The prevalence and clinical effect of immunogenicity of TNF-α blockers in patients with axial spondyloarthritis.

Objective: To evaluate the prevalence of immunogenicity of TNF-α blockers in axial spondyloarthritis (SpA) patients and to assess the effect of immunogenicity on drug levels and clinical response.

Methods: Patients with axial SpA treated with either infliximab (INF), adalimumab (ADA) or etanercept (ETN) were recruited to our observational cross-sectional study. Demographic and clinical data were collected and disease activity scores were assessed. Drug trough levels and anti-drug antibodies were measured in serum samples and collected before the next administration.

Results: Thirty-nine patients with axial SpA with a mean age of 46.3±12.7 (10 women) were recruited to the study (14 receiving INF, 16 ADA and 9 ETN). Patients' mean therapy duration was 50.6 months (±46.4) and 6 (15%) of them were using MTX concomitantly with the TNF-α blockers. Anti-drug antibodies were found in 6 (15%) patients (4 with INF and 2 with ADA), all of which had undetectable drug level. No anti-drug antibodies were detected in patients treated with ETN. Immunogenicity was associated with higher BASDAI (Bath Ankylosing Spondylitis Disease Index), ASDAS-CRP (Ankylosing Spondylitis Disease Activity Score) and ASDAS-ESR.

Conclusions: Axial SpA patients failure to respond to TNF-α blockers may be at least partially related to immunogenicity. Measurement of anti-drug antibodies and drug levels in these patients may assist in determining further treatment strategies.