Background Spondyloarthropathies (SpA) include a heterogeneous group of rheumatic diseases that mainly affect the axial skeleton and entheses. Despite the anti-TNF therapy has been demonstrated effective in SpA patients, about 30% of them develop primary or secondary inefficacy. In rheumatoid arthritis (RA) has been shown that the development of antibodies (Ab) against the first anti-TNF determines the clinical response to a second anti-TNF.

Objectives To assess if the effectiveness of second anti-TNF therapy is associated with the development of Ab against the first anti-TNF in SpA patients switching to a second anti-TNF.

Methods We studied 33 SpA patients treated with a second anti-TNF after having an inadequate response to the first anti-TNF therapy. The diagnoses were: 23 (69.7%) Ankylosing Spondylitis (AS), 6 (18.2%) undifferentiated SpA, 2 (6.1%) psoriatic SpA, 1 (3%) SpA associated with inflammatory bowel disease and 1 (3%) reactive SpA. Clinical activity was measured by ASDAS-CRP at baseline to the 1st and 2nd anti-TNF treatment and after 6 months of the switching. Clinical improvement was assessed by the Delta-ASDAS (clinically important improvement ≥1.1). Drug through levels and anti-drug Ab were measured by ELISA at the end of the fist anti-TNF treatment. Statistical analysis was performed using SPSS 11.0.

Results Our cohort included 33 patients, 18 (54.5%) male, mean age of 50.09±10 years and 21 (63.6%) HLA B27 positive. All of them were initially treated with an anti-TNF: 14 (42.4%) with infliximab (Ifx), 3 (9.1%) with adalimumab (Ada), 16 (48.5%) with etanercept (Eta). Nine out of 33 (27.3%) developed anti-drug Ab [8 anti-Ifx Ab (ATI) and 1 anti-Ada Ab (AAA)]. All patients switched to a 2nd anti-TNF, due to inefficacy: 7 (21.2%) to Ifx, 16 (48.5%) to Ada, 5 (15.2%) to Eta, 5 (15.2%) to golimumab. Clinical activity (ASDAS-CRP) was not different at baseline between first and second anti-TNF therapy (3.45±0.99 vs 3.22±0.96, p=0.24). No differences were observed between patients who developed or not anti-drug Ab at baseline to the first (3.34±0.87 with Ab vs 3.50±1.04 without Ab, p=0.93) and second (2.99±0.95 with Ab vs 3.31±0.96 without Ab, p=0.37) anti-TNF treatment. After 6 months of switching to a second anti-TNF, patients who had developed anti-drug Ab had lower clinical activity (ASDAS-CRP) than patients without anti-drug Ab (1.76±0.98 with Ab vs 2.79±1.10 without Ab, p=0.021). Moreover clinical improvement was higher in patients with anti-drug Ab (1.23±1.22 with Ab vs 0.52±1.08 without Ab, p=0.063). Most patients who had clinically important improvement had anti-drug Ab before switching [60% (6/10) vs 40% (4/10), p=0.010].

Conclusions Same as in RA, in SpA, the failure to a first anti-TNF therapy associated with the development of anti-drug Ab predicts a better clinical response to a second anti-TNF. The study of the immunogenicity in the biological treatment failure helps predict the response to a second biological treatment in SpA.

Disclosure of Interest None Declared