Abstract As our understanding of the pathogenesis of SpA improves, focus has turned to the role janus kinase (JAK)-mediated signal transduction and inhibiting its actions as a therapeutic mechanism. Small molecule inhibitors of JAK exist, with variable selectivity for the different JAK isoforms. Less selective JAK inhibitors have variable efficacy and safety profiles, prompting the investigation of selective JAK1 inhibition. In this review, we summarize the current phase 2 and 3 clinical trial data, evaluating the use of JAK1 selective inhibitors in the treatment of SpA, particularly AS and PsA. Selective JAK1 inhibition offers a promising therapeutic approach, however further longer-term trials are needed to fully establish their efficacy and safety at higher doses, and their use in the greater continuum of SpA.