Low-cost generation of Good Manufacturing Practice-grade CD19-specific chimeric antigen receptor-expressing T cells using piggyBac gene transfer and patient-derived materials

Background aims: Protocols for the production of CD19-specific chimeric antigen receptor (CAR19) T cells are often complex and expensive because of the use of retroviral and lentiviral vectors or the need for CAR19 T-cell enrichment. We aimed to simplify the generation of CAR19 T cells from the peripheral blood of normal donors and patients using the piggyBac transposon system of gene modification. Methods: We varied electroporation voltage, cytokines and stimulation conditions for the generation and expansion of CAR19 T cells over a 3-week culture period. Results: Using optimized electroporation voltage, interleukin-15 alone and co-culturing CAR T cells with peripheral blood mononuclear cells, we were able to expand CAR19 T-cell cultures by up to 765-fold over 3 weeks in normal donors and 180-fold in patients with B-cell malignancies. Final median CAR19 expression of 72% was seen in normal donors, and 81% was seen in patients with acute lymphoblastic leukaemia, chronic lymphocytic leukemia or non-Hodgkin lymphoma. CAR19 T cells produced interferon gamma on stimulation with CD19⁺ cell lines and efficiently lysed both CD19⁺ cell lines and primary leukemia cells. In addition, combining CAR expression with an inducible caspase safety switch allowed elimination of CAR19 T cells by the application of a small molecule dimerizer. Discussion: We have produced a simple, inexpensive and easily adoptable protocol for the generation of CAR19 T cells suitable for use in clinical trials using the piggyBac transposon system. This provides a robust platform for further enhancing the T-cell product and testing new CAR technologies.