The value of blocking IL-6 outside of rheumatoid arthritis: current perspective

Purpose of review Interleukin-6 (IL-6) is a multifunctional cytokine that regulates immune response and induces acute phase response. Despite the important physiological activities of IL-6, dysregulated overproduction of IL-6 is pathologically involved in various immune-mediated inflammatory diseases (IMIDs) including rheumatoid arthritis (RA). A series of clinical studies of tocilizumab, a humanized anti-IL-6 receptor (IL-6R) antibody, for patients with RA refractory to conventional therapy or anti-tumor necrosis factor therapy have demonstrated the clinical benefit of IL-6 blockade in RA. On the other hand, there is now accumulating evidence that tocilizumab is therapeutically effective for patients with a number of IMIDs other than RA. This review focuses on the perspective of IL-6 blockade therapy for such IL-6-related IMIDs outside of RA. Recent findings A considerable number of case reports and preclinical studies have shown the benefit of IL-6 blockade therapy in various IMIDs such as systemic lupus erythematosus, adult-onset Still disease, Takayasu arthritis, polyarteritis nodosa, systemic sclerosis, reactive arthritis, dermatomyositis, and polymyositis. Summary Blocking IL-6 with tocilizumab can be a therapeutic option for patients with various IMIDs in which overproduction of IL-6 plays a pathological role. Future clinical studies investigating the safety and efficacy will elucidate the clinical benefits of IL-6 blockade therapy for such diseases.