Efficacy, safety and tolerability of tocilizumab in patients with systemic juvenile idiopathic arthritis.

Systemic juvenile idiopathic arthritis (SJIA), a subtype of juvenile idiopathic arthritis, is characterized by systemic features, such as spiking fever, salmon-colored macular rash, serositis, lymphadenopathy, hepatosplenomegaly, and joint inflammation. It is also often complicated with growth retardation, osteoporosis, and sometimes macrophage activation syndrome (MAS) develops, a potentially fatal disease. Pathogenesis of SJIA and MAS is not yet fully understood, but activation of the innate immune system, which causes phagocytosis by dendritic cells, monocytes, and macrophages to produce proinflammatory cytokines such as interleukin-6 (IL-6), IL-1β and IL-18, is thought to be a primary abnormality associated with SJIA. Dysregulated production of IL-6 plays a major role in the development of systemic clinical features. The blockade of IL-6 might thus represent a novel strategy for the treatment of SJIA. Several phase II and III clinical trials of a humanized anti-IL-6 receptor antibody, tocilizumab, proved its outstanding efficacy and tolerable safety profile for SJIA refractory to conventional treatment regimens. This resulted in the approval of tocilizumab for the treatment of SJIA in Japan, India, the EU and the USA.