A Randomized, Double-blind, Placebo-controlled, Multicenter, Two-part, Dose Ranging and Confirmatory Study With an Operationally Seamless Design, Evaluating Efficacy and Safety of SAR153191 on Top of Methotrexate (MTX) in Patients With Active Rheumatoid Arthritis Who Are Inadequate Responders to MTX Therapy

Primary Objectives: Part A (dose ranging study): To demonstrate that sarilumab (SAR153191/REGN88) on top of MTX was effective on reduction of signs and symptoms of rheumatoid arthritis at 12 weeks. Part B (pivotal study): To demonstrate that sarilumab added to MTX was effective in: * reduction of signs and symptoms of rheumatoid arthritis at 24 weeks * inhibition of progression of structural damage at 52 weeks * improvement in physical function at 16 weeks Secondary Objectives: Part B: To demonstrate that sarilumab added to MTX was effective in induction of a major clinical response at 52 weeks To assess the safety of sarilumab added to MTX To document the pharmacokinetic profile of sarilumab added to MTX in participants with active rheumatoid arthritis who were inadequate responders to MTX therapy.