Subcutaneous versus intravenous infliximab therapy - a real-world study: toward higher drug concentrations.

Background: Recently, a formula of subcutaneous infliximab (SC-IFX) has been approved for inflammatory bowel disease (IBD), demonstrating a better pharmacokinetic and immunogenic profiles, compared to intravenous infliximab (IV-IFX), with similar efficacy and safety.

Aim: The aim of this study is to evaluate the clinical, biochemical, and pharmacological outcomes of IBD patients in clinical remission, who switched from IV-IFX to SC-IFX, with a follow-up period of 6 months.

Methods: Retrospective cohort study, including IBD patients in clinical remission, previously medicated with IV-IFX, who switched to SC-IFX 120 mg every other week. Biochemical parameters were evaluated before the switch and 6 months after, namely infliximab serum concentrations, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and fecal calprotectin.

Results: Included 41 patients in clinical remission, 32 with Crohn's disease (78.0%) and 9 with ulcerative colitis (22.0%). All patients maintained clinical remission during the 6 months after the switch, with a treatment persistence rate of 100%, and no patients requiring corticosteroid therapy, switching back to IV-IFX, or IBD-related hospitalization. The mean infliximab serum concentrations were significantly higher after 6 months of SC-IFX (17.3 ± 6.6 vs. 9.1 ± 5.5 µg/ml, P < 0.001). However, there were no differences between values of ESR, CRP, and fecal calprotectin, before and after the switch (P = 0.791, P = 0.246, and P = 0.639). Additionally, none of the patients developed antibodies to infliximab.

Conclusion: Switching from IV-IFX to SC-IFX in IBD patients in clinical remission is effective and leads to higher infliximab serum concentrations, regardless of the combination with immunomodulatory therapy.