IL-17 inhibitors are another class of biologic medications approved for spondyloarthritis. There are currently two IL-17 inhibitors approved by the FDA for forms of spondyloarthritis — specifically for ankylosing spondylitis (AS) and psoriatic arthritis (PsA). Cosentyx (secukinumab), which was approved for AS and PsA in January of 2016, and Taltz (ixekizumab) approved for PsA in December of 2017, and for AS in August of 2019.
Both IL-17 and TNF-α are inflammatory cytokines (cell signaling molecules) that, as the name implies, signal to activate inflammation throughout the body, modulating or altering the immune system response. Inflammatory cytokines play an important role; however, when there is an overabundance of these, as has been described in inflammatory disease, they can cause harm to the body if left unchecked.
IL-17 and TNF-α cytokines signal to specific immune cells directing them to activate inflammation, with each cytokine being responsible for signaling to a different set of cells. IL-17 and TNF inhibitor medications work by targeting their respective cytokines, obstructing their signaling pathways, and by this mechanism seek to reduce inflammation. Since IL-17 inhibitors target different cytokines than the TNF inhibitors, the hope is that this newer class of biologic medications will help those who haven’t responded well to the TNF inhibitors, or are not able to tolerate them.
IL-17 inhibitors carry similar risks of infections, and reduced ability to fight infections as the TNF inhibitors. They have also shown in clinical trials to exacerbate inflammatory bowel disease in patients who have it, as well as bring on new cases of inflammatory bowel disease.