Background:Considerable evidence suggesting enhanced efficacy of anti-TNF therapy for rheumatoid arthritis (RA) when co-administered with methotrexate (MTX) led us to explore the applicability of the published data to our patient cohort.Objectives:This retrospective study aimed to investigate the efficacy of MTX in combination with adalimumab (ADA) and etanercept (ETN) for RA, examining changes in disease activity score (DAS28-CRP) on first starting treatment, and rates of withdrawal due to inefficacy over up to 10 years of treatment in routine clinical practice.Methods:309 patients with RA who had started ADA or ETN as a first-line biologic at UCLH from 2003 onwards were identified. Demographic and treatment details, DAS28-CRP (DAS) at the biologic-naïve baseline and at a first appointment for review on anti-TNF were extracted from clinical records. ANOVA was used to investigate the level of association between change in DAS and anti-TNF type, concomitant therapy, anti-CCP (CCP), rheumatoid factor (RF), age, disease duration and number of DMARD trials by anti-TNF initiation, year of initiation and gender. Kaplan-Meier with log rank tests were used to explore associations between anti-TNF type, MTX, CCP and RF and rates of withdrawal due to inefficacy, and Cox Proportional Hazards to check whether these remained significant after controlling for any other significant factors.Results:179 patients were on ADA and 130 ETN; 44% were on concomitant MTX (Table 1).Table 1.Numbers of patients co-prescribed MTX with ADA or ETN according to CCP statusCCP positive nTotal nETN without MTX3754with MTX5776ADA without MTX5482with MTX6597Median follow up since anti-TNF initiation was 7 years. Median age at initiation was 51 years, and disease duration 4 years. 82% were female. 241 were seropositive, including 24 positive for CCP only and 28 RF only.Mean biologic-naïve (baseline) DAS was 5.75, and 3.52 on first review (mean 20 weeks of treatment, n= 274) with mean change -2.23. MTX, even accounting for dose, failed to explain a significant amount of the variance in DAS response at first review either as a main effect or in interaction with anti-TNF type, CCP or RF. The only significant factor was 4+ DMARD trials prior to initiation (lower mean DAS response, p=0.010).Next, we analysed withdrawal of anti-TNF for inefficacy over up to 10 years. Kaplan-Meier analyses revealed that CCP positive patients had higher inefficacy withdrawal rates (p =0.004). Of note, CCP positive patients treated with MTX had lower withdrawal rates for inefficacy (Figure 1, p=0.006). Intriguingly, there was a trend towards higher rates in patients treated with MTX if CCP negative (p=0.14). Co-administration of MTX appeared to reduce rates of inefficacy withdrawal for patients on ETN (p=0.006) but not ADA (p =0.784). For CCP positive patients on ETN, MTX was strongly associated with lower rates of inefficacy withdrawal (Figure 1, p=.002).CCP status and the CCP*MTX interaction remained significant in the multivariate Cox model (Table 2). The MTX*ETN interaction was also included by the backward stepwise variable selection procedure although with p 0.069.Table 2.Variables in the Cox ModelHazard Ratio for discontinuation related to inefficacy95% CI for HRMTX2.180.93, 5.13CCP3.711.74, 7.92CCP*MTX0.350.14, 0.91ETN*MTX0.610.36, 1.04Disease duration > 5 years0.610.41, 0.90Gender (male)0.620.36, 1.054+ DMARD trials1.651.02, 2.67Biologic-naive Global VAS/cm1.261.11, 1.42Overall model p < .0005RF with a univariate Cox significance of 0.172 was less closely associated with rate of withdrawal for inefficacy compared to anti-CCP positivity (p 0.005).Conclusion:There was no apparent benefit of MTX with anti-TNF with respect to initial DAS response, but MTX was associated with a reduction in withdrawals for inefficacy though only in CCP positive patients treated with ETN.Disclosure of Interests:None declared