Characterization of a novel chimeric autoantigen receptor (CAAR) treatment for Graves' disease - Program Director/Principal Investigator (Last, First, Middle): Weber, K. Scott Project Summary Graves’ Disease (GD) is the fourth most common autoimmune disease in the United States, affecting ~6.5 million people, that primarily results in hyperthyroidism. The immunopathogenesis of the disease is initiated by autoreactive B cells which secrete antibodies that bind to the thyroid stimulating hormone receptor (TSHR). These anti-TSHR autoantibodies (TRAbs) are the critical cause of disease. They bind to TSHR on thyroid cells, causing chronic stimulation and overproduction of thyroid hormones. Currently, there are no treatments available to address the disease causing mechanism of GD, the TRAb producing B cells. The goal of this research is to apply the concept of chimeric antigen receptor (CAR) T cell therapy to the development of a novel and potentially curative treatment for GD. This will be done by generating a chimeric autoantigen receptor (CAAR), which replaces the binding domain of a standard CAR with a fragment of the TSHR. The TSHR fragment acts as bait for autoreactive B cells, because the B cell receptors (BCR) on their surface bind to TSHR just as soluble TRAbs do. We have engineered TSHR CAAR T cells, and our preliminary data show that the CAAR T cells bind to anti-TSHR Abs and B cell receptors, activate significantly, and can specifically eliminate anti-TSHR B cells, but not other B cells. We will further characterize these GD CAAR T cells by performing the following aims. 1) We will perform several cytotoxicity assays to determine the efficacy of our CAAR T cells at eliminating anti-TSHR B cells while not harming other B cells. Flow cytometry based cytotoxicity, proliferation, cytokine secretion assays, and a direct cytotoxicity assay will be performed. 2) We will evaluate the influence of soluble TRAbs in GD patients that will likely bind to our CAAR T cells, which could have an inhibitory or activating effect. We will perform cytotoxicity experiments in the presence of physiologically relevant levels of commercially available TRAbs and GD patient serum. We will also evaluate cytotoxicity in the presence of thyroid stimulating hormone to determine its possible effect on the CAAR T cells. 3) We will develop a bispecific LINK CAAR to further increase the safety and specificity of the treatment, by requiring binding to anti-TSHR BCR/Ab and a B cell marker, CD19, to initiate the CAAR T cell cytotoxicity. These LINK CAAR T cells will be compared to our original CAAR T cells for their efficiency, specificity, and ability to activate only on target. Thus, this project applies concepts of CAR T cell therapy to the development of a novel and potentially curative immunotherapy treatment for Graves’ disease. Project Summary
