TNF blockade in the treatment of rheumatoid arthritis: Infliximab versus etanercept

There is accumulating evidence that tumour necrosis factor (TNF) plays a major role in the pathogenesis of rheumatoid arthritis (RA). Recent biotechnological advances have allowed for the development of agents that directly target TNF, a pro-inflammatory cytokine. In the last 2 years, the US FDA and the EU'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 IgG1 and the extracellular domain of the TNF receptor (p75). Infliximab is a chimeric monoclonal antibody (mAb) 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. This review evaluates the available TNF inhibitors, summarises pertinent clinical trials and underscores differences between the two agents in terms of molecular structure, efficacy, safety data, antigenicity and pharmacokinetics.