EXTH-23. BICISTRONIC CAR-T CELLS TARGETING EGFR AND IL13RΑ2 MITIGATE ANTIGENIC HETEROGENEITY IN GLIOMA

Abstract Chimeric antigen receptor (CAR)-T cells have had a significant effect in hematological diseases, with a recent study confirming that the cells can last for ten years in vivo. Unfortunately, to date, CAR-T cells have had little effect in solid tumors. One cause of the treatment difficulty is antigenic heterogeneity. Our experience with CAR-T cells in glioblastoma suggests that addressing antigenic heterogeneity may improve the clinical efficacy. Targeting the epidermal growth factor receptor (EGFR) and interleukin 13 receptor subunit alpha 2 (IL13Rα2) individually could lead to tumor control in the short term, but it will be marked by tumor recurrence through antigen loss or downregulation in the long term. This resistance mechanism can be inhibited by combinatorial targeting. To this end, we have designed a bicistronic construct that targets both EGFR and IL13Rα2 simultaneously, to decrease the potential of antigen escape and tumor recurrence. The bicistronic CAR-T cells employ an “OR” logic gate to modify the T cells and kill the tumor cells in vitro and in vivo, in order to retain effectiveness when one target antigen is lost but the second is still present. Our experimental results demonstrate that and validate the safety and possibility of clinical translation. In addition, the efficiency of transfecting T cells with the single bicistronic vector was higher than two single vectors on monovalent CARs. In summary, the bicistronic CAR-T structure is a promising strategy to address the clinical problem of targeting antigenic heterogeneity in solid tumors and potentially level the barriers for targeted T-cell therapy. Educational Objectives: After completion, participants will be able to explain the importance of antigenic heterogeneity in solid tumors in the context of tumor escape. Participants will also be able to identify a strategy to reducing the problem of antigen escape and tumor recurrence through the implementation of bicistronic CARs.