Objectives To analyze association between the presence of antibodies to infliximab (ATI) and the clinical and biological characteristics in rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients
Methods Sera from RA (n = 22) or SpA (n = 23) patients treated with infliximab were analyzed. ATI and infliximab trough concentrations were measured using a commercial multiplex enzyme-linked immunosorbent assay kit (LISA-Tracker Infliximab Theradiag®, Marne la Vallée, France). Clinical and biological data were collected retrospectively from each patient’s medical file.
Results Infliximab was given in combination with methotrexate (MTX) for 31 (69%) patients (RA patients 90%; SpA patients 43%). Fifteen patients were in remission at the time of analysis. The interval between two consecutive infliximab infusions exceeded 8 weeks for 15 (33%) patients; it was significantly longer for patients who had achieved remission (9.3 weeks) versus the other patients (6.8 weeks; Mann-Whitney U-test, P = 0.0005). Seven (15%) patients were ATI positive (4 RA and 3 SpA), 6 of them were treated in combination with MTX. Duration of infliximab intakedid not differ between ATI positive and negative patients. Their infliximab doses at the time of analysis were comparable, respectively: 4.29mg/kg and 4.13mg/kg (P = 0.74). A longer between-infusions interval was associated with the ATI-positivity (9.6 weeks versus ATI-negativity: 7.3 weeks; P = 0.02). Infliximab trough concentrations were significantly lower in ATI-positive patients (0.18 μg/ml) vs ATI-negative patients (2.1 μg/mL, P = 0.0005). A significant inverse correlation was found between ATI titers and infliximab trough concentrations (Spearman’s test, P = 0.0002, R2 = 0.29). No link was found between the methotrexate intake and ATI-positivity.
Conclusions Immunogenicity of infliximab is related with a longer between-infusion interval, which could affect the treatment strategy, because prolonging those intervals for patients in clinical remission might favor ATI production.
Disclosure of Interest None Declared