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.
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.
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.
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.