Avelumab In Combination Regimens That Include An Immune Agonist, Epigenetic Modulator, CD20 Antagonist and/or Conventional Chemotherapy in Patients With Relapsed or Refractory Diffuse Large B-cell Lymphoma (R/R DLBCL)

Key Inclusion Criteria:

-Any of the following as defined by the WHO, 2016 lymphoid neoplasm classifications and histologically confirmed:

* Diffuse large B-cell lymphoma (DLBCL), Not Otherwise Specified (NOS): Germinal center B-cell type (GCB), Activated B-cell type (ABC)
* High-grade B-cell lymphoma (HGBCL) NOS
* HGBCL with MYC and BCL2 and/or BCL6 rearrangements
* T-cell histocyte-rich large B-cell lymphoma
* EBV+ DLBCL, NOS
* HHV8+ DLBCL, NOS

Relapsed or refractory disease following at least 2 lines (and a maximum of 4 lines) of prior rituximab containing multi-agent chemotherapy which may include an autologous stem cell transplantation unless patients are not considered suitable for intensive second-line chemotherapy or autologous stem cell transplantation. Patients who are ineligible for intensive second line chemotherapy,must have received at least one prior rituximab-containing combination chemotherapy regimen. Patients who are ineligible for intensive second line chemotherapy, must have received at least one prior rituximab-containing combination chemotherapy regimen.

* Baseline measurable disease with at least 1 bi dimensional lesion with longest diameter (LDi) \>1.5cm on CT scan which is FDG avid on PET scan.
* A biopsy (archived or Screening/recent) will be collected at Screening.
* At least 18years of age (or ≥20 years in Japan).
* Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 or 1.

Key Exclusion Criteria:

* Active central nervous system (CNS) lymphoma.
* Prior organ transplantation including prior allogeneic SCT.
* Prior therapy with an anti PD 1, anti PD L1, anti PD L2, anti CD137, or anti cytotoxic T lymphocyte associated antigen 4 (CTLA 4) antibody (including ipilimumab, tremelimumab or any other antibody, or drug specifically targeting T cell co stimulatory or immune checkpoint pathways).