Subcutaneous Infliximab Cutoff Points in Patients With Inflammatory Bowel Disease: Data From the ENEIDA Registry.

Background And Aims: Switching from intravenous infliximab (IV-IFX) to subcutaneous biosimilar infliximab (SC-IFX) has been shown to safely maintain clinical remission and increase drug levels in patients with Crohn's disease (CD) and ulcerative colitis (UC). The aim of this study was to evaluate long-term outcomes after switching from IV-IFX to SC-IFX, including the drug concentration thresholds for maintaining remission and other predictors for loss of response after the switch.

Methods: This multicenter observational study involved CD and UC patients who were in clinical remission for at least 24 weeks and were scheduled to switch from IV-IFX to SC-IFX.

Results: Two hundred and twenty patients were included (74 UC [34%] and 146 CD [66%]). IV-IFX was administered for 52.5 months (range 25-89). Before switch, 106 (49%) patients were receiving intensified IV-IFX. While SC-IFX levels significantly increased following the switch from IV-IFX to SC-IFX, clinical parameters, C-reactive protein, and fecal calprotectin remained unchanged during follow-up. SC-IFX levels were significantly higher in patients receiving the standard IV-IFX dose than in those receiving the intensified dose. Immunomodulatory therapy at baseline and perianal disease had no effect on IFX trough levels, whereas higher body mass index was associated with increased levels. The suggested optimal SC-IFX cutoff concentration for clinical and biochemical remissions based on receiver operating characteristic analysis was 12.2 μg/mL (area under the curve [AUC]: 0.62) at Week 12 and 13.2 μg/mL (AUC: 0.57) at Week 52. Drug persistence was 92% at Week 52, with a good safety profile.

Conclusions: Switching from IV-IFX to SC-IFX safely maintains long-term remission in patients with CD and UC. In maintenance, the optimal cutoff point associated with remission was 12-13 μg/mL.