Genetic Engineering in CAR T Cells for Solid Tumors: Current State, Barriers and Future Developments

Chimeric antigen receptor (CAR) T cell therapy has revolutionized treatment for hematological malignancies, yet translating this success to solid tumors remains challenging. Major obstacles include antigen heterogeneity, on-target off-tumor toxicity, limited infiltration and persistence, and the immunosuppressive tumor microenvironment (TME). The present review discusses recent engineering strategies designed to overcome these barriers. Innovations such as affinity-tuned and logic-gated CARs improve specificity and safety, while multi-antigen targeting helps address tumor heterogeneity by avoiding antigen escape. Gene-editing approaches enhance CAR T cell fitness by promoting memory phenotypes, metabolic resilience, and resistance to inhibitory signals imposed by the immunosuppressive TME. Additional modifications improve trafficking, enable extracellular matrix degradation, and reprogram CAR T cells to withstand the hostile conditions of the TME. Together, these advances reflect a growing shift toward rational CAR design and synthetic immunology, with the goal of achieving durable and safe responses in solid tumors. Early clinical trials show promise, and continued translational efforts will be key to unlocking the full therapeutic potential of CAR T cells in this setting.