Background Recently, a subcutaneous formulation of biosimilar infliximab (CT-P13) (SC-IFX) has been approved for inflammatory bowel disease (IBD). The aims of this study were to evaluate efficacy, safety, pharmacokinetics and patient experience following a switching to SC-IFX in patients who are in clinical remission on IV-IFX maintenance treatment. Methods Multicentre, descriptive, and observational study including Crohn’s disease (CD) and ulcerative colitis (UC) patients who were going to be changed from IV-IFX to SC-IFX on the ENEIDA registry (a large, prospectively maintained database of the Spanish Working Group in IBD–GETECCU). All patients were on clinical and biological remission at least 24 weeks before changing. Demographic and disease data, clinical activity (Harvey-Bradshaw index for CD and mayo index for UC), analytical data (C reactive protein (CRP) and fecal calprotectin (FC), as well as trough levels were collected at baseline, at 12 and 24 weeks. Results One hundred and fifty-five patients were included: 54 UC (35%) and 91 (65%) CD; 44% women and 56% men; age 45.5 years (32-55). IV-IFX was mainly administered due to active disease (72%) and perianal disease (7%) and during 32 months [range 14-56]. Pre-switch, 78 (50.3%) were on 8-weekly dosing of IV-IFX, 77 (49.7%) were with intensification dose and the half (50.3%) were on concomitant immunomodulatory therapy. SC-IFX was mainly switching by COVID-19 pandemic (60%), to increase through levels (15%) or patient request (25%). The majority of patients (140, 90%) remained with standard dose, 8 (5%) required dose intensification (120 mg weekly in 4 and 240 mg every 2 weeks in 4) and 7 (4.5%) had successful de-escalation (120 mg every 3 weeks in 4 and 120 mg every 4 weeks in 3). Clinical indices, CRP levels and FC remained unchanged (Figure). Median SC-IFX levels significantly increased from baseline of 4.5 μg/dl [range 2.6-9.2] to 14 μg/dl [range 9.5-16.2] at week 12 and 13.2 μg/dl [range 10.4-19.7] at week 24. No factors (immunossupresor, body mass index, disease location) were associated with the increase of IFX trough levels. During 24 weeks of follow-up, 16 of the 78 patients (20.5%) stopped immunosuppressant treatment. The adverse events were recorded in 9 patients (5.8%), 4 (2.6%) were hospitalized and 4 (2.6%) had surgery (one of them for perianal disease). Nine patients (5.8%) stopped SC-IFX (1 primary failure, 2 loss of response, 4 adverse events, 1 voluntarily, and 1 surgery). Conclusion The switch from IV to SC IFX maintains clinical remission safely in IBD patients, offers higher drug levels and a good patient acceptance. However, the significance of higher drug levels with SC-IFX requires further exploration.

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Background A new formulation of biosimilar infliximab (IFX) has recently been approved for subcutaneous administration (SC) that may offer pharmacokinetic advantages resulting in higher drug exposure. Our purpose was to evaluate the efficacy, safety, pharmacokinetic changes and patients’ acceptability after switching from intravenous (IV) to SC IFX in a cohort of patients with Inflammatory Bowel Disease (IBD) in clinical practice. Methods Observational, prospective and single-center study including patients with IBD in sustained (≥6 months) clinical remission under IV IFX that were switched to SC IFX 120 mg every 2 weeks. Prospective monitoring was performed with clinical and laboratory data including IFX trough levels prior to the last IV infusion (W-IV), prior to the first SC administration (W-0), and after 16 weeks (W-16) and 52 weeks (W-52) of SC treatment. Patients’ satisfaction has been evaluated at W-52. A descriptive analysis of the data has been carried out with the R Studio statistical program using means and Wilcoxon signed rank test. Results Sixty patients have been included, all have achieved W-16 and twelve W-52. Thirty-five (58,3%) are men with a median age of 42,5 (20-71) years. Thirty-eight (63,3%) have Crohn’s disease and twenty-two (36,7%) ulcerative colitis, with a median disease duration of 11,3 years. They have been receiving IV IFX (5mg/kg/8 weeks in 95% of cases) for 5,7 (0,6-21,1) years, at a stable dose (≥6 months). Twenty-seven (45%) received concomitant immunomodulatory treatment and IFX was the first biological in 75% of patients. None of the patients presented clinical relapse during follow-up (Table 1). Median trough IFX levels under IV treatment were 3,9 µg/dl (W-IV) and 4,3 µg/dl (W-0). Compared to W-0, IFX trough levels were significantly higher both in W-16 [17,05 µg/dl (5,59–57,60), p<0,005] and in W-52 [16,75 µg/dl (8,65 –35,01), p=0,007], without significant differences between W-16 and W-52 (p=0,74) (Figure 1). None of the patients developed immunogenicity. Three adverse effects have been detected: 1 allergic reaction to the first SC dose and 2 mild skin reactions. At W-16 and W-52 the number of patients maintaining SC IFX treatment were 58/60 (96,7%) and 10/12 (83,4%) respectively. At W-52, all patients expressed high satisfaction with the change and would not like to return to IV treatment. All place the SC route as a preference above the IV. Conclusion Switching from IV to SC IFX is safe, effective, and well accepted by patients with stable IBD. A significant increase in IFX trough levels is observed with the SC formulation.

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