Proactive therapeutic drug monitoring and vedolizumab dose optimization in children with inflammatory bowel disease

Objectives: Therapeutic drug monitoring (TDM) and dose optimization have been shown to improve clinical outcomes with antitumor necrosis factor and recent studies in adults suggest an exposure-response relationship with drug levels associated with improved clinical outcomes. However, these levels are not universally recognized as therapeutic targets for vedolizumab dosing. We aimed to assess the impact of a TDM quality improvement (QI) initiative on 52-week clinical outcomes and describe proactively obtained vedolizumab levels during the induction period in children with inflammatory bowel disease (IBD).

Methods: A QI initiative to proactively obtain TDM levels at Week 6 was implemented in 2019. A retrospective review of pediatric patients with IBD treated with vedolizumab from 2018 to 2022 was performed. Baseline demographic data, medication dosing details, disease characteristics, lab results, and 12-month clinical outcomes were recorded. For this study, we defined therapeutic target levels (>20 μg/mL at Week 6 and >12 μg/mL during maintenance) based on existing data correlating these levels with improved clinical outcomes.

Results: Fifty-nine patients (31 Crohn disease [CD], 28 ulcerative colitis [UC]/indeterminate colitis [IC]) were included in the study. In total, 68% (40/59) of patients had vedolizumab levels at Week 6 and 90% (53/59) had levels drawn at Week 6 or 14. Thirty-five percent of Week 6 trough levels were below our defined target of 20 μg/mL. Fifty-two of 59 patients had available data at 52 weeks. Over 80% (42/52) of patients remained on vedolizumab 52 weeks after initiation (CD 79% [23/29], UC/IC 83% [19/23]). Sixty-two percent (26/42) of patients that remained on vedolizumab at 52 weeks were treated with an intensified dosing interval of <8 weeks. Thirty-one of these 42 (74%) were in clinical remission (CR) rate at 52 weeks with 29/42 (69%) in corticosteroid-free remission. The CR rate for the entire cohort including those who discontinued therapy due to a lack of efficacy before 52 weeks was 60% (31/52).

Conclusion: Proactive TDM and early dose optimization with vedolizumab may improve drug durability and clinical outcomes in pediatric patients with IBD.