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P420 Correlation between Infliximab trough levels and endoscopic activity in ulcerative colitis

S. Bernardo*1, S. Fernandes1, A. R. Gonçalves1, C. Baldaia1, A. Valente1, P. Moura Santos1, L. Correia1, R. Marinho1

1Hospital Santa Maria, CHLN, Gastrenterology, Lisbon, Portugal

Background

Mucosal healing (MH) is currently the main treatment goal in patients with inflammatory bowel disease. Although there is growing evidence supporting the use of therapeutic drug monitoring (TDM) in patients upon loss of response, data correlating TDM and specific treatment target is still lacking. We aimed to assess the correlation between Infliximab (IFX) trough levels and MH in ulcerative colitis (UC).

Methods

Retrospective cohort study including patients with UC under treatment with IFX and at least 1 colonoscopy performed within a 2.6 ± 1.8-month interval of an IFX pharmacokinetic measurement. MH was defined as a Mayo Endoscopic subscore (MES) ≤1. IFX trough levels and antibodies were measured using a drug-sensitive assay (Theradiag®).

Results

Seventy-four pairings of colonoscopy-IFX trough levels were available corresponding to 56 patients (53.6% male with a median age of 36 (range 17–72); 57.1% of the patients were under concomitant immunomodulator therapy. MH was present in 51.4%. Median IFX trough levels were 3.75 (range 0.3–16 μg/ml) and anti-drug antibodies were present in 16.2%. Higher median IFX trough levels were significantly associated with lower endoscopic activity (MES 0–6.2 µg/ml (range 3.6–16); MES 1–7.35 µg/ml (range 3–16); MES 2–2.5 µg/ml (range 2–10) and MES 3–2.2 µg/ml (range 0.3–5.7), p < 0.001). Median IFX trough levels were significantly higher in patients with MH than without MH (6.5 µg/ml (3–16) vs 2.4 µg/ml (0.3–10), p < 0.001). The area under the curve of IFX to predict MH was 0.95 (95% CI 0.894–1.0, p < 0.001). A trough level of IFX ≥3.15 µg/ml presented high sensitivity (97.4%, 95% CI: 80.7–99.0) and high specificity (86.1%, 95% CI: 74.2–97.5) for MH. In multi-variate regression analysis, only IFX trough level above the cut-off value was an independent predictor for MH (p < 0.001).

Conclusion

Higher IFX trough levels are significantly associated with MH in UC. IFX trough levels ≥ 3.15 µg/ml are required to achieve MH.