In recent years the use of biotechnological agents has drastically revolutionized the therapeutic approach and the progression of rheumatoid arthritis (RA). In particular, interleukin-6 (IL-6) has been demonstrated as a pivotal cytokine in the pathogenesis of the disease by contributing to both the innate and the adaptive immune system perturbation, and to the production of acute-phase proteins involved in the systemic expression of the disorder. The first marketed IL-6 blocker was tocilizumab, a humanized anti-IL-6 receptor (anti-IL-6R) monoclonal antibody. The successful use of tocilizumab in RA has encouraged the development of other biologic agents specifically targeting the IL-6 pathway, either directed against IL-6 cytokine (sirukumab, olokizumab, and clazakizumab) or IL-6 receptor (sarilumab). One Phase II and six Phase III randomized controlled trials demonstrated a broad efficacy of sarilumab across all RA patient subtypes, ranging from methotrexate (MTX) to tumor necrosis factor inhibitor insufficient responders. In particular, sarilumab as monotherapy demonstrated a clear head-to-head superiority over adalimumab in MTX-intolerant subjects. In addition, compared with tocilizumab, sarilumab showed a similar safety profile with significantly higher affinity and longer half-life, responsible for a reduction of the frequency of administration (every other week instead weekly). All these aspects may be important in defining the strategy for positioning sarilumab in the treatment algorithm of RA. Indeed, observational data coming from post-marketing real-life studies may provide crucial additional information for better understanding the role of sarilumab in the management of the disease. This review summarizes both the biological role of IL-6 in RA and the clinical data available on sarilumab as an alternative therapeutic option in RA patients.
Keywords: biologic drugs; interleukin-6; monoclonal antibody; rheumatoid arthritis; sarilumab.