Ustekinumab trough concentration affects clinical and endoscopic outcomes in patients with refractory Crohn's disease: a Chinese real-world study.

<bold>Background: </bold>Ustekinumab (UST), a newly-used biologic targeting p40 subunit of IL12 and IL23 in China, exerts a confirmed therapeutic effect on the induction and maintenance therapies for refractory Crohn's disease (CD). Therapeutic drug monitoring based on trough and antibody concentration is of core importance when treating patients who lose response to UST. We aimed to analyze the UST exposure-response relationship in CD treatment in the real-world setting.<bold>Methods: </bold>We retrospectively enrolled patients with CD who received UST between March 1, 2020 and May 31, 2021, at the inflammatory bowel disease (IBD) center of the Sun Yat-Sun Affiliated Sixth Hospital. Baseline characteristic information, biomarker examination, clinical outcomes determined by the Crohn's disease activity index (CDAI), and endoscopic outcomes evaluated using a simple endoscopic score for Crohn's disease (SES-CD) at week 16/20 were collected. The optimal UST cut-off trough concentration was identified using receiver operating characteristic curve (ROC) analysis.<bold>Results: </bold>Nineteen eligible patients were included in the study, the mean age was 29.1 ± 9.1 years and the mean disease duration was 5.5 ± 4.7 years. At the initiation of the study, 89.5% of the patients had been exposed to prior biologics, 42.1% had previous CD-related surgeries, and 52.6% had perianal diseases. At week 16/20 after the UST initiation, clinical response, clinical remission, endoscopic response, and endoscopic remission were 89.5%, 84.2%, 42.2%, and 73.7%, respectively. The cut-off optimal trough concentration for UST was 1.12 μg/mL, as determined by the ROC with an area under the curve (AUC) of 0.78, sensitivity of 87.5%, and specificity of 72.7%. Patients with a UST trough concentration > 1.12 μg/mL had a significantly higher rate of endoscopic remission than those without (70.0% vs. 11.1%, P = 0.02).<bold>Conclusions: </bold>UST is an effective therapeutic option for refractory CD treatment. A UST trough concentration above 1.12 μg/mL was associated with endoscopic remission at week 16/20 after UST initiation. Trial registration This study was approved and retrospectively registered by the Ethics Committee of Sun Yat-Sen University (2021ZSLYEC-066, March 29, 2021) and the Clinical Trial Registry (NCT04923100, June 10, 2021). [ABSTRACT FROM AUTHOR]