Primary Objective:

To evaluate, in comparison with placebo, the efficacy of SAR156597 administered subcutaneously for 24 weeks on skin fibrosis in participants with diffuse cutaneous systemic sclerosis (dcSSc).

Secondary Objectives:

• To evaluate the efficacy of SAR156597 compared to placebo on physical/functional disability in participants with dcSSc.
• To evaluate the efficacy of SAR156597 compared to placebo on respiratory function of participants with dcSSc.
• To evaluate the safety profile of SAR156597 compared to placebo in participants with dcSSc.
• To evaluate the potential for immunogenicity (anti-drug antibodies response) of SAR156597 in participants with dcSSc.
• To evaluate the pharmacokinetics (trough plasma concentrations) of SAR156597 administered subcutaneously for 24 weeks.

The total study duration per participant was 39 weeks; consisting of a 4-week screening, a 24-week of study treatment period, and an 11-week follow-up with no study drug treatment.

Inclusion criteria :

• Systemic Sclerosis (SSc) according to the American College of Rheumatology/The European League against Rheumatism (ACR/EULAR) 2013 criteria.
• Diffused cutaneous form of SSc according to Leroy's criteria.
• Able and willing to sign the written informed consent form with comprehension of its contents and complied with the requirements of the study protocol.

Exclusion criteria:

• Aged less than (<) 18 years of age.
• Disease duration for greater than (>) 36 months from time of first non-Raynaud's phenomenon manifestation.
• Modified Rodnan Skin Score <10 or >35 at screening and baseline visits.
• History of vasculitis, active or in remission.
• Diagnosis of connective tissue diseases (other than SSc) or overlap syndrome (eg, polymyositis/scleroderma).
• Positive Human Immunodeficiency Virus (HIV) serology or a known history of HIV infection, active or in remission.
• Abnormal hepatitis B and/or hepatitis C tests indicative of active or chronic infection:
• Abnormal Hepatitis B tests: Positive hepatitis B surface antigen (HBsAg) OR positive total hepatitis B core antibody (HBcAb) with negative hepatitis B surface antibody (HBsAb) OR positive total HBcAb with positive HBsAb and presence of hepatitis B virus deoxyribonucleic acid.
• Abnormal Hepatitis C tests: Positive anti-hepatitis C virus antibody (HCV Ab) and positive HCV ribonucleic acid.
• Positive or 2 confirmed indeterminate Quantiferon-tuberculosis Gold tests at screening (regardless of prior treatment status).
• Serious infection (eg, pneumonia, pyelonephritis) within 4 weeks of screening, infection requiring hospitalization or intravenous antibiotics within 4 weeks of screening or chronic bacterial infection (eg, osteomyelitis).
• History of anaphylaxis to any biologic therapy.
• Evidence of any clinically significant, severe or unstable, acute or chronically progressive, uncontrolled infection or medical condition (eg, cerebral, cardiac, pulmonary, renal, hepatic, gastrointestinal or neurologic other than SSc or SSc-interstitial lung disease) or previous, active or pending surgical disorder, or any condition that may affect participant safety in the judgment of the Investigator.
• At screening, the percent (%) predicted forced vital capacity was less than or equal to (<=75) % and % predicted carbon monoxide diffusing lung capacity after hemoglobin correction is <=40%.
• History of heart failure (including acutely decompensated in the setting of preserved ejection fraction), left ventricular ejection fraction <= 45%, coronary artery disease, angina, myocardial infarction, ischemic cardiomyopathy and/or hypertrophic cardiomyopathy.
• Any prior history of malignancy or active malignancy, including lymphoproliferative diseases (except successfully-treated carcinoma in-situ of the cervix, non-metastatic squamous cell carcinoma or basal cell carcinoma of the skin) within 5 years prior to baseline.
• Ischemic electrocardiogram (ECG) changes (except those not supported by the findings of a left heart catheterization performed in the last year) and/or other clinically significant ECG findings. (All abnormal ECG finding were reviewed and confirmed by a local cardiologist).
• High dose steroids (>10 mg/day prednisolone equivalent); or change in steroid dose within 4 weeks prior to randomization (or baseline visit); or expected changes during the course of the study.
• Previous treatment with rituximab within 12 months prior to screening.
• Previous treatment with bone marrow transplantation, total lymphoid irradiation or ablative ultra-high dose cyclophosphamide.
• Treatment with high dose immunosuppressive drug (eg, cyclophosphamide >1 mg/kilogram (kg) oral/day or >750 mg intravenous (IV)/month; azathioprine >100 mg/day; methotrexate >15 mg/week; mycophenolate mofetil >2 gram (g)/day) within 3 months of screening or change in dose within 4 weeks prior to randomization (or baseline visit); or expected changes in dose during the course of the study.
• Treatment with etanercept, cyclosporine A, IV immunoglobulin, rapamycin, D-penicillamine, tyrosine kinase inhibitors within 4 weeks of screening or antithymocyte globulin within 6 months of screening.
• Treatment with infliximab, certolizumab, golimumab, abatacept, or adalimumab, tocilizumab within 8 weeks of screening or anakinra within 1 week of screening.
• Treatment with any investigational drug within 1 month of screening, or 5 half-lives, if known (whichever was longer).
• Abnormal laboratory tests at screening:
• Alanine transaminase or aspartate transaminase >2 times upper limit of normal range;
• Hemoglobin <11 g/100 milliliter (mL) for male and <10 g/100 mL for female;
• Neutrophils <1500/mm^3 (except <1000/mm^3 for those of African descent);
• Platelets <100 000/mm^3;
• Creatinine greater than or equal to (>=)150 micromole/Liter (mcgmol/L).
• Current history of substance and/or alcohol abuse.
• Any condition or circumstance that would preclude the participant from following and completing protocol requirements, in the opinion of the Investigator.
• Pregnant or breastfeeding woman.
• Women who were of childbearing potential not protected by highly-effective contraceptive method(s) of birth control, and/or who were unwilling or unable to be tested for pregnancy.

The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org