Humanized CD70-targeted CAR-T cells with reduced fratricide demonstrate potent antitumor activity against AML and RCC

Chimeric antigen receptor (CAR)-T cell therapy has achieved remarkable success in B-cell malignancies, but its application in acute myeloid leukemia (AML) and renal cell carcinoma (RCC) remains challenging due to the lack of ideal target antigens. CD70 is highly expressed on AML and RCC tumor cells, while its expression in normal tissues is largely restricted to activated lymphocytes, making it a promising immunotherapeutic target. However, CD70 expression on activated T cells can trigger fratricide in CD70-targeted CAR-T cells, posing a major challenge for their preparation and efficacy. Using an analog of the clinical-stage anti-CD70 antibody ARGX-110 as a reference, we screened a phage display library from immunized mice and identified high-affinity anti-CD70 antibodies, which were then used to construct a panel of second-generation CARs. Functional characterization identified a lead candidate, A174-CAR-T, with high CAR expression, strong in vitro antitumor activity, and low fratricide. We further humanized its single-chain variable fragment to generate A174-hu1-CAR. Compared with the parental construct, A174-hu1-CAR-T cells exhibited enhanced expansion and markedly reduced surface expression of CD70, consistent with improved cis-masking (i.e., surface shielding on the same cell). Molecular docking and surface electrostatic potential analyses suggested that humanization optimized the scFv-CD70 binding interface, which together with increased CAR surface expression contributed to the enhanced masking and reduced fratricide. Functionally, A174-hu1-CAR-T cells maintained potent cytotoxicity and showed enrichment of proliferative and central memory T-cell subsets. In xenograft models, A174-hu1-CAR-T infusion demonstrated potent antitumor efficacy against both AML and RCC, with a favorable safety profile. Overall, we developed a humanized CD70-targeted CAR-T cell therapy, A174-hu1-CAR-T, with reduced fratricide and potent antitumor activity, providing a preclinical foundation to support further translational development.