P960 Comparison of clinical outcomes by induction therapy response status in patients with Inflammatory Bowel Disease (IBD) treated with subcutaneous (SC) versus intravenous (IV) infliximab (IFX): Post hoc analysis of a pivotal, randomised controlled trial

Background Clinical associations between initial response and long-term outcome are well established for IV IFX in IBD.1,2 In 2020, SC IFX was approved in Europe for treating moderate-to-severe Crohn’s disease (CD) or ulcerative colitis (UC), based on a pivotal randomised trial (NCT02883452) comparing SC and IV IFX.3 This post hoc analysis investigated clinical outcomes in patients (pts) treated with SC or IV IFX, by response to IV IFX induction. Methods In the pivotal trial, adults with active CD or UC received IV IFX induction (5 mg/kg; Week [W] 0 and W2), before randomisation to SC (n=66) or IV (n=65) arms. W6 clinical response (≥70-point decrease in Crohn’s Disease Activity Index [CDAI] score [CD]; ≥2-point decrease in partial Mayo score with ≥1-point decrease in rectal bleeding subscore or an absolute rectal bleeding subscore of 0 or 1 [UC]) was a stratification factor. The SC arm received SC IFX (120/240 mg for pts weighing <80/≥80 kg) every 2 weeks from W6–54; the IV arm received IV IFX 5 mg/kg every 8 weeks (W6–22), then switched to SC IFX (W30–54). Rates of clinical remission (CDAI score <150 [CD]; partial Mayo score ≤1 [UC]) and trough IFX concentrations (Ctrough) were assessed at W6, W30 and W54. Analyses were descriptive. Results There were 101 induction responders (IRs) to IV IFX, who were randomised to the SC arm (n=49, 74.2%; SC-IR subset) or the IV arm (n=52, 80.0%; IV-IR subset). Correspondingly, there were 17 (25.8%) and 13 (20.0%) induction non-responders (INRs; SC-INR and IV-INR subsets, respectively). In both study arms, IRs had higher clinical remission rates than INRs at both W30 and W54 (Figure A). Comparing by formulation, the SC-INR subset had nearly twice the W30 clinical remission rate of the IV-INR subset (58.8% vs. 30.8%; p=0.159 [Fisher exact test]). In addition, IV-INR subset clinical remission rates numerically increased after pts switched to SC IFX (W30: 30.8% vs. W54: 46.2%; p=0.476 [McNemar test]). These observations were generally consistent with Ctrough findings (Figure B); median Ctrough in the IV-INR subset increased from 1.5 to 18.3 µg/mL (p=0.005 [Wilcoxon signe-drank test]) after switching to SC IFX. Conclusion Findings suggested associations between initial response to IFX induction therapy and positive long-term outcomes for both SC and IV IFX, and supported potential benefits with SC IFX maintenance therapy for INRs, compared with the option of IV IFX maintenance. Given the post hoc nature of the analysis and the small analysis population (thus statistical inconclusiveness), investigation in larger studies is warranted. 1Murthy SK et al. Inflamm Bowel Dis 2015;21:2090–6. 2Wong ECL et al. J Crohns Colitis 2021;15:1114–9. 3Schreiber S et al. Gastroenterology 2021;160:2340–53.