P0922 Usefulness of Ustekinumab levels in clinical practice: a single center experience
Authors: Garcia De La Filia Molina I , Mesonero Gismero F , López Cardona J , Fernández Fernández C , Roy Ariño G , Gramage Caro T , Albillos Martínez A , López San Román A 
Published: January 2025

Abstract

Background
Drug monitoring is a valuable resource in Inflammatory Bowel Disease (IBD) management. However, evidence regarding Ustekinumab (UTK) utility in clinical practice is scarce as the optimal therapeutic levels and strategy after their determination have not been clearly established so far.

Methods
Single-center retrospective study of IBD patients treated with UTK in whom drug levels were measured during maintenance, between October 2021-August 2024. UTK dose was defined as standard: 90 mg subcutaneously (sc)/8-12 weeks or intensified: 90 mg sc/&lt;8 weeks or 130 mg intravenously (iv)/any frequency. UTK levels were measured using ELISA technique (μg/mL). Since there is no specific protocol in our center, patients were divided into two level determination strategies: reactive (patient with clinical and/or biochemical activity) and proactive (remission patients). The endpoint was to evaluate the utility of UTK levels in guiding therapeutic decisions. To guide our clinical decisions, we have based on the recommendations from the GETECCU 2024 consensus document.

Results
Seventy-four patients were included (Table 1). They had been on UTK therapy for a mean of 42 (±21) months (35% with intensified dose: 81% sc/19% iv). Level strategy was reactive in 74% (disease activity: 20% clinical, 22% biochemical, 58% both) and proactive in 26%. In reactive strategy, UTK was intensified in 65% of cases (56% with UTK level &lt;1.5, 36% 1-3); unchanged in 20%, with UTK level &gt;1.5 in 82% of them, considering acceptable disease control with therapeutic levels; and discontinued in 15%, all with UTK level &gt;3, assuming that intensification would not provide benefit. Among patients with UTK intensification, response/remission was achieved in 39%/42%, after a median of 132 (110-172) days. In the proactive group, 68% of cases were on intensified UTK, measuring levels to assess whether UTK could be de-escalated. After level determination, UTK dose was modified in 58%: spaced out in 53% (all with UTK level &gt;3) and intensified in 5.3% (UTK level &lt;1.5) (Figure 1). Overall, level determination had a clinical impact in 70% of patients, influencing the therapeutic decision in 75% of reactive strategy and guiding the maintenance dose adjustment in 58% of proactive strategy. At the end of the study, 82% of patients remained on UTK (95%/78% on proactive/reactive strategy), after a median follow-up of 12 (5-28.5) months.

Conclusion
Drug level determination is a useful tool in optimizing UTK therapy in IBD, both guiding clinical decisions in active disease and monitoring during remission. It allows candidate selection for intensification and de-escalation, maintenance or treatment discontinuation.

References
Rodríguez-Moranta F et al. Therapeutic drug monitoring in inflammatory bowel diseases. Position statement of the Spanish Working Group on Crohn’s Disease and Ulcerative Colitis. Gastroenterología y Hepatología 2024.