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Golimumab is a monoclonal anti-tumor necrosis factor alpha antibody, which is used in ulcerative colitis with an exposure-response relationship. The goal of this study was to compare results obtained with different immunoassays (golimumab and antigolimumab antibodies trough levels).This study was based on samples from 78 ulcerative colitis patients on golimumab treatment. Golimumab was quantified by either an anti-IgG detection antibody (Theradiag, Marne la Vallée, France) or an antibody directed against golimumab (Sanquin, Amsterdam, The Netherlands, KU Leuven, Leuven, Belgium, and Janssen RD, San Diego, CA). Bridging drug-sensitive enzyme-linked immunosorbent assays (Theradiag, Janssen RD, and KU Leuven), a bridging drug-tolerant enzyme-linked immunosorbent assay (Janssen RD), and a radioimmunoassay (Sanquin) were used to quantify antidrug antibody.Median serum golimumab levels were 4.5, 3.5, 4.9, and 2.4 mcg/mL with Theradiag, Sanquin, KU Leuven, and Janssen RD assay, respectively (P0.05). Correlation coefficients between assays ranged from 0.9 to 0.97. When using the KU Leuven and Janssen RD assays, 86% of samples were in the same quartile of distribution of values, and for Sanquin and Janssen RD assays, this overlap was 80%. The concordance observed for the other pairs was 83% (Sanquin/KU Leuven RD), 71% (Theradiag/KU Leuven), and 68% (Theradiag/Janssen RD and Theradiag/Sanquin). The specificity of assays for golimumab was demonstrated. Antidrug antibodies were detected in 28.2% of the samples with the Janssen RD drug-tolerant assay and in the same 2 patients by the 3 other assays.Performances of these immunoassays were similar in terms of quality, but differences in the quantitative results point to the importance of using the same assay consistently to monitor a patient's treatment.

Background SB2, an infliximab (IFX) biosimilar to the reference infliximab (R.I.) product (Remicade), received approval in the European Union for all IFX indications. Many decision algorithms based on the measurement of IFX trough levels and antibodies to infliximab are being increasingly used to optimize IFX treatment. The aim of our study was to evaluate whether the biosimilar SB2 could be efficiently monitored using the LISA-TRACKER IFX and anti-IFX assays developed by Theradiag (Croissy Beaubourg, France). Methods Standard curves of R.I. and SB2 were compared, and then accuracy of the LISA-TRACKER IFX assay in detecting the spiked concentration of SB2 was measured. Levels of IFX from SB2 spiked samples and R.I. clinical samples were calculated. Intra-run and inter-run imprecision were also measured with SB2 spiked samples. The ability of polyclonal antibodies directed against R.I. to block the detection of SB2 using the LISA-TRACKER IFX assay and the capacity of SB2 to block the detection of anti-R.I. antibodies using the LISA-TRACKER anti-IFX assay were tested. Results Twelve patients treated with SB2 including 2 patients with SB2-specific antibodies were measured with the LISA-TRACKER anti-IFX assay. We demonstrated that the LISA-TRACKER assay is suitable for the quantification of SB2 in human serum samples. The percentage of recovery was between 82% and 113%. High intra-run and inter-run imprecisions were obtained with the LISA-TRACKER infliximab assay for the quantification of SB2 (SD ranged from 3.3% to 17.9%). The SB2-blocking capacity of R.I. polyclonal antibodies in spiked samples was demonstrated with inhibition between 80% and 97%. SB2 trough levels and anti-SB2 antibodies have also been confirmed in SB2-treated patients. Conclusions LISA-TRACKER IFX and anti-IFX assays are suitable for the monitoring of patients treated with SB2.