P0739 Treatment persistence, clinical, and biological outcomes following an elective switch from intravenous to subcutaneous infliximab and vedolizumab

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Abstract Background Subcutaneous (SC) formulations of infliximab (IFX) and vedolizumab (VDZ) are approved for treating ulcerative colitis (UC) and Crohn’s disease (CD). This study reports on treatment persistence, as well as clinical, biological and pharmacological outcomes following an elective switch from maintenance intravenous (IV) to SC IFX and VDZ. Methods We conducted a single–centre, prospective, observational study from November 2021 through June 2024, enrolling stable inflammatory bowel disease (IBD) patients (based on physician global assessment) willing to switch from maintenance IV IFX or VDZ to SC treatment, and with a minimum follow-up of 34 weeks. Data were collected on patient characteristics, prior and current medications, clinical and biological activity, and pharmacokinetics. Assessments were made at time of last IV infusion, baseline (first SC injection, 4 weeks after last IV), week 8, week 34, and last follow-up. The primary objective was SC treatment persistence. Secondary objectives included change in the two-component patient reported outcome (PRO2), C-reactive protein (CRP), faecal calprotectin and serum levels (SL). Results In this study, 140 IBD patients (median age 44.2 years, 78 female, 64 UC, 76 CD) switched from IV IFX (n=59) or VDZ (n=81) to SC treatment. One hundred and fifteen patients were on standard IV dosing versus 25 patients on optimized IV dosing (19 IFX, 6 VDZ). No patient received concomitant immunosuppressants. Over a median follow-up of 20.2 (IQR 13.6-26.4) months, 83.6% of patients remained on the SC formulation, with more patients continuing on SC IFX compared to VDZ (odds ratio 2.56 [95% CI 1.12-5.88], p=0.025, Figure 1). No other baseline factors were linked to treatment persistence. The main reasons for discontinuation were disease flare and side effects (Figure 1). Seventeen patients returned to IV treatment, while six patients switched to another biologic. Median (IQR) PRO2 (for UC: 0 [0-0] at baseline, 0 [0-1] at week 8, and 0 [0-0] at week 34; for CD: 2 [0-7] at baseline, 2 [0-7] at week 8, and 0 [0-6] at week 34), CRP (1.6 [0.7-3.8] mg/L at baseline, 1.4 [0.6-3.7] mg/L at week 8, and 1.9 [0.7-5.1] mg/L at week 34), and faecal calprotectin (30 [30-112] µg/g at baseline, 37 [30-139] µg/g at week 8, and 54 [30-86] µg/g at week 34) remained stable over time. However, median (IQR) IFX and VDZ SL increased significantly over time compared to time of last IV infusion (all p<0.0001) (Table 1). Conclusion Switching from maintenance IV to SC IFX or VDZ is a viable option for stable IBD patients, though 16% experienced flare-ups or side effects after switch. Treatment discontinuation was more common with SC VDZ than IFX.