Diffuse Large B-Cell Lymphoma (DLBCL) Clinical Trials

This study is researching an experimental drug called odronextamab, referred to as study drug, when used in combination with chemotherapy. The study is focused on patients with Diffuse Large B-cell Lymphoma (DLBCL) that have not been treated before (called previously untreated). Patients with DLBCL that have come back after treatment (called relapsed), or have not responded to treatment (called refractory), can also participate in this study. This study will be made up of Part 1A, Part 1B, and Part 2.The aim of Part 1A and Part 1B of the study is to see how safe and tolerable the study drug in combination with chemotherapy is and to determine the dose and schedule of the study drug to be combined with chemotherapy in Part 2 of the study. The aim of Part 2 of the study is to see how effective the combination of the study drug with chemotherapy is in comparison with the combination of rituximab (the comparator drug), and chemotherapy, the current standard of care treatment approved for DLBCL. Standard of care means the usual medication expected and used when receiving treatment for a condition. The study is looking at several other research questions, including: * What side effects may happen from taking the study drug when combined with chemotherapy * How much study drug is in the blood at different times * Whether the body makes antibodies against the study drug (which could make the study drug less effective or could lead to side effects) * The impact from the study drug on quality of life and ability to complete routine daily activities