Chimeric Antigen Receptor T‐Cell Therapy: More Than an Anti‐Cancer Drug

Initially, chimeric antigen receptor (CAR) T-cell therapy was developed to eliminate malignant B cells in haematological B-cell malignancies by targeting CD19 and B-cell maturation antigen. This approach achieved notable success, resulting in (malignant) B-cell depletion and inducing clinical remission in cancer patients. The scope of CAR T-cell therapy has since expanded to various other applications. Recently, CD19-directed CAR T cells have shown promising results in treating B-cell-mediated autoimmune diseases, with patients experiencing long-lasting symptom cessation. Despite these advancements, the unselective targeting of both pathogenic and protective B cells calls for precise immunotherapies capable of selectively removing pathogenic B cells. Therefore, antigen-specific CARs were designed to specifically interact with and deplete subpopulations of target cells expressing the target antigens. Subsequently, modified CARs were introduced by incorporating autoantigens into the sequence, which allowed antigen-specific B cells to bind to CAR T cells. Additionally, antigen-specific CAR T cells have been exploited to treat viral infections. Moreover, CAR technology was expanded to regulatory T cells (Tregs), where CARs can be adopted to induce a tolerogenic environment in target tissues, offering new possibilities in autoimmune diseases, as well as prevention of graft-versus-host disease in haematopoietic stem cell transplantation and transplant rejection in the setting of solid organ transplantation. Although CAR T cells and CAR Tregs are promising and broadly explored, safety issues must be addressed and possible solutions thoroughly investigated. This review outlines the broad potential of CAR-based therapies in autoimmunity, virology and transplantation while addressing the need for solutions to current safety issues.