Due to a single, unexpected serious event, the trial was stopped.

The purpose of this study is to evaluate the efficacy, tolerability and safety of JNJ-38518168 compared with placebo in adult participants with active rheumatoid arthritis (long time systemic disease of the joints, marked by inflammatory changes in the synovial membranes and bones) despite methotrexate (MTX) therapy.

This is a multi-center (when more than 1 hospital or medical school team work on a medical research study), randomized (the study drug is assigned by chance), double-blind (neither physician nor participant knows the treatment that the participant receives), placebo-controlled (an inactive substance; a pretend treatment [with no drug in it] that is compared in a clinical trial with a drug to test if the drug has a real effect) and parallel-group (each group of participants will be treated at the same time) study. The study will consist of 3 phases; Screening phase (3 weeks), Treatment phase (12 weeks) and Follow-up phase (4 weeks). Each participant will be enrolled in the study for approximately 19 weeks. Participants with active rheumatoid arthritis despite MTX therapy will receive JNJ-38518168, 100 milligram (mg) per day or matching placebo capsules once daily for 12 weeks. Efficacy will be primarily evaluated by change from Baseline in disease activity index score C-reactive protein at Week 12. Participants' safety will be monitored throughout the study.

Inclusion Criteria:

• Participants diagnosed with rheumatoid arthritis (RA) according to the revised 1987 criteria of the ARA (Arnett et al, 1988) for at least 6 months at Screening
• Participants who have been treated with and tolerated methotrexate (MTX) treatment at dosages from 7.5 to 25 milligram (mg) per week inclusive, for a minimum of 4 months before Screening
• Participants if using non-steroidal anti-inflammatory drugs (NSAIDs) or other analgesics (drug used to control pain) regularly for RA, participants must have been on a stable dose for at least 2 weeks before the first dose of study medication
• Participants if using oral corticosteroids (compounds, usually hormonal, taken orally [by mouth] in order to block ovulation [discharge of an egg from the ovary] and prevent the occurrence of pregnancy [carrying an unborn baby]), must be on a stable dose of less than or equal to 10 mg per day of prednisone or another oral corticosteroid for at least 4 weeks before the first dose of study medication and continue with the same dose throughout the study. If not using corticosteroids at study initiation, the participant must have not received any oral corticosteroids for at least 4 weeks before the first dose of study medication
• Participants currently treated with folic acid at a minimum dose of 5 mg per week

Exclusion Criteria:

• Participants having inflammatory disease other than RA
• Participant who have used any of the following medications: D-penicillamine, hydroxychloroquine, chloroquine, oral or parenteral gold salts, sulfasalazine, leflunomide, azathioprine, cyclosporine, tacrolimus, and mycophenolatemofetil
• Participant who have received intra-articular, intramuscular (into the muscle), or intravenous (into the vein) corticosteroids, including adrenocorticotropic hormone (hormone made by the brain that activates the adrenal glands) within 4 weeks before the first dose of the study medication
• Participants who have been treated with any other investigational drug or medical device within 4 weeks or 5 half-lives of the drug, whichever is longer before the first dose of study medication
• Participants who have undergone surgical treatments for RA including synoviectomy (surgical removal of a part of the synovial membrane of a joint) and arthroplasty (surgery to fix a joint) within 3 months before the first dose of study medication