Subcutaneous Infliximab Concentration Thresholds for Mucosal and Transmural Healing in Patients With Crohn's Disease

Predose trough concentrations (C_trough) of intravenous infliximab (IV-IFX) during maintenance therapy are associated with therapeutic outcomes in patients with Crohn's disease (CD). A subcutaneous formulation of infliximab (SC-IFX) has shown high C_trough values due to its favourable pharmacokinetics.

To evaluate the association of C_trough of SC-IFX with therapeutic outcomes and the threshold of SC-IFX C_trough for achieving mucosal healing (MH) and transmural healing (TH) in patients with CD.

We performed this cross-sectional study in patients with CD who had received SC-IFX maintenance therapy for ≥ 6 months. We measured SC-IFX C_trough immediately before SC-IFX injection. We performed ileocolonoscopy/single-balloon enteroscopy and/or magnetic resonance enterography within 3 months of SC-IFX C_trough measurement. MH was defined as SES-CD-ulcerated surface subscore of 0. TH was defined as simplified MaRIA score of 0.

We enrolled 124 patients with MH in 77.9% (74/95) and TH in 36.3% (37/102). SC-IFX C_trough was significantly higher in patients with MH (24.1 vs.16.9 μg/mL; p = 0.001) and TH (26.0 vs. 20.5 μg/mL; p = 0.007) than in those without. ROC analysis identified that the threshold of SC-IFX C_trough for MH and TH were 17.5 and 30.3 μg/mL, respectively. Multivariate logistic regression showed that SC-IFX C_trough was significantly associated with MH (OR 1.16; 95% CI 1.05-1.27; p = 0.002) and TH (OR 1.08; 95% CI 1.02-1.14; p = 0.005).

SC-IFX C_trough was positively associated with MH (≥ 18 μg/mL) and TH (≥ 30 μg/mL) in patients with CD, which may guide treatment decisions to optimise therapeutic response in the era of treat-to-target.