LB1141 Anti-mouse CX3CL1 monoclonal antibody therapy in mouse models of systemic sclerosis

We previously reported that the expression of CX3CL1 and its receptor, CX3CR1 was increased in patients with systemic sclerosis (SSc). In this study, we assessed the preclinical efficacy of an anti-CX3CL1 monoclonal antibody (mAb) in SSc. Cultured human dermal fibroblasts were used to evaluate the direct effect of anti-CX3CL1mAb on fibroblasts. In addition, bleomycin and growth factor-induced SSc models were used to investigate the effect of anti-CX3CL1mAb on leukocyte infiltration, collagen deposition, and vascular damage in the skin. Anti-CX3CL1mAb treatment inhibited Smad3 phosphorylation and expression of collagen I and fibronectin 1 in dermal fibroblasts stimulated with TGF-β1. In the bleomycin model, daily subcutaneous bleomycin injection increased serum and lesional CX3CL1. Administration of anti-CX3CL1mAb or CX3CR1 deficiency significantly reduced the skin inflammation, fibrosis, and vascular injury caused by bleomycin. Injection of bleomycin induced expression of phosphorylated Smad3 and TGF-β1 in the skin, which was inhibited by anti-CX3CL1mAb. Furthermore, the dermal infiltration of CX3CR1+ cells, macrophages (inflammatory and M2-like subsets), and CD3+ cells decreased following anti-CX3CL1mAb therapy. In the second model, anti-mCX3CL1mAb significantly diminished the skin fibrosis induced by serial subcutaneous injection of transforming growth factor-β and connective tissue growth factor. No apparent side effects of anti-CX3CL1mAb were detected in either model. Blockade of the CX3CL1-CX3CR1 axis can efficiently ameliorate the fibrosis and vascular injury occurring subsequent to skin inflammation in SSc mouse models. Anti-CX3CL1mAb therapy could be a novel approach for inflammation-driven fibrotic skin disorders such as SSc.