Objectives
To assess the effectiveness and tolerability of first- and second-line interleukin (IL)-17A inhibitor treatment in PsA patients from 2014 to 2021 using data from the Danish Rheumatology Registry (DANBIO) by investigating adherence to therapy.

Method
PsA patients recorded in the DANBIO who received a first- or second-line IL-17A inhibitor treatment were included in this study. All patients included had previously received one or more TNF inhibitor treatment. Baseline characteristics were analysed in subgroups as first-line IL-17A inhibitor treatment and second-line IL-17A inhibitor treatment. Adherence to therapy of first- or second-line IL-17A inhibitor treatments was reported as Kaplan–Meier plots.

Results
A total of 534 patients were included in the study, with 534 first-line switchers (secukinumab: 510, ixekizumab: 24) and 102 second-line switchers (secukinumab: 35, ixekizumab: 67). Baseline characteristics showed a similar HAQ and visual analogue scale (VAS) for pain. VAS global, 28-joint DAS with CRP and the previous number of biologic DMARD treatments were similar, with a greater value for second-line switchers. First-line ixekizumab-treated patients present a younger age, greater percentage of females, a lower disease duration and a lower CRP value. Concomitant MTX use was greater for the first-line secukinumab-treated patients. First- and second-line switchers had a similar adherence to therapy. Second-line secukinumab and second-line ixekizumab switchers showed a similar adherence to treatment.

Conclusion
PsA patients receiving first- or second-line IL-17A inhibitors showed homogeneous baseline characteristics and similar adherence to therapy. Treatment failure of the first IL-17A inhibitor treatment should not preclude a second-line IL-17A inhibitor treatment.