1MATCHED SIBLING DONOR-DERIVED PIGGYBAC CAR19 T CELLS INDUCE REMISSION OF RELAPSED/REFRACTORY CD19+ MALIGNANCY FOLLOWING HAEMATOPOIETIC STEM CELL TRANSPLANT

Background & Aim Aim The non-viral piggyBac transposon system reduces the complexity and expense of CAR T cell manufacture. piggyBac CAR19 T cells showed potent pre-clinical activity, so we now assess safety and clinical activity in a first-in-human study. Methods, Results & Conclusion Methods Eight patients (age 18-66 years, median 30; male n=7, female n=1) with relapsed/refractory CD19 + malignancies post HLA-matched sibling HSCT were treated with donor-derived T cells genetically modified using piggyBac to express a second-generation 4-1BB-based CAR19. The trial was conducted as an investigator-initiated study at a university hospital with local CAR19 T cell manufacture. CAR19 T cells were expanded ex vivo from 50 × 10 6 peripheral blood mononuclear cells , with CD19 stimulation and IL-15 support. Final products contained median 1.9 × 10 9 (range 0.8-2.5 × 10 9 ) total cells with 80.6% (39-93%) CAR T cells, and were generated in 15 (n=7) or 23 (n=1) days. Patients received up to 3 escalating doses of CAR19 T cells (10, 50 and 100 × 10 6 /m 2 ) following lymphodepleting cyclophosphamide and fludarabine (3 doses, n=5; 1 dose, n=3). Results Diagnoses were B-ALL (n=6), DLBCL (n=1), and Burkitt Lymphoma (n=1). Four patients each had a high or low burden of disease prior to treatment. The patient with Burkitt Lymphoma died of complications unrelated to CAR T cells 307 days with 3 doses. Toxicity included: cytokine release syndrome (n=3), B-cell aplasia with hypogammaglobulinaemia (n=7), prolonged cytopenias (n=6), bacterial infection (n=3) and exacerbation of chronic GVHD (n=1). No CAR T cell-related encephalopathy syndrome occurred. Conclusions Manufacture of piggyBac CAR19 T cells for clinical use is rapid, robust and uncomplicated, permitting application of this technology to multiple healthcare institutions. Early results suggest similar safety and activity to that of CAR19 T cells generated with viral vectors. The optimal CAR19 T cell dosing strategy remains to be determined.