To explore the effect of comedication with conventional synthetic disease-modifying antirheumatic drugs (DMARDs) on drug retention and clinical effectiveness of tumor necrosis factor inhibitors (TNFi) in patients with axial spondyloarthritis (SpA).
The study included all patients starting treatment with a TNFi in a large prospective cohort of axial SpA patients (Swiss Clinical Quality Management in axial SpA). Crude drug retention was analyzed using the Kaplan-Meier method, and in adjusted analyses, Cox proportional hazards regression was used to model TNFi discontinuation. We evaluated multiple disease activity measures and validated clinical response criteria over time.
A total of 2,765 TNFi treatment courses were included from 1,914 patients with axial SpA, 20.4% in combination with a conventional synthetic DMARD. In unadjusted analyses, the monotherapy group had significantly shorter median TNFi retention time (32.7 months) compared to the cotherapy group (39.1 months) (P = 0.04). In multivariate adjusted analyses, the monotherapy group had significantly lower TNFi retention, with a hazard ratio (HR) of 1.17 (95% confidence interval [95% CI] 1.01-1.35). This effect was even larger when only infliximab-treated patients were considered, with an HR for monotherapy of 1.36 (95% CI 1.06-1.74). Clinical response rates were almost identical at 1 year, with a change in the Bath Ankylosing Spondylitis Disease Activity Index of -2.02 and -2.00 (P = 0.83) and a change in the Ankylosing Spondylitis Disease Activity Score using C-reactive protein of -1.14 and -1.12 (P = 0.45) in the monotherapy and cotherapy groups, respectively.
We demonstrate an association between the combination of a TNFi with conventional synthetic DMARDs and improved drug retention in patients with axial SpA, particularly in the subgroup of patients with infliximab.