Comparison of drug survival for Recurrent switching between IL-17 inhibitors and TNF- inhibitors in patients with axial spondyloarthritis

Objective: We aimed to ascertain survival rates of TNF-inhibitors and IL17-inhibitors therapy, as well as the reasons and potential predictors for drug discontinuation and switching in patients with axSpA. Methods: : A longitudinal observational retrospective study was carried out on 148 patients with a clinical diagnosis of axSpA and were on TNF or IL-17 inhibitors recruited from June 2021 to September 2022. Drug survival was recorded as well as the frequency of and reasons for switching biological therapy were reported. Two types of models were used to investigate factors associated with recurrence of switching treatment: Poisson regression (for number of times patients switched treatment) and Cox model for recurrent event (for time to recurrence of switching to another treatment). Results: : The initial biologic taken was IL17-i in 103 patients, and TNF-i in the remaining 45. Disease duration (P=0.01), BMI (P=0.021) and elevated faecal calprotectin (P=0.000), appeared to significantly increase the number of switching with a rate ratio of 1.05, 1.01 and 3.64 respectively. Median drug survival time for the initial, second, and third biologic lines showed no significant difference (P= 0.136) between the three. Elevated faecal calprotectin level was significantly associated with lower survival of IL17-i, (HR: 3.5; P: 0.000). For TNF-i, elevated faecal calprotectin level and higher BMI were significantly associated with lower survival (HR= 4.36 and 1.04 respectively). Conclusions: : IL17-i has proved to have comparable survival to TNF-i in the management of a real-life heterogeneous cohort of axSpA patients irrespective of line of treatment. Increased BMI and faecal calprotectin were predictors of decreased TNF-i survival. Whereas only faecal calprotectin predicted decreased IL17-i survival.