Background The introduction of tumour necrosis factor inhibitors represents a major advance in the treatment of rheumatoid arthritis (RA). Despite this, up to 40% of patients fail to respond- either due to primary inefficacy or loss of response. One explanation is immunogenicity leading to the development of anti-drug antibodies (ADAb) and low drug levels. Radioimmunoassay (RIA) is a sensitive method to detect ADAb and is less prone to drug interference vs. ELISA. The clinical utility of pharmacological monitoring in routine rheumatology practice is still debated with conflicting opinions. Objectives To evaluate whether ADAb formation and serum drug levels may predict future treatment response of anti-TNF initiated RA patients. Methods 331 patients were selected from the Biologics in RA Genetics and Genomics Study Syndicate prospective cohort [n=160 adalimumab (AD); n=171 etanercept (ETA)]. Serum samples were collected at 3, 6 and 12 months following initiation of therapy. ADAb were measured using RIA and drug levels using ELISA at 3, 6 and 12 months; the timing of blood samples was not consistently pre-dose. Disease activity (DAS28) scores were measured at each visit. Descriptive statistics, multiple linear regression and generalised estimating equation were used as appropriate. Results 835 serial samples were suitable for pharmacological testing (n=414 AD; n=421 ETA). Mean age: 56±13 years; 75% female; baseline DAS28 score 5.9±0.8; median BMI 27.5 (IQR 23.6-32.3). 85% were on a DMARD (56% MTX). ADAbs to AD were detected in 24.8% (31/125 patients at ≥1 time points by 12 months) and in none of the ETA patients. The presence of ADAbs were significantly associated with lower AD drug levels (p <0.0001; rs -0.51; if ADAb titres>100AU p=0.0041; rs-0.66). At 3 months, ADAb formation and low drug levels were a significant predictor of poor ΔDAS28 at 6 and 12 months (p<0.0001, RC -0.0048 95% confidence intervals (CI) -0.0071 to -0.0025). By 12 months, patients who developed ADAbs showed less improvement in disease activity (mean ΔDAS28 2.35; CI 1.67-3.03) than patients without (mean ΔDAS28 3.15; CI 2.86-3.35; p=0.022). Patients who did not develop ADAbs were more likely to be co-treated with MTX (61.4% vs. 43.7% p=0.01). AD drug level was the most significant independent predictor of ΔDAS28 at all time points after adjusting for confounders (p <0.0001, RC 0.12, CI: 0.06-0.18). At 12 months, patients on ETA with higher drug levels (>15μg/mL) were more likely to achieve a good EULAR response than patients with sub-therapeutic levels (<0.0035 μg/mL) (p=0.01). High BMI was the strongest predictor of low drug levels (ETA, p<0.0001, RC -5.97; CI -8.75 to -3.19; AD, p<0.0001, RC-3.86; CI -5.72 to -2.00). Conclusions At 3 months ADAb formation and low AD drug levels are a significant predictor for poor treatment response at 6 and 12 months. In addition low AD drug levels were the strongest independent predictor of poor treatment response at all time points. Acknowledgements Supported by Medical Research Council [grant...

Background Patients with rheumatoid arthritis (RA) have an elevated risk of cardiovascular disease (CVD), predominantly ischaemic heart disease (IHD). Systemic inflammation is thought to be a key contributor to this risk and it is hoped early therapeutic suppression of inflammation will reduce cardiovascular (CV) events in the long term. Insulin resistance, associated with metabolic syndrome, N-terminal pro-brain natriuretic peptide (NT-proBNP) and atherogenic lipid profiles have been proposed as potential surrogate measures of atherosclerosis in RA. Each has been shown to correlate with systemic inflammation, but their utility in RA above measurement of the acute phase response remains unknown. Objectives To determine whether suppression of inflammation in early RA influences surrogate measures of atherosclerosis, including the homeostasis model assessment of insulin resistance (HOMA-IR), NT-proBNP and dyslipidaemia. Methods CRP, fasting glucose and lipids, and in a sub-group, NT-proBNP and fasting insulin, were measured at baseline and week 26 in DMARD naïve RA patients, with 3-12 months symptoms, recruited into the Infliximab as Induction therapy for Early rheumatoid Arthritis (IDEA) multicentre double-blind randomised controlled trial. Patients met the 1987 ACR criteria. Treatment was randomised to IFX +MTX or MTX with 250mg IV methylprednisolone as induction therapy. 120mg IM methylprednisolone was given if DAS>2.4 at 3 time points within the first 26 weeks. HOMA-IR was calculated at each time point. Descriptive statistics, Wilcoxon and paired t-test, and Spearman’s correlation were performed. Results Data from 112 patients (69% female, mean age 53 years, 55% RF and 70% anti-CCP positive) were analysed. At baseline, 9% were on a statin and 14% an anti-hypertensive agent. 4 patients had known IHD and were excluded from the subsequent analysis. The median (range) CRP was 13mg/l (0-30) with CRP normal (<5.0mg/l) in 33%. Baseline CRP negatively correlated with HDL (rho -2.78, p=0.024) and total cholesterol (TC) (rho -2.33, p=0.026). 15%, 30%, 39%, and 25% had at risk levels for HDL, LDL, TC and triglyceride (TG), respectively1. In the subgroup of 79 patients with data on NT-proBNP and fasting insulin, 17% and 38% of patients had raised levels of NT-proBNP and HOMA-IR, respectively. Comparing week 26 to baseline, there was a significant fall in CRP (p<0.001; normal levels in 64%) and HOMA-IR (p=0.008; abnormal in 19%), but not NT-proBNP (p=0.132; elevated in 17%). With respect to the dyslipidaemia, HDL and TC rose (p<0.001 and p<0.001 respectively), but there was no significant change in LDL or TG. 5%, 46%, 61%, and 20% had at risk levels for HDL, LDL, TC and TG, respectively. Conclusions In this study, suppression of inflammation was associated with improvement in insulin resistance and increased HDL, but no significant change in NT-proBNP, TG or LDL following 26 weeks intensive RA treatment. Further analyses of biomarkers at week 78 and drug specific effects are underway. Long term follow up is being perfor...

