Tumor necrosis factor inhibitors: new options for treating rheumatoid arthritis.

There is accumulating evidence that tumor necrosis factor plays a major role in the pathogenesis of rheumatoid arthritis. Recent biotechnological advances have allowed for the development of agents that directly target TNF, a proinflammatory cytokine. In the last 2 years, the U.S. Food and Drug Administration and the European Union's Commission of the European Communities have approved two biological agents for the treatment of refractory RA, etanercept and infliximab. Etanercept is a fusion protein, composed of the Fc portion of immunoglobulin G1 and the extracellular domain of a TNF receptor (p75). Infliximab is a chimeric monoclonal antibody composed of murine variable and human constant regions. In placebo-controlled trials, both agents have proven to be effective and well tolerated in RA patients.