What is the best treatment target in axial spondyloarthritis: tumour necrosis factor α, interleukin 17, or both?

After about 15 years of experience with the TNF blockers as the only effective drugs in axial spondyloarthritis patients who fail conventional treatment, for the first time we see now that another targeted therapy, the inhibition of IL-17, is also effective. By indirect comparison of the treatment effect between the two types of drugs, efficacy seems to be on a similar level. This raises quite a few important questions that are related to both pathogenesis and treatment strategies for which the answers are currently largely unknown, but would be of great relevance for optimizing therapies. In this article, we discuss these questions and ways in which such questions could be answered.