Adoptive cell therapies in solid tumors: current clinical landscape, challenges, and future directions

Adoptive cell therapy (ACT) has emerged as a transformative strategy in cancer immunotherapy, offering durable clinical benefit in hematologic malignancies and expanding therapeutic potential in solid tumors. However, the translation of ACT to solid malignancies remains constrained by biological, immunological, and logistical challenges. This narrative review provides an evidence based overview of the current clinical landscape of ACT in solid tumors, with a focus on chimeric antigen receptor T cell (CAR-T), tumor-infiltrating lymphocyte (TIL), and T cell receptor-engineered T cell (TCR-T) therapies. We summarize recent clinical trial outcomes, highlight tumor-specific antigen targets, and examine key determinants of therapeutic efficacy across major solid tumor types. The review discusses central obstacles limiting ACT success in solid tumors, including antigen heterogeneity, immune evasion, inadequate T cell trafficking, limited persistence, and functional exhaustion within the immunosuppressive tumor microenvironment. Mechanisms driving treatment resistance, on-target off-tumor toxicity, and immune-related adverse events such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome are critically evaluated. We further examine evolving strategies designed to overcome these barriers, including multi-antigen targeting, armored and logic-gated CAR designs, metabolic and cytokine engineering, locoregional delivery approaches, and next-generation manufacturing platforms incorporating allogeneic and gene-edited products. In parallel, the role of biomarkers, tumor microenvironment profiling, and personalized treatment selection is explored as a means to optimize patient stratification and enhance therapeutic outcomes. Advances in translational research, combination immunotherapy, and precision immuno-oncology are positioned as key drivers of the next phase of ACT development. By integrating mechanistic insights with emerging clinical evidence, this review outlines the progress, limitations, and future directions of ACT in solid tumors. It aims to provide a forward-looking framework to guide ongoing research, clinical trial design, and the rational implementation of adoptive cellular immunotherapies in solid malignancies.