Drug Persistence of Patients with Inflammatory Bowel Disease Under Biological Treatment in the Pre IL-23 Era in a Tertiary Referral Center in Germany

<b>Background/Objectives:</b> Predicting treatment persistence in inflammatory bowel disease (IBD) remains challenging despite a broadened therapeutic arsenal. This study used longitudinal data to assess drug persistence across four biologics for IBD prior to Interleukin (IL)-23 blocker approval. <b>Methods:</b> We retrospectively analyzed IBD outpatients at Goethe University Hospital. Laboratory data and treatment adherence were collected to determine how many patients continued each biological therapy after induction and at 1 year. <b>Results:</b> Of 587 patients, those on azathioprine or mercaptopurine were excluded (focusing on biologics). Four biologicals were analyzed: 280 patients received one of them; 312 (53.2%) had Crohn's disease and 275 (46.8%) had Ulcerative Colitis. Infliximab (IFX) was given to 93 patients (median 912 days; range 20-5273); at endpoint, 39 (42.4%) remained on IFX. Adalimumab (ADA) was used by 165 patients (median 1051 days; range 48-4458); 87 (52.4%) remained at endpoint. Vedolizumab (VDZ) included 116 patients (median 717 days; range 0-2204); 75 (64.4%) remained at endpoint. Ustekinumab (UST) was given to 62 patients (median 660 days; range 50-1399); 51 (83.6%) remained at endpoint. Some patients were exposed to multiple biologicals, contributing to smaller numbers for newer drugs. When evaluated as a first-line biological, UST (median 787 days) and VDZ (median 756.5 days) had the shortest durations, while TNF-α blockers (ADA, IFX) showed the greatest resistance as first-line therapy. <b>Conclusions:</b> Most patients stayed on their initial therapy after induction and at 1 year. These findings support the sustained use of established biological therapies as cost-effective, steroid-sparing options even after IL-23 approval and may inform patient counseling and long-term pharmacoeconomic considerations.