P0571Wash-out period in the transition from biologics to small molecules has no impact on safety in IBD: a retrospective cohort study

Abstract Background In clinical trials, a wash-out period between discontinuation of an advanced therapy and initiation of another is typically required to ensure accurate assessment of treatment efficacy and to minimize the risk of adverse events. However, real-world data on the safety implications and clinical necessity of such wash-out intervals remain limited. We aimed to assess the safety of transitioning from biologics to small molecules in patients with IBD, with analyses stratified according to short versus delayed wash-out periods. Methods This retrospective study included patients with IBD who underwent transition from biologics to small molecules between January 2021 and April 2025 at a tertiary referral center. Patients were categorized as short (≤30 days) or delayed (30 days) transition. The primary outcomes were the incidence of any infections at 1,3 and 6 months after the transition. Results In total 100 patients (51% female, with a median age 39,36 years ± 13,72) with IBD were included (82% UC patients). The most frequent therapeutic switches were from anti-TNF to JAKi (33%), from ustekinumab to JAKi (28%), from vedolizumab to JAKi (27%) from selective IL23 inhibitors to JAKi (8%), from anti-TNF to S1Pr modulators (3%), from vedolizumab to S1Pr modulators (1%). Two-thirds of the switches (68%) were justified by secondary non response. Patients were classified as early (≤30 days, n = 55) or late switch (30 days, n = 45). No statistically significant difference was observed in the rate of infectious adverse events between patients with an early and a late switch at 1 month (χ²(1) = 0.73, p = 0.39, Cramer’s V = 0.00, 95% CI 0.00, 0.27, N = 98), 3 months (χ²(1) = 0.38, p = 0.54, Cramer’s V = 0.00, 95% CI 0.00, 0.25, N = 88), 6 months (χ²(1) = 0.35, p = 0.56, Cramer’s V = 0.00, 95% CI 0.00, 0.27, N = 74), and 12 months (χ²(1) = 0.02, p = 0.90, Cramer’s V = 0.00, 95% CI 0.00, 0.19, N = 55). Similarly, no statistically significant difference was observed in the rate of non-infectious adverse events between early and late switch at 1 month (χ²(1) = 1.85, p = 0.17, Cramer’s V = 0.09, 95% CI 0.00, 0.32, N = 99), 3 months (χ²(1) = 0.03, p = 0.87, Cramer’s V = 0.00, 95% CI 0.00, 0.16, N = 88), 6 months (χ²(1) = 2.36, p = 0.12, Cramer’s V = 0.14, 95% CI 0.00, 0.40, N = 72), and 12 months (χ²(1) = 1.10, p = 0.29, Cramer’s V = 0.04, 95% CI 0.00, 0.39, N = 55). Conclusion In this retrospective study no statistically significant differences were observed in the incidence of infectious or non-infectious adverse events between early and late switch groups at 1, 3, 6, and 12 months, indicating that the timing of the switch from biologics to small molecules did not impact safety outcomes. Conflict of interest: Dr. Fanizzi, Fabrizio: No conflict of interest D’Amico, Ferdinando: Grant: ECCO fellowship grant 2020 ECCO grant 2021 Personal Fees: F D’Amico has served as a speaker for Abbvie, Alfasigma, Ferring, Lilly, Sandoz, Janssen, Fresenius Kabi, Galapagos, Giuliani, MSD, Pfizer, Takeda, Tillotts, and Omega Pharma he also served as an advisory board member for Abbvie, AnaptysBio, Ferring, Fresenius Kabi, Galapagos, Janssen, Lilly, MSD, Takeda, and Nestlè. Zilli, Alessandra: Personal Fees: Speaking and consulting fees from Tillotts, Galapagos, Abbvie, Takeda, Janssen, Alfasigma, Sandoz, Lilly, Pfizer Solitano, Virginia: Speaker’s fees from Pfizer, Takeda, Giuliani, Tillotts Pharma consulting fees from J & J travel grant from Abbvie Furfaro, Federica: Grant: IG-IBD Personal Fees: Pfizer, Biogen, J&J, Abbvie, Amgen, Janssen Parigi, Tommaso Lorenzo: Tommaso L Parigi declares no relevant conflicts of interest Allocca, Mariangela: Personal Fees: consulting fees from Nikkiso Europe, Mundipharma, Janssen, Abbvie, Pfizer, Ferring, Galapagos, Sandoz, Lilly and Alfasigma Peyrin-Biroulet, Laurent: CONSULTING Abbvie, Abivax, Adacyte, Alimentiv, Alfasigma, Amgen, Apini, Banook, BMS, Celltrion, Enthera, Ferring, Fresenius Kabi, Galapagos, Genentech, Gilead, Iterative Health, Janssen, Lilly, LifeMine, Medac, Morphic, MSD, Nordic Pharma, Novartis, Oncodesign Precision Medicine, ONO Pharma, OSE Immunotherapeuthics, Par’ Immune, Pfizer, Prometheus, Roche, Roivant, Samsung, Sandoz, Sanofi, Sorriso, Spyre, Takeda, Teva, ThirtyfiveBio, Tillots, Vectivbio, Vedanta, Ventyx. LECTURE Abbvie, Alfasigma, Amgen, Biogen, Celltrion, Ferring, Galapagos, Genentech, Gilead, Iterative Health, Janssen, Lilly, Medac, MSD, Nordic Pharma, Pfizer, Sandoz, Takeda, Tillots Massimino, Luca: No conflict of interest Jairath, Vipul: Consulting Fees: Abbvie, Alimentiv, Amgen, Anaptys Bio, Asahi Kasei, Asieris, Astra Zeneca, Attovia, Blackbird Labs, BMS, Boehringer Ingleheim, Biomebank, Caldera, Calluna, Catalytic Health, Celltrion, Ensho, Enthera, Exeliome Biosciences, Ferring, Fresenius Kabi, Gilead, Granite Bio, GSK, Janssen, Lilly, Merck, Mountainfield, MRM Health, Nxera, Organon, OSE Immunotherapeutics, Pendopharm, Pioneering Medicine, Pfizer, Prometheus, Roche/Genentech, Sanofi, SCOPE, Shattuck Labs, Sorriso, Spyre, Synedgen, Takeda, Teva, Tillotts, Union Therapeutics, Ventus, Ventyx, Vividion, Xencor, Zealand Pharma. Danese, Silvio: Personal Fees: AbbVie, Alimentiv, Allergan, Amgen, Applied Molecular Transport, AstraZeneca, Athos Therapeutics, Biogen, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Celltrion, Dr Falk Pharma, Eli Lilly, Enthera, Ferring Pharmaceuticals Inc., Gilead, Hospira, Inotrem, Janssen, Johnson & Johnson, Morphic, MSD, Mundipharma, Mylan, Pfizer, Roche, Sandoz, Sublimity Therapeutics, Takeda, Teladoc Health, TiGenix, UCB Inc., Vial, Vifor Lecture fees from Abbvie, Amgen, Ferring Pharmaceuticals Inc., Gilead, Janssen, Mylan, Pfizer, Takeda