Chimeric Antigen Receptor Therapy: How Are We Driving in Solid Tumors?

Immune effector cell (IEC) therapy is emerging as a promising approach in the field of cancer immunotherapy. Clinical IEC trials, predominantly using chimeric antigen receptor (CAR) T cells, have shown excellent responses in CD19 B cell malignancies and multiple myeloma. In solid tumors, preclinical data are encouraging, but clinical data are in their infancy, and there are challenges in using CAR T therapy in this setting, including (1) on-target off-tumor toxicity, (2) optimal target identification, (3) effective trafficking into bulky tumor tissue, and (4) resistance to tumor immune evasion mechanisms. Novel techniques and modifications are being explored in both the preclinical and clinical settings, aiming to improve treatment efficacy and address the aforementioned obstacles to successful CAR T therapy in solid tumors. Here we review these challenges in a clinically oriented approach and summarize published clinical trials using CAR T therapy in a variety of solid tumors.