FRI0265 Immunogenicity of Anti-TNF Antagonists in Patients with Rheumatoid Arthritis or Polyarticular Psoriatic Arthritis in Clinical Remission or Low Disease Activity: The Inmunoremar Study: Table 1
Authors: R. Sanmarti, J. Inciarte, P. Estrada Alarcόn, M. Garcia Manrique, A. Gonzalez Navarro, J. Narvaez, J. Rodríguez-Moreno, A. Gomez-Centeno, J. Yagüe
Journal: Annals of the Rheumatic Diseases (2014)

<h3>Objectives</h3> To determine serum trough levels and anti-drug antibodies (<i>Ab</i>) in patients with rheumatoid arthritis (<i>RA</i>) or polyarticular psoriatic arthritis (<i>PsA</i>) in clinical remission (<i>CR</i>) or low disease activity (<i>LDA</i>) on treatment with adalimumab (<i>ADA</i>), etanercept (<i>ETN</i>) and infliximab (<i>IFX</i>) and correlate serum trough levels and Ab with loss of CR o LDA after 1-year of follow-up. <h3>Methods</h3> Prospective, multicenter study of patients diagnosed with RA or PsA attended by 3 hospital outpatient clinics in Catalonia,Spain treated with ADA, ETN or IFX for ≥3 months in CR or with LDA measured by DAS28-ESR at ≥2 consecutive visits. We determined Ab and serum trough levels (commercial ELISA Kit Promonitor®, Progenika SA) at 0,4,8 and 12 months. Variables collected: demographic data; disease activity (different articular indexes), diagnosis; disease duration; biologic drug; reduced dose, and concomitant DMARDs therapy. Study entry data (Visit 0) are presented. <h3>Results</h3> 165 patients (RA 92 [55.8%], PsA 73 [44.2%]),65.5% female, mean age 57±12 years were included. 121 (73.3%) patients were in CR, 44 (26.7%) with LDA, 63 on ADA, 83 ETN, and 19 IFX. Mean treatment duration was 65.2±40.7 months. 75 patients (45%) were receiving low doses of biologics, and 98 (59.4%) concomitant DMARD (84% methotrexate). In 3 patients (1.8%, 2 in CR and receiving DMARD) significant Ab levels were found, with undetectable serum trough levels (2RA and 1PsA): 2 anti-IFX (10%) and 1 anti-ADA (1.6%). Another patient receiving ADA had low Ab titers and detectable serum drug levels. Mean serum levels of all TNF antagonists were non-significantly different between RA and PsA, monotherapy or combined treatment. Patients with reduced dosage had significantly-lower levels of ADA and ETN than those receiving standard doses. No differences between patients in CR or LDA were observed. According to the ELISA cut-off for appropriate drug serum levels (ADA: &gt;1.274μg/ml, and ETN :&gt;1.242μg/ml) (Chen DY et al. Ann Rheum Dis 2014;0:1-9), 19% and 30.1% of patients treated with ADA and ETA, respectively, had suboptimal levels (30% with ADA and 46.2% with ETA on dose reduction). There were no differences between DAS28-CPR, DAS28-ESR, SDAI, CDAI, ESR or CRP values in patients with suboptimal or appropriate serum levels. <h3>Conclusions</h3> The frequency of anti-drug antibodies is very low in patients with RA and PsA treated with TNF antagonists in CR or with LDA. A significant percentage of patients had suboptimal drug serum trough levels. Prospective follow-up will determine whether these serum levels may predict loss of CR or LDA. <h3>Disclosure of Interest</h3> R. Sanmarti Grant/research support: Unrestricted grant from Pfizer, J. Inciarte Grant/research support: Grant from Hospital Clinic of Barcelona (Premi Emili Letang 2013), P. Estrada Alarcόn: None declared, M. Garcia Manrique: None declared, A. Gonzalez Navarro: None declared, J. Narvaez Grant/research support: Unrestricted grant from Pfizer, J. Rodríguez-Moreno Grant/research support: Unrestricted grant from Pfizer, A. Gomez-Centeno Grant/research support: Unrestricted grant from Pfizer, J. Yagüe Grant/research support: Unrestricted grant from Pfizer <h3>DOI</h3> 10.1136/annrheumdis-2014-eular.4682