Primary Objective:

To evaluate the immunogenicity of sarilumab administered as monotherapy.

Secondary Objectives:

• To evaluate the other safety aspects of sarilumab administered as monotherapy.
• To assess the exposure of sarilumab administered as monotherapy.

Total study duration was up to 34 weeks: Up to 4-week screening period, 24-week open-label treatment phase, 6-week post-treatment observation. After completion of the treatment phase of this study, participants were eligible to enter a long term safety study (LTS11210 - SARIL-RA-EXTEND) for continuous treatment with sarilumab (SAR153191 [REGN88]).

Inclusion criteria:

• Diagnosis of rheumatoid arthritis (RA) ≥ 3 months.
• Moderately to severely active rheumatoid arthritis.
• Participants who per investigator judgment were incomplete responders to at least 12 weeks of an adequate dose of continuous treatment with or who were intolerant of one or a combination of non-biologic disease modifying anti-rheumatic drugs (DMARDs).

Exclusion criteria:

• Participants < 18 years of age.
• Past history of, or current, autoimmune or inflammatory systemic or localized joint disease(s) other than RA.
• History of juvenile idiopathic arthritis or arthritis onset prior to age 16.
• Severe active systemic RA, including but not limited to vasculitis, pulmonary fibrosis, and/or Felty's syndrome.
• Prior treatment with any biologic anti-interleukin 6 (IL-6) or IL-6 receptor (IL-6R) antagonist therapies.
• Treatment with prednisone > 10 mg or equivalent per day, or change in dosage within 4 weeks prior to randomization.
• New treatment with or dose-adjustment of on-going nonsteroidal anti-inflammatory drug (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors within 4 weeks prior to randomization, except for the use of low-dose acetylsalicylic acid for cardiovascular diseases.
• Use of parenteral glucocorticoids or intra-articular glucocorticoids injection within 4 weeks prior to randomization.
• Prior treatment with a Janus kinase (JAK) inhibitor (tofacitinib).
• New treatment or dose-adjustment to on-going medication for dyslipidemia, such as statin, within 6 weeks prior to randomization.
• Participation in any clinical research study evaluating another investigational drug or therapy within 5 half-lives or 60 days of first dose of study drug administration, whichever is longer.
• Participants with a history of malignancy other than adequately-treated carcinoma in-situ of the cervix, non-metastatic squamous cell or basal cell carcinoma of the skin, within 5 years prior to the randomization visit. Non-malignant lymphoproliferative disorders are also excluded.
• Participants with active tuberculosis or untreated latent tuberculosis infection.
• Pregnant or breast feeding women.

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