Study to Evaluate Efficacy and Safety of Oral Abexinostat in Patients With Relapsed or Refractory Diffuse Large B-cell Lymphoma (DLBCL)

Inclusion Criteria: 1. Histologically confirmed diffuse large B-cell lymphoma (DLBCL); 2. Have received only two prior standard therapy lines for diffuse large B-cell lymphoma (DLBCL) including anti- cluster of differentiation antigen (anti-CD20) antibody and cytotoxic therapy; 3. Confirmed to be unresponsive to the last line of therapy, or have disease progression following the last line of therapy; 4. Have at least one radiologically measurable lymph node or extranodal lymphoid malignant lesion; 5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2; 6. Meet various hematological, liver and renal function lab parameters. Exclusion Criteria: 1. Have primary central nervous system (CNS) lymphoma or secondary central nervous system (CNS) infiltration, transformed lymphoma, unclassified B-cell lymphoma with features intermediate between DLBCL and classical Hodgkin's lymphoma (HL), primary effusion lymphoma, plasma lymphoma; 2. Toxicity not yet recovered from previous anti-tumor therapies; 3. Uncontrolled systemic infections or infections requiring intravenous antibiotics; 4. Have received steroid hormone, chemotherapy, targeted therapy, radiotherapy, antibody-based therapies, within a specified amount of time per protocol; 5. Unable to swallow tablets, or presence of significant functional gastrointestinal disorders that may affect the intake, transport or absorption of the study drug; 6. Have received autologous stem cell transplant,or allogeneic stem cell transplant within a certain amount of time as specified in protocol; 7. Presence of active graft-versus-host reaction; 8. Have undergone a major surgery within the last month; 9. Evidence of possible human immunodeficiency virus (HIV) infection or hepatitis C virus (HCV) infection; 10. Have any cardiac impairment as defined per protocol; 11. Have prior history of malignancies other than diffuse large B-cell lymphoma (DLBCL).