Evaluation of the Efficacy and Safety of Two Dosing Regimens of Olokizumab (OKZ), Compared to Placebo, in Subjects With Rheumatoid Arthritis (RA) Who Were Taking an Existing Medication Called a Tumour Necrosis Factor Alpha Inhibitor But Had Active Disease

Inclusion Criteria: Subjects may be enrolled in the study only if they meet all of the following criteria. * Subjects willing and able to sign informed consent * Subjects must have a diagnosis of adult onset RA classified by ACR/EULAR 2010 revised classification criteria for RA for at least 24 weeks prior to Screening. (If the subject was diagnosed according to ACR 1987 criteria previously, the Investigator may classify the subject per ACR 2010 retrospectively, using available source data.) * Treatment with oral, SC, or intramuscular (IM) MTX for at least 12 weeks prior to Screening at a dose of 15 to 25 mg/week (or ≥10 mg/week if there is documented intolerance to higher doses) * The dose and means of administering MTX must have been stable for at least 6 weeks prior to Screening. * Subjects must be willing to take folic acid or equivalent throughout the study. * Subjects must have moderately to severely active RA disease as defined by all of the following: * ≥6 tender joints (68 joint count) at Screening and baseline; and * ≥6 swollen joints (66 joint count) at Screening and baseline; and * C-reactive protein (CRP) above Upper limit of normal (ULN) at Screening based on the central laboratory results. * Subjects must have a documented inadequate response to treatment (i.e., TNFi failure) with ≥1 licensed TNFi following at least 12 weeks of therapy with that agent. Inadequate response to treatment is classified as either: * Primary failure: The absence of any documented clinically significant response; or * Secondary failure: Documented initial response with subsequent loss of that response or partial response Exclusion Criteria: * Diagnosis of any other inflammatory arthritis or systemic rheumatic disease (e.g., gout, psoriatic or reactive arthritis, Crohn's disease, Lyme disease, juvenile idiopathic arthritis, or systemic lupus erythematosus) (However, subjects may have secondary Sjogren's syndrome or hypothyroidism.) * Subjects who are Steinbrocker class IV functional capacity (incapacitated, largely or wholly bed-ridden or confined to a wheelchair, with little or no self-care) * Prior exposure to any licensed or investigational compound directly or indirectly targeting Interleukin (IL) 6 or IL 6R (including tofacitinib or other Janus kinases and spleen tyrosine kinase \[SYK\] inhibitors) * Prior treatment with cell depleting therapies including anti CD20 or investigational agents (e.g., CAMPATH, anti CD4, anti CD5, anti CD3, and anti CD19) with the exception of rituximab, which is allowed if it was discontinued at least 24 weeks prior to baseline (rituximab should not be discontinued to facilitate a subject's participation in the study, but should instead have been previously discontinued as part of a subject's medical management of RA). * Prior use of bDMARDs, within the following windows prior to baseline (bDMARDs should not be discontinued to facilitate a subject's participation in the study, but should instead have been previously discontinued as part of a subject's medical management of RA): 1. 4 weeks for etanercept and anakinra 2. 8 weeks for infliximab 3. 10 weeks for adalimumab, certolizumab, and golimumab 4. 12 weeks for abatacept * Use of parenteral and/or intra-articular glucocorticoids within 4 weeks prior to baseline * Use of oral glucocorticoids greater than 10 mg/day prednisone (or equivalent) or change in dosage within 2 weeks prior to baseline * Prior documented history of no response to hydroxychloroquine and sulfasalazine * Prior use of cDMARDs (other than MTX) within the following windows prior to baseline (cDMARDs should not be discontinued to facilitate a subject's participation in the study, but should instead have been previously discontinued as part of a subject's medical management of RA): 1. 4 weeks for sulfasalazine, azathioprine, cyclosporine, hydroxychloroquine, chloroquine, gold, penicillamine, minocycline, or doxycycline 2. 12 weeks for leflunomide unless the subject has completed the following elimination procedure at least 4 weeks prior to baseline: Cholestyramine at a dosage of 8 grams 3 times daily for at least 24 hours, or activated charcoal at a dosage of 50 grams 4 times daily for at least 24 hours 3. 