INTRODUCTION
Tumor necrosis factor alpha (TNF alpha) blockers such as infliximab (IFX) and adalimumab (ADA) had significantly changed the course of inflammatory diseases such as rheumatoid arthritis (RA), spondyloarthritis (SpA) and Crohn’s disease (CD). However, about 30% of patients do not respond to these treatments [1]. This lack of response may be due to an immediate non-response known as primary failure, or to a loss of response after an initial good response called secondary failure. In the case of secondary failure, immunogenicity has been incriminated [2]. It is defined by the development of antidrug antibodies (ADAbs) [2].
The presence of ADAbs can decrease serum drug levels by neutralizing the functional part of the biologic or by forming immune complexes between the biologic and the ADAbs, increasing thereby the clearance of the drug [3-5]. Many studies have been performed in order to evaluate the impact of immunogenicity on the clinical response [5]. The aim of this study was to determine the prevalence anti ADAbs against IFX and ADA, and the trough serum concentration of IFX and ADA in RA, SpA or CD patients and to assess their impact on the therapeutic response.