Infliximab trough levels are decreasing over time in patients with inflammatory bowel disease on maintenance treatment with infliximab

BACKGROUND: Infliximab trough levels (IFX-TLs) and antibodies to infliximab (ATIs) have been suggested as useful markers for the optimization of treatment in inflammatory bowel disease (IBD). We aimed to estimate the patterns over time of IFX-TLs and ATIs in IBD patients on maintenance treatment with IFX. METHODS: Two different measurements of IFX-TLs and ATIs were performed (ELISA; Eagle BioSciences) at a 10-month interval using serum samples of consecutive patients on maintenance treatment with IFX. Certain biomarkers [hemoglobin, erythrocyte sedimentation rate, C-reactive protein (CRP), platelets, albumin] measured at the same time as well as clinical disease activity and quality of life were assessed. RESULTS: Among a total of 86 IBD patients under maintenance treatment with IFX, 64 [49 Crohn's disease, 15 ulcerative colitis (UC), 42 men, mean age 44.2±15.2 years, 41 in combination therapy with immunomodulator, six in intensified dose], with two available measurements of IFX-TLs and ATIs (A and B), were included in the study. The median levels of IF-TLs were 5.07 (interquartiles range: 1.60-12.73) μg/ml in measurement A and 4.68 (1.19-7.83) μg/ml in measurement B (P<0.0001). Patients whose dose was intensified after the first measurement showed an increase in their median IFX-TLs from 1.47 to 8.5 μg/ml, whereas patients with stable IFX dose showed a significant reduction in the median IFX-TLs from 5.65 to 3.8 μg/ml (P<0.0001). In the logistic regression analysis, the decrease in IFX-TL was correlated significantly and independently with the increase in CRP [odds ratio 5.2 (1.4-19.0), P=0.01]. CONCLUSION: IBD patients on maintenance treatment with IFX show decreasing patterns of IFX-TLs over time associated with increasing patterns of CRP levels.