LAUSR

Background The drugs called Anti-TNF inhibitors are capable of inducing an immune response (immunogenicity) Its effectiveness may be affected by the development of Anti-Drug Antibodies (Ab) Objectives To assess the frequency of appearance of Anti-Drug Antibodies: Infliximab (IFX), Adalimumab (ADA), etanercept (ETN) To classify the failures of response To analyse the relationship between anti-TNFα antibodies and concomitant treatment with DMARDs To observe whether there is a link between risk factors and drug levels Methods This is a retrospective, descriptive, observational study of patients with Rheumatoid Arthritis (RA), Spondyloarthritis (SpA), Psoriatic arthritis (PsA), Seronegative arthritis (SA) and Enteropathic arthritis (EA) with active disease and that were treated in the “University Health Care Hospital of Leόn” between Jan-2015 and Jan-2016. Using ELISA Technology and the kits Promonitor®, it was possible to detect serum levels of IFX ADA, ETN (reference values>2.5μg/mL, 5–8μg/mL and 0.8–1.2μg/mL respectively) and of anti-drug antibodies. The samples were collected the same day of the administration, prior to it, always in a trough level. The gathered data was: demographic data, activity, time-to-disease progression, prior treatment with biologics, concomitant DMARDs, duration of the biologic treatment and dosage, quantization levels, anti-TNF antibodies, cardiovascular risk factors (CVRF) and smoking habits. Results Variables to study: N=40: IFX 50%, ADA 30%, ETN 20%. Age 53.6±3.7 years old [95% CI], Women: 55%, time-disease progression: 12.3±2.7 years old. Type of disease: RA 47.5%, SpA 15%, PsA 20%, SA 7.5%, EA 10%. DAS28: 3.5±0.4, BASDAI 4.7±0.5, BASFI 4.3±1.4. Prior treatment with biologics (30%): IFX 15%, ADA 66%, ETN 12.5%. Frequency of administration: IFX 8.6±0.36 weeks, ADA 2.25±0.36 weeks, ETN 1.1±1.0 weeks. Reasons for requesting the levels: Secondary failure (82%): IFX 90%, ADA 66.7%, ETN 75% Primary failure (17%): IFX 5%, ADA 33%, ETN 25% Infusion reactions (2.5%) Drug levels within the therapeutic range: IFX 10%, ADA 41%, ETN 50%. Formation of anti-TNF Ab of the sample: IFX 30%, ADA 16%, ETN 0%. DMARDs: presence of 62.5% (MTXsc 64%, MTXvo 20%, Leflunomide, Sulfasalazine e Hydroxychloroquine 16%). Conclusions We found the following conclusions: In the data collected, we observe that the IFX (30%) is the most immunogenic drug, followed by the ADA (16%) and being the ETN (0%) the one that so far has not presented anti-drug Ab, outcomes in agreement with the medical literature The main reason for requesting has been the secondary failure (90%) The suboptimal levels of the drug and the presence of specific ab are correlated with the loss of clinical response. In our case, the proper range of drug is only objective in 10% of the patients treated with IFX, 41% with ADA and 50% with ETN The concomitant use of DMARDs in our study has not been shown to decrease levels of Ab, being the MTX the most used in our patients (84%). We observed no correlation between the occurrence of Ab, the use of DMARDs or the type of disease The monitoring of the levels of anti-TNF drug may be useful to individualize the treatment, to avoid possible side effects and to make decisions regarding the continuation or change of therapy. Disclosure of Interest None declared