Infliximab is a chimaeric monoclonal antibody to human tumour necrosis factor-alpha (TNFalpha). It binds to both soluble and transmembrane forms of TNFalpha at picomolar concentrations in vitro. Secondary to inhibition of TNFalpha, infliximab reduces serum levels of inflammatory mediators and vascular endothelial growth factor, decreases the expression of chemokines in the synovial tissue and reduces lymphocyte migration into the joints of patients with rheumatoid arthritis. In 2 multicentre randomised double-blind trials conducted over 26 and 30 weeks, infliximab plus methotrexate was significantly more effective than placebo plus methotrexate according to American College of Rheumatology response criteria in patients with active rheumatoid arthritis. A substantial response to infliximab-containing regimens was evident within 2 weeks. Extension phases of these studies indicate sustained clinical efficacy for up to 54 weeks. Of considerable importance are preliminary 1-year radiographic findings that show zero median progression of joint damage in infliximab plus methotrexate recipients compared with a 7 to 8% deterioration in placebo plus methotrexate recipients. Headache, nausea, upper respiratory tract infection and infusion-related reactions are the most commonly reported adverse events with infliximab. Serious events occurred in 4.4% of infliximab versus 1.8% of placebo recipients. In the largest clinical trial, 2 patients died from disseminated infection and 3 developed new or recurrent malignancies, although the exact relationship between infliximab and these events is unknown. To date, 2 patients with rheumatoid arthritis have developed drug-induced lupus. About 10% of patients may develop antibodies to infliximab, although the clinical significance of these is presently unknown.
Infliximab represents an important advance in the treatment of rheumatoid arthritis, with tolerability concerns raised by early studies having been eased somewhat by more recent data in larger patient numbers. If preliminary results indicating that infliximab is able to arrest joint destruction in patients with rheumatoid arthritis are corroborated, the drug will likely become an integral component of future management strategies for this difficult-to-treat condition.