Engineering Naturally Occurring CD7 Negative T Cells for the Immunotherapy of Hematological Malignancies.

Chimeric antigen receptor (CAR) T cell therapy targeting T-cell acute lymphoblastic leukemia (T-ALL) faces limitations such as antigen selection and limited T-cell persistence. CD7 is an attractive antigen for targeting T-ALL, but overlapping expression on healthy T cells leads to fratricide of CD7-CAR T cells, requiring additional genetic modification. We took advantage of naturally occurring CD7- T cells to generate CD7-CAR (CD7-CARCD7-)T cells. CD7-CARCD7- T cells exhibited a predominantly CD4+ memory phenotype and had significant antitumor activity upon chronic antigen exposure in vitro and in xenograft mouse models. Based on these encouraging results, we next explored the utility of CD7- T cells for the immunotherapy of CD19+ hematological malignancies. Direct comparison of non-selected (bulk) CD19-CAR and CD19-CARCD7- T cells revealed that CD19-CARCD7- T cells had enhanced antitumor activity compared to their bulk counterparts in vitro and in vivo. Lastly, to gain insight into the behavior of CD19-CAR T cells with low levels of CD7 gene expression (CD7lo) in humans, we mined single-cell gene and T-cell receptor (TCR) expression data sets from our institutional CD19-CAR T-cell clinical study. CD19-CARCD7lo T cells were present in the initial CD19-CAR T-cell product and could be detected post-infusion. Intriguingly, the only functional CD4+ CD19-CAR T-cell cluster observed post-infusion exhibited CD7lo expression. Additionally, samples from patients responsive to therapy had a higher proportion of CD7lo T cells than in non-responders. Thus, CARCD7- T cells have favorable biological characteristics and may present a promising T-cell subset for adoptive cell therapy of T-ALL and other hematological malignancies.