CAR-T cells in solid tumors: Challenges and breakthroughs

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment of hematologic malignancies, but its efficacy in solid tumors is limited by several challenges. Key obstacles include insufficient CAR-T cell trafficking to tumors, limited expansion and persistence, tumor relapse due to antigen loss or heterogeneity, and an immunosuppressive tumor microenvironment (TME) that dampens CAR-T cell functions. In this review, we discuss insights from recent successful clinical trials in advanced solid tumors and highlight groundbreaking strategies integrating synthetic biology and gene engineering to enhance CAR-T cell fitness, potency, and persistence, activate host immunity, reprogram the TME, and enable multi-antigen targeting. We examine strengths and weaknesses of current preclinical models for assessing the efficacy and safety of CAR-T cell therapies, including human xenografts in immunodeficient mice and humanized or syngeneic models. The array of cutting-edge approaches employed in next-generation CAR-T cell therapies is expected to transform the treatment landscape of solid tumors.