[Novel CD6-targeted CAR-T cell therapy for T-cell acute lymphoblastic leukemia: a safe and efficient strategy to prevent fratricide through gene editing].

Objective: To explore a novel strategy that addresses the dual challenges of fratricide and on-target off-tumor toxicity in current chimeric antigen receptor T-cell (CAR-T) therapy for T-cell acute lymphoblastic leukemia (T-ALL) and to develop a safe and efficacious anti-T-ALL CAR-T product by identifying a new target and compatible gene-editing approach. Methods: Public single-cell RNA sequencing (scRNA-seq) datasets were utilized to analyze bone marrow cells extracted from patients with T-ALL and healthy donors, evaluating the differential expression profiles of CD6 and CD7. In investigating the endogenous role of CD6 in CAR-T cells, the CRISPR/Cas9 RNP system was first employed in a CD19 CAR-T model to evaluate the impact of CD6 knockout on the phenotype and activation status of CAR-T cells. Subsequently, CD6-knockout, CD6-targeted CAR-T cells (6KO-6CAR) were constructed, and their functional activities were evaluated. Results: scRNA-seq analysis revealed that CD6 is broadly expressed in T-ALL. Compared with the traditional target CD7, which is also expressed in a subset of normal hematopoietic stem/progenitor cells and myeloid cells, CD6 exhibits a more restricted expression profile, exhibiting superior safety characteristics. Studies on the CD19 CAR-T model indicated that CD6 knockout enables CAR-T cells to maintain a superior functional state: their baseline activation level (CD25 expression) was reduced (P<0.05) while generating a higher proportion of TNF-α(+)IFN-γ(+) cells (P<0.05) upon antigen stimulation. The further constructed 6KO-6CAR cells exhibited potent specific activation (significantly upregulated CD107a expression level, all P<0.001) and cytotoxicity (all P<0.05) against multiple CD6(+) T-ALL cell lines (MOLT-4, CCRF-CEM, and Jurkat) in vitro. Conclusion: CD6 is a novel therapeutic target for T-ALL with high coverage and a favorable safety profile, and knocking out endogenous CD6 globally optimizes the intrinsic functional state of CAR-T cells. Constructing 6KO-6CAR based on the CRISPR/Cas9 technology addresses fratricide in CAR-T cells while enhancing their antitumor functionality, thereby providing a novel immunotherapy regimen with safety and clinical translational potential for relapsed/refractory T-ALL.