Sclerotic graft-vs-host disease shares dysregulated gene expression with scleroderma that can be targeted with epiregulin inhibition

Summary: Abstract Body: Chronic graft-versus-host-disease (cGvHD) causes skin fibrosis in more than half of affected patients that is similar to systemic sclerosis (SSc), suggesting similar pathologic processes. To understand common signaling mechanisms, we compared differentially expressed genes (DEGs) in skin biopsies of patients with sclerotic GvHD to SSc and healthy controls by scRNA-Seq. Among most cell types, sclerotic GvHD and SSc shared similar proportions of overlapping and unique DEGs. SSc showed elevated number of unique DEGs by endothelial cells, consistent with its well-established vasculopathy. Remarkably, sclerotic GvHD showed strong upregulation of gene ontology terms associated with DC3 dendritic cells including TNFA, type I interferon, and IL-1 signaling (p<10-7-10-11), and enrichment by ligand-receptor analysis of the DC3 derived EGFR ligand epiregulin (EREG, p=0.014) which we previously demonstrated to be pathogenic in SSc. To understand EREG inhibition as a therapeutic strategy in sclerotic GvHD, we generated a high affinity fully human EREG neutralizing antibody (NAb, KD 5x10-11, IC50 2.5 nM). Our fully human EREG NAb was not cross reactive with mouse EREG or other EGFR ligands. We therefore developed a human skin explant system in which viable human skin biopsies could be maintained in culture. Skin explants retained a full repertoire of immune cells, including CD4 and CD8 T cells, macrophages, and dendritic cells. Using the skin explant model with sclerotic GvHD skin biopsies, we found that the human EREG NAb reduced production of key fibrotic and inflammatory disease biomarkers MCP1 (p<0.0001), TNC (p<0.001), TIMP1 (p<0.01), and FN1 (p=0.06) by patient skin. Thus, sclerotic GvHD and SSc share pathways activated by DC3 dendritic cells that can be targeted therapeutically with an EREG neutralizing antibody. Ian D. Odell¹, Nathan M. Newton¹, Anahi V. Odell¹, Michael Girardi¹, Richard Flavell^{1, 2} 1. Yale University School of Medicine, New Haven, CT, United States. 2. Howard Hughes Medical Institute, Chevy Chase, MD, United States. Translational Studies: Preclinical