P524 Predictors of immunogenicity in patients with Inflammatory Bowel Disease treated with infliximab: A post hoc analysis of the randomised phase I CT-P13 SC study

Abstract Background CT-P13 SC is the only subcutaneous (SC) formulation of infliximab (IFX) approved to treat Crohn’s disease (CD) or ulcerative colitis (UC). The primary study reported no increased risk immunogenicity (anti-drug antibody [ADA]/neutralising [NAb] positivity) with vs. intravenous (IV) in CD UC patients (pts) despite a numerical trend for lower ADA/NAb positivity dosing.1 It unclear whether high trough levels (Ctrough) during IFX dosing may account these observations. Methods This post hoc analysis part 2 randomised, parallel-group (NCT02883452) evaluated predictors pts treated CT-P13. relationship Week (W) 22 and 30 ADA NAb rates W22 Ctrough, under stable dosing, was examined. optimal threshold Ctrough predicting estimated by receiver operating characteristic (ROC) methodology using data. A generalised linear regression model identified predictive factors at W30. proportion equal above calculated threshold, rates, were determined treatment arm. Results included 131 randomised W6 receive (n=66) IV (n=65) as maintenance treatment. Of 113 both data available W22, 60 negative, 53 positive. At median significantly higher ADA-negative ADA-positive group (16.95 3.44 μg/mL, p<0.0001); differed according quartile (p=0.0009; Fig. 1). ROC showed that 4.695 μg/mL optimally predicted 66.2% sensitivity 77.3% specificity (area curve, 0.766 [95% confidence interval, 0.664–0.869]; 2). Concomitant medication use ≥4.695 associated significant W30 (Fig. 3). had arm (96.5% 25.0%, p<0.001). In arm, (ADA, 36.8% 57.1%, p=0.039; NAb, 7.0% 21.4%, p=0.033; 4). Conclusion level pts, positivity, providing initial evidence on zone tolerance IFX. Reference: 1. Schreiber S et al. Gastroenterology 2021;160:2340–2353.