Vedolizumab is a humanised monoclonal antibody which specifically binds to integrin α4β7, inhibiting the binding of T lymphocytes to adhesion molecules (MAdCAM-1) mainly expressed in the small intestine and colon, having demonstrated its clinical efficacy in the treatment of patients with inflammatory bowel disease (IBD), both ulcerative colitis (UC) and Crohn's disease (CD).1, 2

The results of two clinical trials, VISIBLE 1 and VISIBLE 23, 4 confirmed the efficacy of subcutaneous (SC) vedolizumab for the treatment of moderate/severe flare-ups in patients with UC or CD at a dose of 108 mg/2 weeks as a maintenance regimen after two induction doses of 300 mg intravenously (IV) four weeks apart. As a result, the European Medicines Agency (EMA) authorised the use of SC vedolizumab in both scenarios.5

The use of SC vedolizumab allows greater autonomy for the patient, as well as fewer adverse effects in relation to IV infusion of the drug, better quality of life and fewer trips to the hospital, with the consequent reduction in indirect costs of the drug.6, 7 However, evidence of the efficacy of switching to SC vedolizumab in patients receiving maintenance therapy with IV vedolizumab comes from real-life patient series8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 with follow-up of less than one year, except for the two Swedish registries8, 9 and the British one published in 2024,20 in which biochemical remission was defined as calprotectin values below 250;µg/g.10, 11, 14, 15, 16, 17, 19 Moreover, in half of them the pharmacokinetics of the drug were not analysed.9, 12, 13, 16,17, 19, 20

Our aims were to evaluate the persistence of SC vedolizumab after the switch, and the clinical and biochemical remission rates at one year of follow-up in all patients with inflammatory bowel disease (IBD) who had been treated with IV vedolizumab for at least six months and were switched to SC vedolizumab, specifically investigating the pharmacokinetics of the drug when given SC and its safety during follow-up.