Factors Associated with the Development of Anti-drug Antibodies to TNFi and the Consequences for Axial Spondyloarthritis: A Two-year Follow-up Study.

Objective: To evaluate the development of anti-drug antibodies (ADAb) against tumor necrosis factor inhibitors (TNFi) therapy during a 2-year period and search the factors linked to patients with axial spondyloarthritis (axSpA). Methods: Biologic-naive patients with axSpA were included in this observational study. Serum drug levels and ADAb were measured at weeks 12, 24, 52, and 104 of treatment by enzyme-linked immunosorbent assay (ELISA). The development of ADAb and factors related to ADAb over time were investigated using generalized estimating equations (GEE). Results: A total of 180 patients with axSpA (116 male, mean (±SD) 45.6 (±11.9) years) who started TNFi treatment (etanercept (32.2%), adalimumab (27.2%), golimumab (20.6%), infliximab (20%)) were included. In the etanercept treatment group, only 1 patient had ADAb at 12 weeks and 24 weeks. Anti-drug antibodies against TNFi drugs were present in the adalimumab group in 32.7% of patients and in the infliximab group in 21.2% of patients at 12 weeks, and the proportion of ADAb-positive patients were found to be stable throughout the follow-up for adalimumab- and infliximab-treated patients. In the golimumab group, one patient had ADAb against golimumab at 12 weeks and the proportion of ADAb-positive patients increased throughout follow-up. In longitudinal analysis, baseline age, TNFi type, longitudinal Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and ASDAS-CRP scores, serum C-eeactive protein (CRP) levels, presence of adverse events and treatment discontinuation were associated with the presence of ADAb. Conclusion: The development of ADAb against TNFi therapy is associated with younger age, high disease activity, the development of adverse events and more common treatment discontinuation in patients with axSpA during 2-year follow-up.