Double CD19/CD22 Chimeric Antigen Receptor-Modified T Cells for the Treatment of Stage IV Relapsed and Refractory Follicular Lymphoma

Background: In recent years, frontline rituximab combined with chemotherapy in the treatment of refractory follicular lymphoma (FL) has greatly improved progression free survival. Nevertheless, advanced relapsed/refractory FL is still incurable and novel therapeutics are needed. FL is a B cell maligancy and immunotherapy based on chimeric antigen receptor-modified T cells (CARTs) may improve late stage patient outcomes. In this study, we report the safety and efficacy of combining CD19/CD22 targeted CARTs to treat an advanced stage IV FL patient with widespread tumor masses, as well as blood and bone marrow (BM) involvement.

Patient and Method: The patient, 31 yr old male, presented with swallen neck, abdominal mass and enlarged spleen and liver. Lymphnode biopsies were positive for CD19, CD20, Pax-5, CD3 (diffused), Bcl-2, CD21, CD10, Ki67 >20% and t(14;18). BM biopsies showed abnormal blasts of mature B cells, positive for CD45, CD20, CD22, CD10, HLA-DR, cCD79a, sKappa, Bcl-2 and partial CD19 and FMC7, diagnosed as FL stage IV with BM involvement. After 4x R-CHOP, the patient achieved CR, and completed total 8 cycles of treatment. The disease relapsed after 16 months with extensive tumor masses in abdominal lymphnodes and 87% lymphoblast tumors in the peripheral blood. The patient failed to respond to additional 2x R-CHOP and a second line R-ESHAP, and enrolled in the trial, "Combination CAR T cell therapy targeting hematological malignancies" (clinicaltrial.gov registry NCT03125577). CD3 positive cells were selected and activated for lentiviral infection. To prevent CD19 target escape, T cells were transduced with a fourth generation caspase 9-inducible, safety-engineered lentivector CAR containing several binding and signaling domains: CD19- and CD22-scFv/CD28/CD27/CD3ζ-iCasp9 (4SCAR19 and 4SCAR22). The patient received cyclophosphamide (800mg/m²) for 3 days as conditioning regimen before the first CART infusion, and a second round of CART infusions on day 6. The total infused CARTs were 0.65-2.25x106/kg.

Results: After infusion, the patient experienced mild fever (39^oC), increased C-reactive protein and sore throat on day 8 with no signs of infection and mild cytokine release syndrome (CRS grade 0-1). Quantitative PCR analysis of CART in peripheral blood mononuclear cells detected 0.02%, 1.02% and 0.14% on day 6 , 12 and 21, respectively. On day 60, WBC, platelet count became normal and BM showed increased nucleated cell proliferation with no abnormality. Examinaiton for minimal residual disease showed CD19 positive cells at 0.2% with no abnormal immunophenotype. The patient achieved CR both in blood and BM 5 months after the double CART infusions. After 9 months, CT and PET-CT reports showed no detectable lymphnode tumor, normal spleen size, and complete disappearance of tumor mass previously surrounding the abdominal aorta and the iliac artery.

Conclusion: This is the first report of high-risk stage IV FL with widespread tumors, BM and peripheral blood involvement, treated with double CD19/CD22 targeting CARTs, and achieved CR with little to no adverse effects. The patient did not develop any complications during the treatment. This CD19/CD22 double CART infusion protocol could be a safe and effective therapeutic option for advanced FL that has failed all available treatmets, and further, it may prevent possible CD19 negative clonal relapse.