Antigen-binding affinity is a key determinant of the durable antitumor activity of CD5 CAR-T cells.

T cell fratricide in T cell antigen-targeted chimeric antigen receptor (CAR)-T cell therapies remains a critical barrier to achieving optimal antitumor efficacy. To address this challenge, we explored modulation of antigen-binding affinity as a simple yet effective strategy to mitigate fratricide. To this end, we aimed to develop low-affinity CD5-specific CAR-T cells and to test the hypothesis that low-affinity CD5 CAR-T cells can evade T cell fratricide, thereby alleviating T cell exhaustion and enhancing sustained antitumor activity. Our results demonstrate that CD5 CAR-T cells engineered with low-affinity monoclonal antibodies exhibit significantly reduced fratricide and diminished T cell exhaustion in the infusion product compared to high-affinity counterparts such as the standard H65 and A2 clones, which is assumed to correlate with improved long-term antitumor responses. These findings establish antigen-binding affinity modulation as a promising alternative to extensive gene editing approaches, potentially simplifying CD5 CAR-T cell manufacturing while improving therapeutic outcomes.