A Targeted Approach to Treat Immunotherapy-Induced Myocarditis with CXCR3 Blockade - PROJECT SUMMARY/ABSTRACT Immune checkpoint inhibitors (ICIs) are cancer therapeutics that unleash T-cell cytotoxicity against tumors. While effective for up to 50% of cancer patients, ICIs can cause ICI myocarditis (ICIM), pathologic inflammation of the heart—a life-threatening side effect leading to arrhythmias, heart failure and death. Despite a high case fatality rate, there are no effective ICIM therapies; thus, there is an enormous unmet clinical need for mitigating therapies. Our group has defined immunologic drivers in ICIM using pre-clinical and patient samples. Using novel single- cell multi-omics, we found that crosstalk between T-cells and macrophages in the heart is critical for ICIM development, bringing forth a new therapeutic opportunity. This proposal is to develop a mechanism-based therapy for ICIM blocking crosstalk between macrophages expressing chemokines CXCL9/10 (CXCL9/10+MP) and antigen-specific T-cells expressing the chemokine receptor CXCR3 (CXCR3hiCD8 T-cells) in the heart. Our previous work has shown that CXCR3 blockade mitigates ICIM in a non-tumor mouse model. Since current ICIM models do not account for tumor, we have now created more realistic tumor ICIM models by inoculating C57/BL6J mice with B16F1 melanoma/MC38 colorectal tumors. Our preliminary data in these models demonstrate mitigation of ICIM with CXCR3 blockade while maintaining ICI tumor control. Through drug screening, we have discovered drug-like small molecule CXCR3 inhibitors which will increase translational opportunities. In Aim 1, we will test the hypothesis that ICIM involves a cardiac infiltration of CXCL9/10+MP/antigen-specific CXCR3hiCD8+ T-cells in ICIM distinct from tumor associated macrophages (TAMs)/antigen-specific CD8 tumor infiltrating lymphocytes (CD8 TILs) present in tumors. We will validate our findings in our tumor mouse models and patient samples. In Aim 2, we will perform CXCR3 blockade in the mouse tumor models, assessing the effect of blockade on heart/tumor phenotype and immune profile using single-cell multi-omics. In Aim 3, we will test the hypothesis that CXCR3 blockade reduces migration/cytotoxicity of cardiac CXCR3hiCD8 T-cells but not CD8 TILs. We will determine functional effects of CXCR3 blockade on cardiac CXCR3hiCD8 T-cell/TIL ex vivo with transwell assays and co-cultures with cardiomyocytes/tumor cells. These studies will provide critical and timely data on CXCR3 blockade as a novel targeted therapy for ICI myocarditis in a clinical space where treatments are urgently needed.
