Analysis of CD70 wild type or CD70 knock out CD70-specific nanoCAR T cells

CD70 is an attractive target for chimeric antigen receptor (CAR) T cell therapy as treatment for both solid and liquid malignancies. However, functionality of CD70-specific CAR T cells is only modest. Here, we optimized a CD70-specific VHH based CAR (nanoCAR). We evaluated the nanoCARs in clinically relevant models in vitro, using co-cultures of CD70-specific nanoCAR T cells with malignant rhabdoid tumor organoids, and in vivo by using a diffuse large B cell lymphoma (DLBCL) patient-derived xenograft (PDX) model. Whereas the nanoCAR T cells were highly efficient in organoid co-cultures, they showed only modest efficacy in the PDX model. Knocking out CD70 expression in the nanoCAR T cells resulted in dramatically enhanced functionality in the PDX model, suggesting that CD70 interaction in cis with the nanoCAR induces exhaustion. Through single-cell transcriptomics, we obtained evidence that CD70 KO CD70-specific nanoCAR T cells are protected from antigen-induced exhaustion. Our data show that CARs targeted to endogenous T cell antigens, negatively affect CAR T cell functionality by inducing an exhausted state, which can be overcome by knocking out the specific target, in this case CD70. Overall design: CD70 WT and CD70 KO CD70-specific nanoCAR T cells were isolated by Fluorescence-activated cell sorting (FACS) from bone marrow of mice injected with the Raji cell line. Sorting was performed based on CD45 and eGFP expression. Sorted cells were analyzed using scRNAseq.