 5 years other than curatively treated CIS of the cervix, completely excised melanoma-in-situ, or basal or squamous cell carcinoma of the skin. * Patients with a known positivity for HIV or hepatitis C; baseline testing for HIV and hepatitis C is not required. * Patients with hepatitis B sAg positivity will be excluded. However, exceptions may be granted but only after discussion between the Sponsor and the site. Patients with hepatitis B core antibody positivity only must also be discussed with the Sponsor prior to entry on study (results 6 months prior to study registration is acceptable). * Patients who cannot stop ingestion of grapefruits, starfruit, or Seville oranges