A multicenter study to evaluate the safety, tolerability, and feasibility of a single intravenous injection of allogeneic MPCs compared to placebo at 12 weeks post-infusion in the treatment of patients with active RA who have received methotrexate +/- other DMARDs for atleast six months prior to screening and who have had an incomplete response to atleast one TNF-alpha inhibitor. This evidence concerns the gene TNF and rheumatoid arthritis.