Drugs that block tumour necrosis factor: Experience in patients with rheumatoid arthritis

Three biological response modifiers that inhibit tumour necrosis factor-alpha (TNF-alpha) are approved for treating rheumatoid arthritis (RA). Etanercept is a fusion protein comprising two soluble human TNF-alpha receptors linked to the Fc fragment of human immunoglobulin G(1). Infliximab is a chimeric (human/mouse) monoclonal antibody and adalimumab is a humanised monoclonal antibody. In placebo-controlled trials in established disease-modifying antirheumatic drug (DMARD)-refractory RA, the anti-TNF-alpha agents have reduced disease activity, as monotherapy or in combination with methotrexate. In long-term, open-label studies with etanercept or adalimumab, clinical response was sustained for up to 5 years. In early RA, etanercept has similar efficacy to methotrexate. However, etanercept was more effective than methotrexate in preventing radiographic progression. Preventing or delaying disease progression and disability with etanercept therapy in early RA may reduce costs associated with long-term disease outcomes. Data also suggest a benefit of infliximab plus methotrexate or adalimumab plus methotrexate in early RA. All three agents have been shown to improve functionality as assessed by health assessment questionnaire (HAQ) disability scores. Health-related quality of life is also improved in terms of physical and mental health and vitality. Furthermore, etanercept and adalimumab are associated with a reduction in fatigue. Long-term etanercept or infliximab therapy is associated with increased job employment and etanercept also reduces healthcare utilisation. Mild, transient injection-site reactions occur in about 33% of patients treated with etanercept and 20% of patients treated with adalimumab. In patients treated with infliximab, 16-20% have infusion reactions. The incidence of serious infection associated with etanercept and infliximab was low, about 2-3% in etanercept studies of up to 5 years duration, and 5% in a survey of more than 10 infliximab trials. This paper reviews the evidence for efficacy, safety and effectiveness of anti-TNF-alpha agents in RA.