Interleukin-6 (IL-6) is a pleiotropic cytokine with significant functions in the regulation of the immune system. As a potent pro-inflammatory cytokine,
IL-6 plays a pivotal role in host defense against pathogens and acute stress. However, increased or deregulated expression of
IL-6 significantly contributes to the pathogenesis of various human diseases. Numerous preclinical and clinical studies have revealed the pathological roles of the
IL-6 pathway in
inflammation, autoimmunity, and
cancer. Based on the rich body of studies on biological activities of
IL-6 and its pathological roles, therapeutic strategies targeting the
IL-6 pathway are in development for
cancers, inflammatory and
autoimmune diseases. Several anti-IL-6/
IL-6 receptor monoclonal antibodies developed for targeted therapy have demonstrated promising results in both preclinical studies and clinical trials.
Tocilizumab, an anti-IL-6 receptor antibody, is effective in the treatment of various autoimmune and inflammatory conditions notably
rheumatoid arthritis. It is the only
IL-6 pathway targeting agent approved by the regulatory agencies for clinical use.
Siltuximab, an anti-IL-6 antibody, has been shown to have potential benefits treating various human
cancers either as a single agent or in combination with other
chemotherapy drugs. Several other anti-IL-6-based therapies are also under clinical development for various diseases.
IL-6 antagonism has been shown to be a potential therapy for these disorders refractory to conventional drugs. New strategies, such as combination of
IL-6 blockade with inhibition of other signaling pathways, may further improve IL-6-targeted
immunotherapy of human diseases.