PRIMARY OBJECTIVE:~I. To estimate the rate of complete response (CR) after 4 cycles of weekly (or 7-day) treatments with combined rituximab and tafasitamab in subjects with post-transplant lymphoproliferative disorder (PTLD).~SECONDARY OBJECTIVES:~I. To describe the safety profile of treatment with combined rituximab and tafasitamab in subjects with PTLD.~II. To estimate the objective response rate (ORR), defined as clinical response (CR + partial response [PR]) after 4 cycles of weekly (or 7-day) treatments with combined rituximab and tafasitamab in subjects with PTLD.~III. To determine the best overall response (BOR), defined as best clinical response (CR + PR) at either the completion of 4 cycles of weekly (or 7-day) treatments or 4 consolidation cycles (every 3 week) of combined rituximab and tafasitamab in subjects with PTLD.~IV. To estimate the rate of complete response (CR) after completion of consolidation treatments of combined rituximab and tafasitamab in subjects with PTLD.~V. To estimate the progression free survival (PFS) in subjects with PTLD treated with rituximab and tafasitamab.~VI. To estimate the overall survival (OS) in subjects with PTLD treated with rituximab and tafasitamab.~EXPLORATORY OBJECTIVES:~I. To describe baseline CD19 and CD20 expression on malignant lymphocytes by flow cytometry in subjects with PTLD.~II. To describe the relationship of tumor microenvironment characteristics using ribonucleic acid sequencing (RNASeq) with clinical response to combined rituximab and tafasitamab in subjects with PTLD.~III. To characterize the peripheral immunophenotype changes using cytometry by time-of-flight (CyTOF) from cycle 1 (C1) day 1 (D1) to cycle 5 (C5)D1 of combined rituximab and tafasitamab in subjects with PTLD.~IV. To describe the type of immunosuppression and amount reduced in subjects with PTLD.~V. To describe the relationship between metabolic tumor volume at diagnosis and response to combined rituximab and tafasitamab in subjects with PTLD.~VI. To characterize Epstein-barr virus (EBV) methylation alterations in EBV positive PTLDs.~OUTLINE:~Patients receive tafasitamab intravenously (IV) and rituximab IV or subcutaneously (SC) on study. Patients who have CR or PR after 4 cycles may receive additional tafasitamab and rituximab on study. Patients also undergo positron emission tomography (PET) or computed tomography (CT), biopsy, and collection of blood samples throughout the trial.
This phase II trial tests how well tafasitamab and rituximab work for front-line treatment of patients with post-transplant lymphoproliferative disorder. Post-transplant lymphoproliferative disorder (PTLD) is the name for types of lymphoma that sometimes develop in people who have had a transplant. It can affect people who are taking medicines to suppress their immune system. Tafasitamab injection is in a class of medications called monoclonal antibodies. It works by helping the body to slow or stop the growth of cancer cells. Rituximab is a monoclonal antibody. It binds to a protein called CD20, which is found on B cells (a type of white blood cell) and some types of cancer cells. This may help the immune system kill cancer cells. Giving the combination of tafasitamab and rituximab may work better in treating patients with post-transplant lymphoproliferative disorder.