Primary Objectives:~To determine the safety of mosunetuzumab, polatuzumab vedotin, tafasitamab, and lenalidomide in relapsed/refractory NHL.~To determine the best overall response rate (ORR) of the combination of mosunetuzumab, with polatuzumab vedotin, tafasitamab, and lenalidomide in patients with relapsed/refractory diffuse large B-cell lymphoma.~Secondary Objectives:~To determine the complete response rate, duration of response, progression free survival, and overall survival in patients with DLBCL following treatment with of mosunetuzumab, polatuzumab vedotin, tafasitamab, and lenalidomide.~To evaluate changes in immune effector cells and the tumor microenvironment following treatment with of mosunetuzumab, polatuzumab vedotin, tafasitamab, and lenalidomide.
To learn if giving mosunetuzumab in combination with polatuzumab vedotin, tafasitamab, and lenalidomide can help to control relapsed/refractory FL and DLBCL.