THU0219 Prospective Analysis of The Immunogenic Response in JIA Patients (Paediatric and Adult) on antiTNF Treatment

Background There is some evidence that clinical response in patients with chronic arthritis treated with antiTNF agents can be influenced by their immunogenicity. This particular has not been fully studied in patients with juvenile idiopathic arthritis (JIA) Objectives To evaluate the immunogenic response against antiTNF agents and its possible impact on treatment efficacy in patients with JIA Methods Seventy-three patients (40 children and 33 adults) fulfilling ILAR criteria of JIA were included. All of them were on treatment with Etanercept (ETN), Adalimumab (ADA) or Infliximab (IFX) +/− Methotrexate (MTX). Demographical and disease characteristics were recorded at baseline. Clinical outcome was prospectively assessed every 6 months (JADAS, patient or parents VAS, physician9s VAS, CHAQ/HAQ, ESR, CRP, number of swollen, painful and limited joints). Patients were tested for the presence of both, serum drug levels and antidrug antibodies levels at baseline and every 6 months Results Thirty-one paediatric patients (77.5%) needed combined treatment (antiTNF + MTX) vs 18 patients (54.4%) in the adult group. Furthermore, paediatric patients followed an intensified antiTNF therapy protocol more frequently than adult patients (54% vs 39.33%; p=0.044). A total of 189 determinations for the assessment of immunogenic response against antiTNF therapy were analysed. No differences were found between children and adults in the prevalence of antidrug antibodies or in the circulating antiTNF levels. No antidrug antibodies were found neither in the 107 determinations of patients following ETN treatment nor in the 6 determinations of patients on IFX. Just 5 (17%) of the 29 patients on ADA treatment produced anti-ADA antibodies at least once during the follow-up period. Regarding the 77 ADA determinations, patients who were on monotherapy with ADA produced antidrug antibodies with a significant higher frequency than patients on combined treatment with MTX (37.5% vs 8.7% of them respectively; p=0.016). Patients on monotherapy with ADA also exhibit a significant reduced serum ADA levels than patients on ADA+MTX (4.73μg/mL vs 12.73μg/mL respectively; p=0.019). However, no significant differences were observed in the ETN concentration between patients on monotherapy or on ETN+MTX treatment (1.50μg/mL vs 1.77μg/mL respectively). No correlation was observed between drug levels or the presence of antidrug antibodies and any of the clinical or biological parameters Conclusions JIA paediatric patients needed intensified and combined with MTX antiTNF therapy more frequently than adults. In spite of this, no differences were found regarding antiTNF levels between children and adults. This fact suggest that children need more therapy to maintain antiTNF concentrations to control the disease activity. No antibodies antiETN were detected in our patients. ADA in monotherapy seems to be more immunogenic than in combined therapy in JIA. We found no correlation between antiTNF levels or the presence of anti-antiTNF antibodies and the clinical outcome of JIA patients Disclosure of Interest None declared