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Background Tocilizumab (TCZ), a humanized anti-IL-6 receptor antibody, represents a new treatment strategy for RA patients.Several studies have demonstrated the association between high serum levels of TNF-inhibitors and a good clinical response in patients with RA. Little evidence exists on this relationship for other biological therapies. Objectives To evaluate the association between TCZ serum through levels and disease activity in a cohort of RA patients after one year of treatment with TCZ. Methods 34 RA patients treated with Tocilizumab were included. Clinical activity was assessed using the Disease Activity Score 28 (DAS28-ESR) and the Clinical and Simplified Activity Index (CDAI and SDAI), serological improvement by C-Reactive Protein- CRP- and Erythrocyte Sedimentation Rate-ESR, clinical improvement by the delta-DAS 28 and response to treatment using EULAR criteria at baseline and after one year of treatment. We stratified all patients into quartiles according to the tocilizumab levels (μg/ml) as follows: IQR1: 18.5. A last observation carried forward analysis (LOCF) was performed at the first year of treatment, so patients that dropped out of the therapy before this period were included. Blood samples were collected just before intravenous (i.v) infusion. Serum drug levels were determined by a capture enzymelinked immunosorbent assay (ELISA). Results The baseline demographic and clinical characteristics are shown in Table 1. When patients were categorised into quartiles, IQR1 comprised 8 (24,2%) patients; IQR2, 7 (21,2%); IQR3, 8 (24,2%) and IQR4, 10 (30,3%). Clinical activity (DAS28, CDAI and SDAI) was statistically significant higher in patients with lower serum through levels at the first year [DAS28 (IQR1: 4,46 ±1,5, IQR2: 2,58 ± 0,87, IQR 3: 3,6± 0,79; IQR4: 2,17 ± 0,74; p=0,001), CDAI (IQR1: 23±13,9, IQR2: 7,72 ± 4,44, QIR 3: 13,38± 4,35, IQR4: 6,33 ± 4,62; p=0,003) and SDAI (IQR1: 19,46 ±15,5, IQR2: 9,51± 7,4, IQR3: 12,59 ± 6,31, IQR4: 4,55 ± 3,73; p=0,005)] and also was the number of swollen joints (IQR1: 7,5 ± 6,6, IQR2: 2,29 ±2,06, IQR3: 5,63 ± 4,3, IQR4: 1,1 ± 1,6, p=0,013) and tender joints (IQR1: 5,5 ± 5,7, IQR2: 1,71 ± 2,06, IQR3: 3,13 ± 2,8, IQR4: 0,8 ± 0,9, p=0,014). In addition, the EULAR reponse was worse in those patients with lower serum drug levels [non-responders: 4 (66,7%) in IQR1 vs 1 (16,7%) in IQR2 vs 1 (16,7%) in IQ3 vs 0 (0%) in IQR4, moderate responders: 3 (37,5%) in IQR1 vs 0 (0%) in IQR2 vs 4 (50%) in IQR3 vs 1 (12,5%) in IQR4 and good responders: 1 (5,3%) in IQR1 vs 6 (31,6%) in IQR2 vs 3 (37,5%) in IQR3 vs 9 (47,4%) in IQR4, p=0,006]. In terms of acute-phase reactants, the mean ESR tended to be higher in patients with lower TCZ levels (IQR1: 22,6±14,8 vs IQR2: 5,6±1,6 vs IQR 3: 9,4 ±3,5 vs IQR4: 6,4 ± 3,5, p=0,005), and also CRP levels (RIQ1: 10,2±17,4 vs RIQ2: 2,3 ± 3,4 vs RIQ3 0,56 ± 0,4 vs RIQ 4: 0,42 ± 0,66, p=NS)]. Conclusions The presence of low serum Tocilizumab levels correlates with a worse clinical disease activity. Consequently, measurement of Tocilizumab levels is a valuable tool that might help in the clinical management of patients with Rheumatoid Arthritis. Disclosure of Interest C. Tornero Marin Grant/research support from: Funded by an unrestricted medical grant from Pfizer., C. Plasencia: None declared, D. Pascual Salcedo: None declared, T. Jurado: None declared, M. B. Paredes: None declared, I. Monjo: None declared, E. Moral: None declared, A. Pieren: None declared, G. Bonilla Hernan: None declared, D. Peiteado: None declared, P. Bogas: None declared, L. Nuno: None declared, A. Villalba Yllan: None declared, E. Martin Mola: None declared, A. Balsa Criado: None declared