24 weeks for cyclophosphamide * Vaccination with live vaccines in the 6 weeks prior to baseline or planned vaccination with live vaccines during the study * Participation in any other investigational drug study within 30 days or 5 times the terminal half-life of the investigational drug, whichever is longer, prior to baseline * Other treatments for RA (e.g., Prosorba Device/Column) within 6 months prior to baseline * Use of intra-articular hyaluronic acid injections within 4 weeks prior to baseline * Use of non steroidal anti inflammatory drugs (NSAIDs) on unstable dose or switching of NSAIDs within 2 weeks prior to baseline * Previous participation in this study (randomized) or another study of OKZ * Subjects with concurrent acute or chronic viral Hepatitis B or C infection as detected by blood tests at Screening (e.g., positive for hepatitis B surface antigen \[HBsAg\], total hepatitis B core antibody \[anti-HBc\], or hepatitis C virus antibody \[HCV Ab\]) a) subjects who are positive for hepatitis B surface antibodies (anti-HBs), but negative for HBsAg and anti-HBc, will be eligible. * Subjects with HIV infection * Subjects with: 1. Suspected or confirmed current active tuberculosis (TB) disease or a history of active TB disease. 2. Close contact (i.e., sharing the same household or other enclosed environment, such as a social gathering place, workplace, or facility, for extended periods during the day) with an individual with active TB within 1.5 years prior to Screening * Concurrent malignancy or a history of malignancy within the last 5 years (with the exception of successfully treated carcinoma of the cervix in situ and successfully treated basal cell carcinoma and squamous cell carcinoma not less than 1 year prior to Screening \[and no more than 3 excised skin cancers within the last 5 years prior to Screening\]) * Subjects with any infection requiring oral antibiotic or antiviral therapy in the 2 weeks prior to Screening or at baseline, injectable anti-infective therapy in the last 4 weeks prior to baseline, or serious or recurrent infection with history of hospitalization in the 6 months prior to baseline * Subjects with evidence of disseminated herpes zoster infection, zoster encephalitis, meningitis, or other non-self-limited herpes zoster infections in the 6 months prior to baseline * Subjects with planned surgery during the study or surgery ≤ 4 weeks prior to Screening and from which the subject has not fully recovered, as judged by the Investigator * Subjects with diverticulitis or other symptomatic GI conditions that might predispose the subject to perforations, including subjects with history of such predisposing conditions (e.g., diverticulitis, GI perforation, or ulcerative colitis) * Pre-existing central nervous system demyelinating disorders (e.g., multiple sclerosis and optic neuritis) * History of chronic alcohol or drug abuse as judged by the Investigator * Subjects with a known hypersensitivity to any component of the OKZ drug product or placebo * Subjects with a known hypersensitivity or contraindication to any component of the rescue medication * History of severe allergic or anaphylactic reactions to human, humanized, or murine monoclonal antibodies * Female subjects who are pregnant, currently lactating, have lactated within the last 12 weeks, or who are planning to become pregnant during the study or within 6 months of the last dose of study treatment * Female subjects of childbearing potential (unless permanent cessation of menstrual periods, determined retrospectively after a woman has experienced 12 months of natural amenorrhea as defined by the amenorrhea with underlying status \[e.g., correlative age\] or 6 months of natural amenorrhea with documented serum follicle-stimulating hormone levels \>40 mIU/mL and estradiol \<20 pg/mL) who are not willing to use a highly effective method of contraception during the study and for at least 6 months after the last administration of study treatment OR Male subjects with partners of childbearing potential not willing to use a highly effective method of contraception during the study and for at least 3 months after the last administration of study treatment. The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.