The safety of CAR-T cells and PD-1 antibody combination on an experimental model

Chimeric antigen receptor (CAR) T cells and PD-1 antibodies (PD-1 Ab) are emergent immunotherapies with unprecedented efficacy. The presence of PD-1 on T cells contributes to hypofunction of CAR-T therapy and inhibition of PD-1 enhances anti-cancer effect of CAR-T cells. Therefore, the combination of CAR-T cells and PD-1 antibody is a promissing strategy for cancer treatment. This study aims to establish our in-house CAR-T cells and evaluate the safety of CAR-T cells in combination with PD-1 antibody in animals. The toxicity of CD19-CAR-T cells was examined using Swiss Webster mice. Four mouse groups were treated with control, CAR-T, PD-1 antibody or CAR-T + PD-1 antibody. Mice's overall status was monitored and recorded. At the end-point, hematological and biochemical indices were quantified, histopathology of liver and kidney was evaluated by pathologists. The relative abnormal ratio and absolute values were compared between groups. We generated our in-house CAR-T cells and used them for safety evaluation in mice. The increase in mouse weight was observed in all groups after treatment and the weight was comparable between groups. The hematological, biochemical and histopathological parameters were equivalent between groups, except for liver grain degeneration occurred in treatment groups. Thus, CAR-T cells, PD-1 Ab and their combination were safe in mice. We successfully produced our in-house CAR-T cells and the combination of our CAR-T cells and PD-1 antibody was safe in mice with comparable values of hematopoietic indices, liver and kidney functions. Longer follow-up might be necessary to evaluate their effect on the liver.