Relationship between Ustekinumab trough concentrations and clinical, biochemical and endoscopic outcomes in Crohn's disease: A multi-center nationwide retrospective study (TARGET STUDY).

Ustekinumab has been shown to be effective in inducing and maintain clinical and endoscopic remission in Crohn disease (CD). We aim to assess whether ustekinumab trough levels are associated with improved outcomes in CD in real-life. We recruited patients with CD who were treated with ustekinumab for at least 6 months from January 2017 to June 2023. Patients received ustekinumab 6 mg/kg intravenous induction followed by 90 mg every 4-, 8-, or 12-weeks during maintenance were included. We assessed clinical, biochemical, and endoscopic outcomes. Trough concentrations of ustekinumab that were taken from week 42 to week 52 were measured. Primary outcome was to evaluate the relationship between ustekinumab trough concentrations and clinical remission, biochemical normalization, and endoscopic remission. Logistic regression was conducted to assess outcomes. A total of 137 patients with CD, median age of 32 years and 83 (60.6%) males. The median serum levels of ustekinumab measured was 7.2 mcg/mL (interquartile range [IQR] 3.1-9.6). Using Spearman correlation analysis, a strong negative correlation was observed between ustekinumab drug levels and simple endoscopic score (SES-CD) (r = -0.464, P < .001). Additionally, ustekinumab drug levels demonstrated substantial negative correlations with disease severity measured by Harvey-Bradshaw index (HBI) score (r = -0.582, P < .001), C-Reactive Protein (CRP) levels (r = -0.598, P < .001) and fecal calprotectin (FC) levels (r = -0.529, P < .001). A multivariable analysis adjusted for age, sex and body mass index (BMI) showed a significant association between ustekinumab serum drug levels and predefined outcomes. Ustekinumab serum drug level above 4.5 mcg/mL was associated with 24% increase in the likelihood of having an SES-CD score <3 (OR 1.24, confidence interval [CI] 1.12-1.37, P value < .001), 44% more likely to achieve HBI score <5 (OR 1.44, CI 1.26-1.65, P value < .001), 52% higher likelihood of CRP more than 10 (OR 1.52, CI 1.31-1.77, P < .001), and 42% increased likelihood of FC more than 250 (OR 1.42, CI 1.24-1.62, P < .001). Ustekinumab trough concentrations above 4.5 mcg/mL were associated with clinical, biochemical and endoscopic remission in CD. Prospective data is warranted to confirm these findings.