Sleeping Beauty Engineered Car T Cells Achieve Antileukemic Activity Without Severe Toxicities

BACKGROUND. Chimeric antigen receptor (CAR) T cell immunotherapy has resulted in complete remission (CR) and durable response in highly refractory patients. However, logistical complexity and high costs of manufacturing autologous viral products limit CART cell availability.METHODS. We report the early results of a phase I/II trial in B cell acute lymphoblastic leukemia (B-ALL) patients relapsed after allogeneic hematopoietic stem cell transplantation (HSCT) using donor-derived CD19 CART cells generated with the Sleeping Beauty (SB) transposon and differentiated into cytokine-induced killer (CIK) cells.RESULTS. The cellular product was produced successfully for all patients from the donor peripheral blood (PB) and consisted mostly of CD3+ lymphocytes with 43% CAR expression. Four pediatric and 9 adult patients were infused with a single dose of CART cells. Toxicities reported were 2 grade I and 1 grade II cytokine-release syndrome (CRS) cases at the highest dose in the absence of graft-versus-host disease (GVHD), neurotoxicity, or dose-limiting toxicities. Six out of 7 patients receiving the highest doses achieved CR and CR with incomplete blood count recovery (CRi) at day 28. Five out of 6 patients in CR were also minimal residual disease negative (MRD-). Robust expansion was achieved in the majority of the patients. CART cells were measurable by transgene copy PCR up to 10 months. Integration site analysis showed a positive safety profile and highly polyclonal repertoire in vitro and at early time points after infusion.CONCLUSION. SB-engineered CART cells expand and persist in pediatric and adult B-ALL patients relapsed after HSCT. Antileukemic activity was achieved without severe toxicities.