Targeting IL-6: A review of data

Abstract

Compounds that target interleukin (IL)−6 pathways include antibodies against the IL-6 receptor or ligand, and inhibitors of IL-6 signal transduction. The anti-IL-6 receptor (IL-6R) monoclonal antibody tocilizumab has been licensed for several years; data from multiple studies demonstrate its efficacy and tolerability in rheumatoid arthritis as monotherapy or in combination with methotrexate. In addition, another anti-IL-6R monoclonal antibody, sarilumab, has recently been approved in both the US and EU. Anti-IL-6 monoclonal antibodies include olokizumab and clazakizumab, which both have data from phase II studies, as well as sirukumab which has completed phase III trials but may not be brought to the market. Comparative data for olokizumab versus tocilizumab intervention in rheumatoid arthritis suggest no difference in efficacy between blocking the receptor or the ligand. Head-to-head studies are needed to determine whether inhibition of the Janus kinase pathway is similar in its overall efficacy to direct inhibition of IL-6 or its receptor. The IL-6 inhibitors appear to be more effective when combined with methotrexate. However, they have shown superiority to tumour necrosis factor inhibitors when used as monotherapy, and may have an advantage in patients who cannot use methotrexate or any other conventional synthetic disease modifying anti-rheumatic drug. Regarding disease activity assessment, CDAI is a more appropriate measure than DAS28 when looking at the effect of IL-6 inhibition, as these agents interfere with the acute phase response, which is heavily weighted in the formula of DAS28.