Bifunctional Cysteine-Engineered CAR‑T Cells Enable Thiol-Mediated Targeting to Overcome Antigen Escape in B Cell...

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of hematologic malignancies; however, durable remissions remain limited due to antigen-negative cancer relapse, where tumor cells downregulate or lose the targeted antigen to evade immune recognition. To address this challenge, we developed cysteine-engineered CAR (CysCAR) T cells that redirect T cells to target cancer cells based on extracellular redox imbalances and the altered thiol/disulfide ratios, a marker we identified on B cell lymphomas. Here, we show that CysCAR-T cells, engineered with different cysteine-modified antibody fragments, exhibit a potent and specific cytotoxicity in vitro across various B cell lymphoma (BCL) subtypes, even in antigen escape models. Moreover, by integrating cysteine engineering with clinically used anti-CD19 CAR-T cells, we enabled simultaneous targeting of CD19 and altered redox states on BCL, potentially reducing the risk of antigen escape. In a pilot in vivo study, these bifunctional CD19-CysCAR-T cells suppressed tumor growth and prolonged survival of BCL-bearing mice without inducing systemic toxicity. Given that aberrant exofacial redox states are a hallmark of multiple cancers, our findings suggest a promising strategy to enhance the efficacy of anti-CD19 CAR-T cell therapy, overcome antigen escape, and reduce tumor relapse in BCL, with potential applicability to other malignancies.