Sclerotic GVHD and Scleroderma Share Dysregulated Gene Expression that is Ameliorated by EREG Therapeutic Antibody.

Immune driven fibrotic skin diseases including scleroderma/systemic sclerosis (SSc) and chronic graft-versus-host-disease (cGvHD) cause skin stiffening that has major impact on patient quality of life and associated patient mortality. Therapies to improve sclerotic skin resulting from these diseases are largely ineffective. We previously showed that EREG, a DC3 dendritic cell-derived EGFR ligand, is elevated in the skin and lung of patients with SSc and required for maintenance of skin fibrosis. Here, we developed a fully human anti-EREG neutralizing antibody that has both high affinity and specificity. We found this therapeutic antibody to be functional and safe in vivo using human EREG knock-in mice. To understand the antifibrotic mechanism of targeting EREG, we aligned skin single-cell transcriptomic profiles of SSc, morphea (localized scleroderma) and SclGvHD with disease biomarkers. EREG expression in the skin was elevated in all three fibrotic diseases and a driver of TNC production by myofibroblasts in all three fibrotic diseases. TNC is a pro-inflammatory extracellular glycoprotein that functions as an endogenous TLR4 ligand which induces expression of TLR4 target genes CCL2 and IL6. Examination of skin explants from patients with active SclGvHD treated with anti-EREG therapeutic antibody by spatial transcriptomics demonstrated upregulation of matrix degradation by increased MMP and decreased TIMP1 expression. Protein measurements showed reduced secretion of EREG targets TNC, CCL2, and TIMP1 in all patients, and type I collagen and FN1 in 3/4 patients. Thus, sclerotic skin treated with the anti-EREG therapeutic antibody reduced inflammatory and fibrosis biomarkers associated with EGFR and TLR4 signaling.