Fludarabine and Cyclophosphamide With or Without Rituximab Before CD19 Chimeric Antigen Receptor T Cells for the Treatment of Relapsed or Refractory Diffuse Large B-Cell Lymphoma

PRIMARY OBJECTIVES:I. To examine the feasibility to manufacture autologous CD19 CAR T cells at a minimum target dose of 1.0 x 10\^6 cells/kilogram using the CliniMACS automated system.II. To determine the safety of administering high-dose conditioning chemotherapy with cyclophosphamide and fludarabine with rituximab prior to CD19 CAR-T cell therapy in patients with relapsed (R)/refractory (R) diffuse large B cell lymphoma (DLBCL) and to find the recommended regimen after phase II dose for this therapy.III. To determine the safety of infusion of chimeric antigen receptor T cells targeting CD19 in adults with R/R DLBCL. SECONDARY OBJECTIVES:I. To describe the toxicities related to CD19 targeted CAR T cells.II. To describe the overall response rate (ORR) and complete response (CR) rate of relapsed DLBCL treated with CD19 CAR T cells.III. To assess other response variables including overall survival (OS), progression free survival (PFS), and event free survival (EFS). OUTLINE: This is a dose-escalation study. Patients are assigned to 1 of 6 dose levels. DOSE LEVEL 1: Patients receive fludarabine phosphate intravenously (IV) over 30 minutes daily and cyclophosphamide IV over 60 minutes daily on days -5 to -3. Patients also receive CD19 CAR T cells IV on day 0. DOSE LEVEL 2: Patients receive rituximab IV on day -5, fludarabine phosphate IV over 30 minutes daily on days -5 to -3, and cyclophosphamide IV over 60 minutes on days -5 to -3. Patients also receive CD19 CAR T cells IV on day 0. DOSE LEVEL 3: Patients receive fludarabine phosphate IV over 30 minutes daily on days -3 to -5 and cyclophosphamide IV over 60 minutes daily on day -5. Patients also receive CD19 CAR T cells IV on day 0.DOSE LEVEL 4: Patients receive rituximab IV on day -5, fludarabine phosphate IV over 30 minutes daily on days -5 to -3, and cyclophosphamide IV over 60 minutes on day -5. Patients also receive CD19 CAR T cells IV on day 0. DOSE LEVEL 5: Patients receive fludarabine phosphate IV over 30 minutes daily on days -5 to -1 and cyclophosphamide IV over 60 minutes daily on days -5 and -4. Patients also receive CD19 CAR T cells IV on day 0. DOSE LEVEL 6: Patients receive rituximab IV on day -5, fludarabine phosphate IV over 30 minutes daily on days -5 to -1, and cyclophosphamide IV over 60 minutes on days -5 and -4. Patients also receive CD19 CAR T cells IV on day 0.After completion of study treatment, patients are followed up at 30, 60, and 90 days, 6 and 12 months, and then annually for up to 15 years.