Factors affecting drug survival of an alternative TNF inhibitor and secukinumab in patients with ankylosing spondylitis switching from the first TNF inhibitor

Background: To investigate factors associated with drug survival of an alternative tumour necrosis factor inhibitor (TNFi) and secukinumab (SEC) after switching from the first TNFi in patients with ankylosing spondylitis (AS). Methods: We included a total of 78 patients with AS who switched to an alternative TNFi (n = 56) or SEC (n = 22) from the first TNFi. Patient characteristics at the time of switching and drug discontinuation rate were compared between the two groups. Cox regression analyses were performed to evaluate factors associated with the risk of discontinuing the alternative TNFi and SEC. Results: The proportion of patients with syndesmophytes was numerically lower (28.6% versus 45.5%, p = 0.155) and the C-reactive protein (CRP) level was numerically higher [3.8 (1.0-15.4) mg/L versus 1.1 (0.5-3.5) mg/L, p = 0.060] in patients who received an alternative TNFi. The drug discontinuation rate (alternative TNFi: 35.7% versus SEC: 36.4%, p = 0.957) and reasons for discontinuation were similar (primary failure, p = 0.342; secondary failure, p > 0.999; and adverse events, p = 0.670) between the two groups. A higher CRP level at switching was associated with a lower risk (adjusted HR = 0.93, 95% CI = 0.87-0.99, p = 0.022) of discontinuing the alternative TNFi, and primary failure of the first TNFi was associated with a higher risk [adjusted HR (HR) = 5.20, 95% confidence interval (CI) = 1.91-14.11, p = 0.001]. Current smokers (adjusted HR = 5.77, 95% CI = 1.20-27.74, p = 0.029) and the presence of syndesmophytes (adjusted HR = 7.49, 95% CI = 1.39-40.23, p = 0.019) were associated with a higher risk of discontinuing SEC. Conclusion: When switching the drug from the first TNFi in patients with AS, an alternative TNFi could be preferable in patients with higher CRP levels or syndesmophytes, or current smokers, whereas SEC could be a better choice in patients who presented primary failure of the first TNFi in terms of drug survival.ope