AB0021 IMMUNOGENICITY OF TNF ALPHA ANTAGONISTS IN RHEUMATIC INFLAMMATORY DISEASES : IMPACT ON CLINICAL RESPONSE

Background: One of the mechanisms implicated in the loss of response to TNF alpha antagonists in rheumatic inflammatory diseases is the formation of antibodies against these drugs (anti-drug antibodies: ADAb). Objectives: The objective of our study was to determine the incidence of ADAb anti Infliximab (IFX) and anti Adalimumab (ADA) and to evaluate the therapeutic impact of the presence of ADAb, the rate of ADAb and trough serum concentration of the drug at the time of sampling and six months later. Methods: A longitudinal, prospective and multicenter study was conducted including patients with rheumatoid arthritis (RA) or spondyloarthritis (SpA) treated with IFX or ADA as a first biotherapy for at least six months. ADAb and trough levels were measured. The evaluation of the therapeutic response was made at the time of sampling and six months later. Results: Fifty patients were included (17 RA and 33 SpA). ADAb were positive in 39% of SpA and 35% of RA. They were positive in 40% of cases for IFX and 25% for ADA. The presence of ADAb was negatively related to the trough levels of IFX and ADA during RA (p=0.01 and p Conclusion: The presence of ADAb and low trough levels seem to not affect the therapeutic response in patients on TNF alpha antagonists. Other tracks than immunogenicity should be investigated to explain the loss of response to these biotherapies. Disclosure of Interests: None declared