Review of tocilizumab in the treatment of rheumatoid arthritis

Constitutively overproduced in proliferating synovial tissues, interleukin-6 (IL-6) is deeply involved in the pathology of rheumatoid arthritis (RA). Tocilizumab is a humanized anti-human IL-6 receptor antibody that binds to soluble and membrane-bound IL-6 receptor, and at detectable levels in blood, tocilizumab is capable of almost completely blocking the transmembrane signaling of IL-6. In clinical trials for patients with RA in Japan, tocilizumab monotherapy has shown clinical efficacy equaling that of tumor necrosis factor (TNF) inhibitor in combination with methotrexate, and in an extension study in patients who responded to tocilizumab, almost no patients showed a decrease in the efficacy of tocilizumab. Evidence obtained in a phase III study in Japan demonstrated that tocilizumab monotherapy had a sig-nificant inhibitory effect on the progression of structural joint damage compared with that of conventional disease modifying antirheumatic drugs (DMARDs). Furthermore it has been shown that tocilizumab has an excellent ability to suppress serum amyloid A levels and could therefore be an important therapeutic strategy in amyloid A amyloidosis secondary to rheumatic diseases. The safety profile of tocilizumab appears to be satisfactory. However, several serious infections were also reported, and careful monitoring is therefore important during use.