This clinical trial is focused on studying a type of cancer called Diffuse Large B-Cell Lymphoma (DLBCL), which is a form of non-Hodgkin lymphoma. The study is specifically looking at patients whose DLBCL has returned or has not responded to previous treatments. The trial is testing a combination of medications to see if they can improve treatment outcomes for these patients. The medications being studied include Polatuzumab Vedotin, known by its code name RO5541077, and Rituximab, which are both given as infusions. These are combined with two chemotherapy drugs, Gemcitabine and Oxaliplatin, which are also administered through infusions. Some patients will receive all four medications, while others will receive only Rituximab, Gemcitabine, and Oxaliplatin, along with a placebo.

The purpose of the study is to evaluate the safety and effectiveness of the combination treatment compared to the standard treatment without Polatuzumab Vedotin. The study will monitor how well patients respond to the treatment and how long they live after receiving it. It will also look at any side effects, with a particular focus on a condition called peripheral neuropathy, which involves nerve damage that can cause weakness, numbness, and pain, usually in the hands and feet.

Participants in the study will receive their treatments through intravenous infusions, which means the medication is delivered directly into a vein. The study will take place over a period of time, with regular check-ups to monitor the patients’ health and response to the treatment. The trial aims to provide valuable information that could lead to better treatment options for patients with relapsed or refractory DLBCL.