Study Investigating the Safety and Efficacy of Blinatumomab in Combination With Pembrolizumab in Adults With Relapsed or Refractory Diffuse Large B Cell Lymphoma (DLBCL)

Inclusion Criteria: * Have histologically confirmed diffuse large B-cell lymphoma that is either: * Refractory after at least one regimen of systemic chemotherapy and/or targeted therapy, or * In first or later relapse if have received at least 2 systemic regimens since time of diagnosis, or * Relapsed post-autologous or allogeneic hematopoietic stem cell transplantation (HSCT) with adequate organ function after proximity to transplantation time exclusions * Have measurable disease * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 * Life expectancy of ≥ 12 weeks in the opinion of the Investigator * Biopsy proven DLBCL (biopsy proven at least at primary diagnosis of DLBCL) Other Inclusion Criteria May Apply Exclusion Criteria: * Richter's transformation (DLBCL arising in the setting of prior chronic lymphocytic leukemia) or primary mediastinal B cell lymphoma (PMBCL) * History or presence of clinically relevant central nervous system pathology such as epilepsy, paresis, aphasia, stroke, severe brain injury, dementia, Parkinson's disease, cerebellar disease, organic brain syndrome, or psychosis. * Has a diagnosis of immunodeficiency or has received systemic steroid therapy (in excess of 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of protocol specified therapy. * Has undergone prior allogeneic HSCT: * within the last 5 years OR * greater than 5 years ago but has active graft versu…