This research study is for people who have been diagnosed with large B-cell lymphoma of the central nervous system (CNS), which has either returned or is not responding to current treatment. Goldcadomide is a new experimental drug that works by binding to a specific protein inside cancer cells and helps stimulate immune cells that help fight cancer cells. It also has the ability to enter the central nervous system. It has shown promising safety and effectiveness when combined with standard of care chemotherapy. Participants will be treated with this study drug combined with standard of care chemotherapy. Participation in the research will last about 2.5 years. The purpose of this study is to help researchers learn if the study drug, Golcadomide, in combination with the standard of care regimen is a safe and effective way to treat large B-cell lymphoma with CNS involvement.