IL-23/IL-17 axis in the pathogenesis and treatment of systemic lupus erythematosus and rheumatoid arthritis

Interleukin-23 (IL-23) and IL-17 are the gatekeepers of CD4+ T helper 17 (Th17) cells where IL-23 is required for the development and expansion of Th17 cells that subsequently produce IL-17 to promote inflammation. Owing to such pro-inflammatory properties, the IL-23/IL-17 axis has emerged as an important mechanism in the pathogenesis of autoimmune diseases including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). In recent years, therapeutic antibodies targeting IL-23 (e.g. ustekinumab, tildrakizumab, guselkumab) or IL-17 (e.g. brodalumab, secukinumab, ixekizumab) have been approved for the treatment of various autoimmune diseases. In this review, we describe the pathogenic mechanisms of IL-23/IL-17 axis in SLE and RA, as well as summarising the findings from phase II and III clinical trials of anti-IL-23/IL-17 therapeutic antibodies in SLE and RA patients. In particular, phase II study has demonstrated that the anti-IL-23 antibody (ustekinumab) confers enhanced treatment outcomes in SLE patients, while anti-IL-17 antibodies (secukinumab and ixekizumab) have shown improved clinical benefits for RA patients in phase II/III studies. Our review highlights the emerging importance of targeting the IL-23/IL-17 axis in SLE and RA patients.