The purpose of this study is to evaluate the safety and effectiveness of subcutaneous injections (under the skin) of anti-interleukin-6 antibody in combination with methotrexate, compared to methotrexate alone, in rheumatoid arthritis (RA) patients with active RA despite methotrexate therapy. The study drug is a protein that blocks interleukin-6, a substance in the body that is overproduced in RA patients and then factors into the arthritis symptoms and complications of RA.

Increased levels of interleukin-6 (IL-6) contribute to the arthritis symptoms and to the full body complications of rheumatoid arthritis (RA) patients. CNTO 136 is a protein (antibody) that blocks IL-6. This is a multicenter, randomized (patients are assigned different treatments based on chance), double-blind (neither the patient nor the physician knows whether drug or placebo is being taken, or at what dosage), placebo-controlled, parallel group study comparing safety and efficacy of subcutaneous (SC) injections every 2 or 4 weeks of CNTO 136 versus placebo in patients with active RA who have an inadequate response to methotrexate. The study hypothesis is that CNTO 136 SC injections will be more effective than placebo in terms of reducing the signs and symptoms of RA at Week 12, while maintaining an acceptable safety profile. The total duration of treatment with active drug is approximately 10 weeks. All patients are to remain on a stable, weekly dose of methotrexate during the study. Patients who complete the screening period will be randomized to CNTO 136 injections or placebo injections at the start of the study (Week 0). At Week 12, patients will switch treatment to CNTO 136 if they were on placebo, or switch to placebo if they were first on CNTO 136, and they are to continue on these treatments through Week 22. For the patients who started on CNTO 136 and switched to placebo, this 12 weeks of followup is designed to evaluate how long the effect of CNTO 136 can last after the last injection of active CNTO 136. There is a 16 week followup period after Week 22 for study visits and assessments but no further injections. This is a 2-part study in that, first, the dose of CNTO 136 100 mg SC administered every 2 weeks will be compared to placebo injections in 40 patients with active RA despite methotrexate (Part A). If, in Part A, CNTO 136 100mg SC every 2 weeks is found to be an effective treatment, then in the second part (Part B), treatment with CNTO 136 100 mg SC every 4 weeks, 50 mg SC every 4 weeks, and 25 mg SC every 4 weeks will also be evaluated for their effectiveness compared to placebo injections in patients with active RA despite methotrexate. Assessments during the study will include questionnaires, physical exams, evaluation of joint swelling and tenderness, blood samples for safety, for measuring levels of CNTO 136 in the blood and the body's response to CNTO 136, urine samples, and a few electrocardiograms (ECG). In Part A, CNTO 136 100mg, or placebo injections SC every 2 weeks from Week 0 to Week 10, then switching at Week 12 to placebo or CNTO 136 SC every 2 weeks, respectively, through Week 22. In Part B of the study, from Weeks 0 to 10, CNTO 136 100 mg every 2 weeks, 100 mg, 50 mg, or 25 mg every 4 weeks, or placebo injections SC every 2 weeks, then switching at Week 12 to placebo or CNTO 136 100 mg SC every 2 weeks, respectively, through Week 22. Duration of participation: approximately 42 weeks

Inclusion Criteria:

• Have a diagnosis of rheumatoid arthritis (RA) (according to the revised 1987 criteria of the ACR) for at least 4 months prior to screening
• Must have been treated with and tolerated methotrexate (MTX) at a dose of at least 15mg/week for at least 4 months prior to screening, and have a MTX dose of >=15mg/week and stable for at least 6 weeks prior to screening. Doses of MTX doses of 10 or 12.5 mg/week are allowed if patient had intolerance of 15 mg/week
• Have active RA as defined by persistent disease activity with at least 6 swollen and 6 tender joints, at the time of screening and baseline, and either anti-cyclic citrullinated peptide (anti-CCP) antibody-positive or rheumatoid factor (RF) positive at screening
• C-reactive protein >= 1.0 mg/dL (10 mg/L)
• If using oral corticosteroids, must be on a stable dose equivalent to <= 10 mg of prednisone/day for at least 2 weeks prior to first administration of study agent
• Women of childbearing potential and men capable of fathering a child must be willing to use adequate birth control measures during the study and for 6 months after the final dose of study drug.

Exclusion Criteria:

• Cannot have inflammatory diseases other than RA that might confound the evaluation of the benefit of CNTO 136 therapy
• No treatment during the 4 weeks prior to the first administration of study agent with any disease-modifying anti-rheumatic drugs (DMARDs)/systemic immunosuppressives other than MTX, sulfasalazine, hydroxychloroquine or chloroquine
• No prior treatment with biologic anti-TNF drugs (infliximab, etanercept, adalimumab) or with tocilizumab
• No history of, or ongoing, chronic or recurrent infectious disease
• No known infection with HIV, hepatitis B or hepatitis C
• No serious infection within 2 months prior to first administration of study agent
• No known malignancy or history of malignancy within the past 5 years (except for nonmelanoma skin cancer that has been treated with no evidence of recurrence in the past 3 months).