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* = Presenting author

P481 Serum levels of infliximab associate with early mucosal healing in Crohn's disease: different “therapeutic window” between post-induction and maintenance treatment

Feng T.1, Chen B.1, Mao R.1, Ben-Horin S.2, Chen M.*1

1The First Affiliated Hospital of Sun Yat-sen University, Department of Gastroenterology, Guangzhou, China 2Sheba Medical Center, Department of Gastroenterology, Tel Hashomer, Israel

Background

Serum levels of Infliximab (IFX) was reported be associated with mucosal healing (MH) in Crohn's disease (CD) in some studies. However, association between pharmacokinetics of IFX and early MH remains unknown. We aimed to analyze the association between serum trough IFX level and MH at week 14 (post induction) and week 30 (maintenance) in CD patients, respectively.

Methods

CD patients with scheduled IFX therapy in The First Affiliated Hospital of Sun Yat-sen University between January 2012 and April 2016 were retrospectively screened for complete follow-up data, especially availability of both serum and endoscopy at week 14 or 30,. Serum trough IFX level was measured using enzyme-linked immunosorbent assay. Correlations between IFX level and MH were investigated at week 14 and 30, respectively.

Results

At week 14, 74 CD patients (median age: 19.0 (16.0, 26.0) years, male: 53%) were included and 50 patients achieved MH. Median serum IFX level was significantly higher in patients with MH than those without (4.3 (1.5, 7.1) vs 1.1 (0.3, 2.6) ug/mL, p=0.002). IFX level was negatively correlated with CRP (r=−0.628, p<0.001). Multivariate logistic regression analysis showed that IFX level was an independent risk factor for MH (OR 1.430, 95% CI: 1.125–1.816, p=0.003). IFX level above 4.5 ug/mL identified patients with MH with 50.0% sensitivity and 95.8% specificity (area under the curve = 0.725, p=0.002). Increasing levels of IFX above 8 μg/mL had minimal impact on the achievement of MH. At week 30, 80 CD patients (median age: 19.5 (16.0, 25.0) years, male: 56%) were eligible for analysis and 42 patients obtained MH. Multivariate logistic regression analysis identified IFX level as an independent risk factor for MH (OR 1.337, 95% CI: 1.032–1.731, p=0.028). The optimal cutoff value of IFX level for predicting MH was 2.7 ug/mL (area under the curve=0.793, sensitivity 73.8%, specificity 89.5%, p<0.001). The association between IFX level and increase of MH reached a plateau at 12 ug/mL.

Conclusion

Serum IFX level positively correlated withearly mucosal healing in CD patients. We propose that serum IFX levels of 6–10 ug/mL at week 14 and 10–14 ug/ml at week 30 are required to achieve MH in >80% of patients with CD, respectively, and that this could be considered as “therapeutic window”.