Background It is deemed that production of neutralizing antibodies (ABs) is one of the key reasons for loss of infliximab (Inf) efficacy in prolonged ankylosing spondylitis (AS) therapy.
Objectives To evaluate dynamic changes of Inf concentration and anti-Inf ABs level in the serum of AS patients, receiving continuous Inf therapy.
Methods The study included 54 pts (37 males, 17 females) with verified AS diagnosis meeting NY criteria (1984y), high disease activity (BASDAI>4), and regular long term Inf infusions (>1 y, max 10 years). Pts' monitoring included regular blood tests for quantification of anti-Inf ABs (ELISA with commercial kit Immunodiagnostik AG, Germany) and measuring of Inf concentration.
Results Based on Inf efficacy pts were grouped in two arms: Group 1 - 26 (48%) pts with loss of Inf efficacy (exacerbations within 2 – 4 weeks after infusion), Group 2– 28 (52%) with expected response to Inf therapy. In Group 1 anti-Inf ABs were detected significantly more often (p<0.05 Mann-Whitney test), and Inf concentration was lower (p>0.05 Mann-Whitney test) (see Table). Inverse correlation between Inf concentrations and levels of anti-Inf ABs was found in both groups (Spearman correlation).
Conclusions Loss of Inf efficacy may be associated with production of Inf-neutralizing antibodies. Inf serum concentration inversely correlates with levels of anti-Inf antibodies.
Disclosure of Interest None declared