Objective
To investigate real-world effectiveness of tumor necrosis factor inhibitors (TNFi) in patients with axial spondyloarthritis (axSpA) and the association with (i) treatment line (second and third TNFi-series) and (ii) reason for withdrawal from the preceding TNFi [lack of efficacy (LOE) vs adverse events (AE)].

Methods
Prospectively collected routine care data from 12 European registries were pooled. Rates for 12-month drug retention and 6-month remission [Ankylosing Spondylitis Disease Activity Score C-reactive protein inactive disease (ASDAS-ID)] were assessed in second and third TNFi-series and stratified by withdrawal reason.

Results
We included 8254 s and 2939 third TNFi-series; 12-month drug retention rates were similar (71%). Six-month ASDAS-ID rates were higher for the second (23%) than third TNFi (16%). Twelve-month drug retention rates for patients withdrawing from the preceding TNFi due to AE vs LOE were similar for the second (68% and 67%) and third TNFi (both 68%), while for the second TNFi, rates were lower in primary than secondary non-responders (LOE <26 vs ≥26 weeks) (58% vs 71%, P < 0.001). Six-month ASDAS-ID rates for the second TNFi were higher if the withdrawal reason was AE (27%) vs LOE (17%), P < 0.001, while similar for the third TNFi (19% vs 13%, P = 0.20).

Conclusion
A similar proportion of axSpA patients remained on a second and third TNFi after one year, but with low remission rates for the third TNFi. Remission rates on the second TNFi (but not the third) were higher if the withdrawal reason from the preceding TNFi was AE vs LOE.