OP0253 The Early Infliximab Levels Monitoring Can Predict the Developement of Anti-Drug Antibodies in a Cohort of Rheumatoid Arthritis Patients Treated with Infliximab

Background There is strong evidence that correlates the antibodies to infliximab appearance (ATI) with a poor clinical response, but for now sparse literature has demonstrated the predictive value of early serum infliximab (Ifx) levels monitoring with the ADA development Objectives To analize if serum Ifx levels at weeks 2, 6 and 14 can predict the ADA appearance at 6 months and 1 year in rheumatoid arthritis (RA) patients.and to define a predictive cutt-off Methods In this restrospective observational study, 83 RA patients (pts) under Ifx therapy were included. All patients fulfilled the 1987 ACR criteria to be included. The clinical activity was measured by DAS28. The drug and ATI levels were measured at baseline and before each infusion by capture and bridging ELISA, respectively. The data about ATI status were available in 44 patients at 6 months and 42 patients at 1 year. In the statistical study was used receiver-operator characteristics (ROC) analysis to obtain a representative cut-off value for Ifx levels between ATIpositive(+) and negative(−) patients at 6 months and 1 year Results Seventy four out of 83 RA patients were female and most of patients had positive rheumatoid factor (62/83, 74.7%) and ACPA (70/83, 84.3%).The mean of the disease duration was 15.46±8.96 years and the time on biological therapy 5.42±3.49 years. At baseline, all patients had active disease measured by DAS28 (5.49±1.35). Fourteen out of 44 (31.8%)patients were ATI+ at 6 months and 12 out of 42 (28.6%) at 1 year. The area under the curve to predict presence of ATI at 6 months was 0.790 (95%CI 0.624-0.957,p=0.002) at week 2, 0.885 (95%CI 0.766-1.000,p=0.001)at week 6 and 0.966 (95%CI 0.913-1.000,p=0.0001) at week 14. For the predictive value of ATI development at 1 year, the area under the curve was 0.773 (95%CI 0.604-0.942,p=0.002)at week 2, 0.853 (95%CI 0.725-0.982,p=0.001) at week 6 and 0.951 (95%CI 0.877-1.000,p=0.001) at week 14. The cut off of Ifx levels to predict ATI appearance at 6 months and 1 year are shown in Table Conclusions The early Ifx levels monitoring has a high value to discriminate what RA patients on Ifx therapy will develop ATI during the treatment. These findings can help to know what patients are more likely to develop a secondary inefficacy associated to immunogenicity Disclosure of Interest P.-R. Chamaida Grant/research support: Pfizer, D. Pascual-Salcedo Grant/research support: Pfizer, Speakers bureau: Pfizer, M. Bonilla: None declared, A. Villalba: None declared, M. Lόpez-Casla: None declared, D. Peiteado: None declared, S. Garcia-Carazo: None declared, S. Ramiro: None declared, K. Franco: None declared, D. Cajigas: None declared, E. Martin-Mola Speakers bureau: Pfizer, Roche, Abbvie, UCB, A. Balsa Grant/research support: Pfizer, Speakers bureau: Pfizer, Roche, Abbvie DOI 10.1136/annrheumdis-2014-eular.3237