Systemic sclerosis (SSc) is a rare systemic autoimmune connective tissue-disease characterized by fibrosis, inflammation, and vasculopathy. SSc is responsible for skin fibrosis that can either be limited or diffuse. The latter phenotype of the disease is commonly associated with visceral involvement and therefore similar to graft versus host disease (GvHD) reaction. It can be life threatening in case of pulmonary or cardiovascular involvement. Nonetheless SSc remains a severe disease responsible for important disability and a poor quality of life.~There is a growing body of evidence that supports the implication of the JAK-STAT tyrosine kinases pathway in the activation of fibroblasts of patients with SSc. A genetic polymorphism of STAT4 was found to be associated with the diffuse form of the disease and inhibition of STAT4 gene is associated with a decrease in TGF-ß and IL-6 cytokines activation, which are two major cytokines implicated in SSc pathogenesis. Recently, Pedroza et al. confirmed the implication of STAT3 in skin fibrosis mechanisms. Indeed, the authors showed an enhanced activation of STAT3 and demonstrated in vivo that the inhibition of STAT3 phosphorylation prevented skin fibrosis in a murine model of SSc. These data were confirmed by a work of Zhang et al. who showed that the inhibition of JAK1 was also needed to prevent skin and lung fibrosis. Altogether these works confirmed the implication of the JAK pathway in fibrosis mechanism.~Itacitinib is a Janus kinase inhibitor that specifically targets JAK1 and decreases STAT3 phosphorylation. Itacitinib was shown to efficiently treat patients with myelofibrosis, rheumatoid arthritis, and chronic plaque psoriasis. Very interestingly, itacitinib efficacy has also been reported in patients with acute GvHD. Altogether these data and studies reinforced the investigator's working hypothesis.~The efficacy and safety of this proposal must be tested.
The purpose of this study is to determine whether itacitinib is safe and effective in the treatment of systemic sclerosis in adults.