First trough level of infliximab at week 2 predicts future outcomes of induction therapy in ulcerative colitis—results from a multicenter prospective randomized controlled trial and its post hoc analysis

Background: Infliximab (IFX) is one of the treatments of choice for corticosteroid-refractory and corticosteroid-dependent ulcerative colitis (UC). A high serum trough level of IFX (TL) is reported to be associated with sustained efficacy during maintenance treatment. As part of a phase 3 randomized controlled trial of IFX in UC, we assessed the predictive value of the first TL at week 2 for short- and long-term response. Methods: Patients received intravenous IFX 5 mg/kg or placebo at weeks 0, 2, and 6. Patients with evidence of a response by week 8 continued treatment at weeks 14 and 22. TL was measured by enzyme-linked immunosorbent assay. Post hoc analysis was then performed for TL and clinical outcomes. Results: Clinical response rate at week 8, the primary end point, was significantly higher in the IFX group than placebo (p = 0.005). The incidence of adverse events between groups was similar. Week 2 TL was significantly associated with a 14-week clinical activity index (CAI) remission. In multiple logistic regression analysis, the week 2 TL-to-CAI ratio (TL/CAI, odds ratio 8.07; 95 % confidence interval 2.84–27.07, p