Background/Purpose: Over the last years, and mostly due to lack of alternatives, it has been common practice to start a second TNF inhibitor (TNFi) in patients with axial spondyloarthritis (axSpA) who discontinue their first TNFi. Evidence informing on the effectiveness of this strategy in clinical practice is limited. Importantly it remains unclear whether the reason for discontinuation of the first TNFi influences the response to the second. We aimed to assess whether the reason of discontinuation of the first TNFi influences the response to the second TNFi.

Methods: Patients with axSpA from the ReumaPt national registry, who discontinued their first TNFi and started a second TNFi were included in this analysis. In addition, patients were required to have complete data on Ankylosing Spondylitis Disease Activity Score (ASDAS) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) at baseline, 3 and 6 months after starting the first TNFi. Afterwards, patients were followed every 6 months up to 12 years. The main outcome was the ASDAS clinically important improvement (ASDAS CII). Secondary outcomes were ASDAS major important improvement (ASDAS MI); ASDAS low disease activity (ASDAS LDA); ASDAS inactive disease (ASDAS ID) and BASDAI 50. The reason for discontinuation of the first TNFi was defined as: i) Primary failure, if ASDAS CII was not achieved at 3 or 6 months; ii) Secondary failure if ASDAS CII was achieved at 3 or 6 months but lost in ≥1 visit during follow-up; iii) Adverse events; iv) Other (e.g. pregnancy, surgery). The response to the first TNFi at 3 and 6 months was compared to the response to the second TNFi at the same visits, adjusting for age and gender. The association between the reason of discontinuation of the first TNFi (predictor) and response the second TNFi over time was tested in generalized estimating equations (GEE) models, adjusted for age and gender.

Results: In total, 155 patients (58% male, mean age 41 (SD:11) years) were included, with a median follow-up time on the second TNFi of 1.5 years. Patients had a lower response to the second TNFi compared to the first TNFi according to the main outcome (ASDAS CII) at 3 months (41% vs 51%) and 6 months (35% vs 56%). There was no association between the reason to discontinue the first TNFi and response to the second TNFi as defined by ASDAS CII (Table). This association was present for the most stringent outcomes, namely ASDAS MI and ASDAS ID. Compared to patients who discontinued their first TNFi due to primary failure, patients were more likely to achieve ASDAS ID with the second TNFi when they discontinued their first TNFi due to secondary failure (OR: 5.3 [(95%CI: 1.4; 21.4]), adverse events (OR: 8.7 [2.4; 31.5]), or other reasons (OR: 7.2 [1.5; 34.2]).

Conclusion: In patients with axSpA, response to the second TNFi is worse compared to the first TNFi. The reason to discontinue the first TNFi seems to influence the response to the second TNFi. Patients with a secondary failure to the first TNFi have a better response to the second TNFi compared to those discontinuing the first TNFi due to a primary failure, particularly when response is defined by the most stringent outcomes.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effectiveness-of-switching-between-tnf-inhibitors-in-patients-with-axial-spondyloarthritis-is-the-reason-to-switch-relevant/