This clinical trial is focused on studying a type of cancer called Follicular Lymphoma, which is a form of non-Hodgkin lymphoma. The study is investigating the effectiveness and safety of a new treatment combination for patients who have not received any prior treatment for this condition. The treatment being tested includes a combination of three medications: Epcoritamab, Rituximab, and Lenalidomide. Epcoritamab is a type of medication known as a bispecific antibody, which is designed to help the immune system target and destroy cancer cells. Rituximab is a chimeric monoclonal antibody that also helps the immune system attack cancer cells, while Lenalidomide is a medication that affects the immune system and has anti-cancer properties.

The purpose of this study is to determine if the combination of Epcoritamab, Rituximab, and Lenalidomide can improve the rate of complete response, meaning the disappearance of all signs of cancer, compared to the standard treatment known as chemoimmunotherapy. Participants in the study will be randomly assigned to receive either the new combination treatment or the standard treatment. The study will monitor participants over a period of time to assess the safety of the treatments and any changes in the activity of the disease. The study will also look at other outcomes, such as progression-free survival, which is the length of time during and after treatment that a patient lives with the disease without it getting worse, and overall survival, which is the length of time from the start of treatment that patients are still alive.

Throughout the study, participants will receive their treatments either through subcutaneous injection, which is an injection under the skin, or intravenous infusion, which is an injection into a vein, depending on the medication. The study aims to provide valuable information on whether this new combination of treatments can offer a better outcome for patients with previously untreated Follicular Lymphoma compared to existing treatment options. Participants will be closely monitored for any adverse events, which are any unwanted effects of the treatment, to ensure their safety throughout the study.