This phase I trial studies the side effects and best dose of mosunetuzumab when given together with polatuzumab vedotin and lenalidomide in treating patients with diffuse large B-cell lymphoma (DLBCL) that has come back after a period of improvement (relapsed) or that has not responded to previous treatment (refractory). Mosunetuzumab and polatuzumab vedotin are monoclonal antibodies that may interfere with the ability of cancer cells to grow and spread. Polatuzumab, linked to a toxic agent called vedotin, attaches to CD79B positive cancer cells in a targeted way and delivers vedotin to kill them. Lenalidomide may stimulate or suppress the immune system in different ways and stop cancer cells from growing and by preventing the growth of new blood vessels that cancer cells need to grow. Giving mosunetuzumab with polatuzumab vedotin and lenalidomide may work better in treating patients with relapsed/refractory DLBCL.
Patients must have histologically confirmed DLBCL NOS, high-grade B-cell lymphoma, or transformed indolent lymphoma as per the World Health Organization 2022 criteria
All patients will have relapsed/refractory DLBCL after 1 or more prior lines of therapy with the exception of patients receiving CAR T in second line that have a D score of 3 at day (D)+ 30 through D+ 90
Patients who progressed/relapsed after prior polatuzumab vedotin are allowed
For the expansion cohorts only: cohort A must have Deauville score of ≥ 3 with the first 90 days) after standard of care chimeric antigen receptor (CAR) T-cell therapy; cohort B- other patients with relapsed/refractory after 1 or more prior lines of therapy (e.g. relapse after Day 90 from CAR-T, or relapsed after other therapies and were not considered candidates for CAR-T)
Plasmablastic lymphoma, primary mediastinal B-cell lymphoma, gray zone lymphoma
Patients who have not recovered from adverse events due to prior anti-cancer therapy (i.e., have residual toxicities > grade 1) with the exception of alopecia
Patients who are receiving any other investigational agents or treatments
Any condition, including the presence of laboratory abnormalities, which places the subject at unacceptable risk if he/she were to participate in the study or confounds the ability to interpret data from the study