Background:The long term outcomes for patients with rheumatoid arthritis (RA) depend on early and effective disease control. Methotrexate remains the key first line disease modifying therapy for the majority of patients, with 40% achieving an ACR50 on monotherapy(1). There are at present no effective biomarkers to predict treatment response, preventing effective personalisation of therapy. A putative mechanism of action of methotrexate, the potentiation of anti-inflammatory adenosine signalling, may inform biomarker discovery. By antagonism of the ATIC enzyme in the purine synthesis pathway, methotrexate has been proposed to increase the release of adenosine moieties from cells, which exert an anti-inflammatory effect through interaction with ADORA2 receptors(2). Lower expression of CD39 (a cell surface 5-’ectonucleotidase required for the first step in the conversion of ATP to adenosine) on circulating regulatory T-Lymphocytes (Tregs) was previously identified in patients already established on methotrexate who were not responding (DAS28 >4.0 vs <3.0)(3). We therefore hypothesised that pre-treatment CD39 expression on these cells may have clinical utility as a predictor of early methotrexate efficacy.Objectives:To characterise CD39 expression in peripheral blood mononuclear cells in RA patients naïve to disease modifying therapy commencing methotrexate, and relate this expression to 4 variable DAS28CRP remission (<2.6) at 6 months.Methods:68 treatment naïve early RA patients starting methotrexate were recruited from the Newcastle Early Arthritis Clinic and followed up for 6 months. Serial blood samples were taken before and during methotrexate therapy with peripheral blood mononuclear cells isolated by density centrifugation. Expression of CD39 by major immune subsets (CD4+ and CD8+ T-cells, B-lymphocytes, natural killer cells and monocytes) was determined by flow cytometry. The statistical analysis used was binomial logistic regression with baseline DAS28CRP used as a covariate due to the significant association of baseline disease activity with treatment response.Results:Higher pre-treatment CD39 expression was observed in circulating CD4+ T-cells of patients who subsequently achieved clinical remission at 6 months versus those who did not (median fluorescence 4854.0 vs 3324.2; p = 0.0108; Figure 1-A). This CD39 expression pattern was primarily accounted for by the CD4+CD25 high sub-population (median fluorescence 9804.7 vs 6455.5; p = 0.0065; Figure 1-B). These CD25 high cells were observed to have higher FoxP3 and lower CD127 expression than their CD39 negative counterparts, indicating a Treg phenotype. No significant associations were observed with any other circulating subset. A ROC curve demonstrates the discriminative utility of differential CD39 expression in the CD4+CD25 high population for the prediction of DAS28CRP remission in this cohort, showing greater specificity than sensitivity for remission prediction(AUC: 0.725; 95% CI: 0.53 - 0.92; Figure 1-C). Longitudinally, no significant induction or suppression of the CD39 marker was observed amongst patients who did or did not achieve remission over the 6 months follow-up period.Figure 1.Six month DAS28CRP remission versus pre-treatment median fluorescence of CD39 expression on CD4+ T-cells (A); CD25 High expressing CD4+ T-cells (B); and ROC curve of predictive utility of pre-treatment CD39 expression on CD25 High CD4+ T-cells (C).Conclusion:These findings support the potential role of CD39 in the mechanism of methotrexate response. Expression of CD39 on circulating Tregs in treatment-naïve RA patients may have particular value in identifying early RA patients likely to respond to methotrexate, and hence add value to evolving multi-parameter discriminatory algorithms.References:[1]Hazlewood GS, et al. BMJ. 2016 21;353:i1777[2]Brown PM, et al. Nat Rev Rheumatol. 2016;12(12):731-742[3]Peres RS, et al. Proc Natl Acad Sci U S A. 2015;112(8):2509-2514Disclosure of Interests:None declared