CAR-T Cell Therapy for Solid Tumors

Background: Chimeric antigen receptor (CAR)-modified T cells have shown remarkable results for the treatment of selected hematological malignancies, but recapitulating these results in solid cancers has been a major challenge. In this review, we discuss lessons learned from recent clinical trials, mechanisms of tumor immune evasion in solid cancers and strategies to alleviate these effects through advanced engineering strategies to augment the efficacy of CAR-T cell products. Summary: Despite early signs of clinical efficacy, CAR-T cells have repeatedly failed to achieve curative responses in solid cancers. While a major bottleneck remains the availability of tumor-specific antigens, recent studies suggest that conventional CAR-T cell products are not sufficiently well equipped to deal with the challenges encountered in the context of solid cancers. Various approaches to augment the potency and clinical efficacy of CAR-T cells are currently being evaluated, but the majority is yet to reach clinical trials. Moving forward, promising approaches include the use of next-generation CAR-T cell products, targeting physical barriers or cellular components within the tumor microenvironment (TME), and leveraging advanced engineering strategies to shield immune cells from the TME. These techniques aim to address current challenges and significantly improve the effectiveness of CAR-T cell therapies in treating solid tumors. Key Messages: Extensive research efforts have been made to understand the underlying mechanisms impeding curative treatment outcomes for CAR-T cell therapy in solid tumors. Early clinical trials, predominantly using second-generation CAR-T cell products, have shown promising signs of early clinical efficacy in the absence of consistent curative effects. Based on these data, it has become apparent that strategies to augment the efficacy of CAR-T cell therapy need to be implemented. Various approaches are currently being developed and are expected to enter clinical trials in the near future.