Potential Application of Measuring Serum Infliximab Levels in Rheumatoid Arthritis Management: A Retrospective Study based on KURAMA Cohort Data

Abstract

\n Background Infliximab (IFX) therapy has considerably improved the treatment of rheumatoid arthritis (RA). On the other hand, in some patients, the efficacy of IFX therapy is not adequate, or gradually diminishes with the lapse of the treatment. Although previous studies have reported a positive relationship between serum IFX levels and therapeutic efficacy, the potential application of IFX therapeutic drug monitoring (TDM) in clinical practice remains unclear. The purpose of this study was to investigate the potential applications of IFX TDM by analyzing a Japanese cohort database. Methods Data were collected retrospectively from the Kyoto University Rheumatoid Arthritis Management Alliance, KURAMA,cohort between January 1, 2011, and December 31, 2018. Serum IFX levels were measured using liquid chromatography-tandem mass spectrometry. Results Out of the 311 RA patients who received IFX therapy, 41 were eligible for analysis. Serum IFX levels were significantly higher in responders than in non-responders. An optimal cut-off value was determined to be 0.4 µg/mL based on a receiver operating characteristic curve. At the IFX measurement point, a better therapeutic response was observed in the High-IFX group (n = 31) than in the Low-IFX group (n = 10). Conversely, at the maximum effect point, when DAS28-ESR (the 28 joint disease activity score incorporating erythrocyte sedimentation rate) was the lowest between IFX introduction and measurement points, there were no differences in responder proportions between the Low- and High-IFX groups. Conclusions In clinical practice, IFX primary ineffectiveness could be avoided with appropriate dose escalation without blood concentration measurement. However, IFX TDM could facilitate the identification of secondary non-responders, and in turn, proper IFX use.