Safety and Efficacy of Itacitinib in Adults With Systemic Sclerosis

Inclusion Criteria: * Adult patient (≥18 years old) * Patient with a diagnosis of diffuse SSc, as defined by the American College of Rheumatology / EULAR 2013 criteria, * Patient with a diffuse SSc, according to Leroy and Medsger dichotomy * Patient with a SSc disease duration of less than 36 months (defined as time from first non-Raynaud phenomenon manifestation) or with an active SSc disease, as defined by EUSTAR disease activity score, * Patient with a modified Rodnan skin score (mRSS) ≥ 10 and ≤ 35 units at screening, * Negative pregnancy test for woman of childbearing potential, woman of childbearing potential should have reliable contraception for the 12 months' duration of the study, * Patient able to give written informed consent prior to participation in the study, * Affiliation to a social security scheme (profit or being entitled) * If patients receive mycophenolate or methotrexate for SSc, these need to be on stable dose as follows: * Mycophenolate mofetil/sodium: stable dose for at least 2 months prior to randomisation * Methotrexate: stable dose and route of administration for at least 2 months prior to randomisation Exclusion Criteria: * Previous treatment with itacitinib or a Janus kinase (JAK) inhibitor, * Contra-indications to itacitinib or Janus kinase inhibitor, * Failure to sign the informed consent or unable to consent * Patient participating in another investigational therapeutic study, * Acute or chronic active infections, including HBV, HCV, HIV, * Patient with other uncontrolled diseases, including drug or alcohol abuse, severe psychiatric diseases, that could interfere with participation in the trial according to the protocol, * Patient suspected not to be observant to the proposed treatments, * Patient who have white blood cell count ≤ 4,000/mm3, * Patient who have platelet count ≤ 100,000/mm3, * Patients who have ALT or AST level greater that 3 times the upper limit of normal, * Patient who have triglyceride level greater than 5g/L * Pregnant or breastfeeding woman, * Protected adults (including individual under guardianship by court order), * Patient receiving or having received cyclophosphamide or rituximab within the last three months (possible inclusion beyond 3 months), * Patient receiving or having received a biotherapy (anti-TNF, abatacept or tocilizumab) in the last 3 months (possible inclusion beyond 3 months) * Patient with Systemic Lupus, or Sjögren's syndrome with systemic manifestations justifying immunosuppressive therapy * Atherosclerotic cardiovascular disease as defined by a history of myocardial infarction, ischaemic stroke, or peripheral artery thrombosis * Anti-phospholipid syndrome