T cell engagers (TCEs) are antibody-based, bispecific or multi-specific constructs that can reprogramme T cells to eliminate target cells expressing a defined surface antigen. Originally developed for cancer therapy, TCEs are now being investigated for the treatment of autoimmune diseases, with promising initial results. The interest in using TCEs for autoimmune diseases is rapidly growing given their comparable potency with cellular therapies, combined with the advantages of biologics, including ease of manufacturing, off-the-shelf availability, better safety and more convenient delivery. Here we review the history of TCEs, focus on distinct aspects of the mechanism of action of TCEs and explain design principles. We also discuss key challenges for future TCE development in autoimmunity, including enhanced safety, high convenience and complete target cell elimination. Finally, we provide an overview of the preclinical and clinical development landscape and give an outlook on next-generation TCEs that are optimized to treat a wide variety of autoimmune diseases.