Background Loss of response of TNFα inhibitors (TNFi) over time resulting in discontinuing of this therapy is a major issue in RA, but underlying reasons for this remains unknown. A few studies suggest the influence of BMI on serum levels of subcutaneous TNFi. However, there is no available data on the possible influence of BMI on infliximab (IFX) serum levels, which is intravenously administred and adjusteing the dose according to patient weight. Objectives To determine the possible influence of BMI on serum IFX levels in patients with RA. Methods Retrospective observational study incluiding 72 patients with RA treated with infliximab, at 3 mg/kg dose in a standard regimen, in our department between 2000 and 2015. Serum IFX levels were determined by ELISA in 3 visits: i)2 weeks, ii)six months and iii)one year after treatment onset. BMI (kg/m 2 ) was classified in four categories: underweight ( Results Characteristics of patients included in the study when initiating IFX therapy were: 88% female, median (range) age 52 (21–82) years, 71% RF+, 79% ACPA+, disease duration 10,4 (1,0–39,0) years, 79% with concomitant methotrexate and 57% with other DMARDs. Median (range) BMI was 25,5 (16,7–40,2) kg/m 2 . According to BMI, patients with underweight, normal, overweight and obesity were 2 (2,7%), 35 (48,6%), 23 (31,9%) and 12 (16,7%), respectively. Median (range) IFX serum levels, in ng/ml, for each of the four BMI categories,and for each of the visits, are presented in Table 1. In the longitudinal analysis, an inverse statistically significant relationship between BMI and drug serum levels was observed: β: -441,7; 95%CI (-829,7 to -53,8). This relationship remained despite of adjusting the model for potential confounders: β: -457,3; 95%CI (-858,8 to -55,8). Conclusions BMI influences serum IFX levels in patients with RA treated with infliximab. Higher BMI values are associated with lower serum drug levels. Acknowledgement Unrestricted grants from Pfizer Disclosure of Interest None declared

Background There is wide scientific evidence about the involvement of smoking in the susceptibility to rheumatoid arthritis. However, the effect of smoking on the activity of the disease and its clinical course is controversial. Objectives To analyze the impact of smoking on disease activity in a cohort of patients with recent onset rheumatoid arthritis. Methods We included a cohort of patients from an Early Arthritis Clinic (EAC), followed up between January 1993 and December 2012. All patients gave informed consent to the study. Patients were included with early arthritis (less than one year of disease duration to the onset), who met the criteria of the American College of Rheumatology (ACR) 1987 for RA at some time during the disease course, and were followed up for two years. Microcrystalline and infectious arthritis were excluded, as well as patients who previously had been treated with disease modifying antirheumatic drugs. Patients were monitored for clinical and analytical data using standardized protocols every six months. The influence of active smoking in disease activity, functional disability and serological variables were studied. Every six months we assessed: number of tender (out of 68) joints (NTJ), number of swollen (out of 68) joints (NSJ), DAS, change in DAS (ΔDAS), HAQ, erythrocyte sedimentation rate (ESR), rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA). Results 398 patients were included in the study, with a mean age at onset of 51.8 years (± 16.1 SD) and a predominance of women (77.6%). Patients were referred to the EAC with a mean of 17.7 weeks (± 13.1 SD) from the onset of symptoms. Active smokers were 27.6% of the patients. At baseline most patients had a subacute (88.7%), symmetrical (88.9%), RF-positive (81.3%), ACCP-positive (67, 5%) polyarthritis (83.1%). Smokers were younger at disease onset (49 ± 13.4 years smokers vs. 52.9 ± 13.4 in nonsmokers, p = 0.022), with a predominance of males (43% males vs. 23% women, p Conclusions Active smoking has a negative impact on the activity of patients with recent onset rheumatoid arthritis, with less improvement as compared to non-smokers. Disclosure of Interest None Declared