P022 Biologic Therapy and Therapeutic Drug Monitoring in Patients With Inflammatory Bowel Disease and Primary Sclerosing Cholangitis

BACKGROUND: Primary sclerosing cholangitis (PSC) is associated with inflammatory bowel disease (IBD). Patients with concomitant PSC-IBD are at higher risk for IBD-related complications including dysplasia and malignancy, however the typical clinical IBD course is less severe. The aim of this study was to identify the prevalence of biologic use and therapeutic drug monitoring (TDM) in a cohort of PSC-IBD patients. METHODS: Retrospective analysis of patients with PSC-IBD on biologic therapy who underwent TDM from Jan. 2018 to Aug. 2020 at the University of Virginia. Demographic data including age, disease duration, and comorbidities were recorded. IBD categorizations were recorded according to the Montreal Classification. Treatment outcomes including therapy changes after TDM were obtained. RESULTS: A total of 157 patients with PSC-IBD were identified. Of these, 29 patients (19%) were treated with biologic therapy during the study period. 13 patients underwent reactive TDM due to primary or secondary loss of response and one patient underwent proactive TDM during the study period. Median duration of IBD in this group was 9 years, and the median duration of concomitant PSC-IBD was 5.8 years. 20 TDM tests were obtained in these 14 total patients. Sub-therapeutic drug levels were found in 12 tests among 8 patients, and 3 showed detectable anti-drug antibodies. 8 showed appropriate trough levels. TDM resulted in a change to IBD therapy (i.e., dose escalation, change in biologic therapy used, or addition of IBD medication) in 17 out of 20 tests. CONCLUSION: Herein we describe epidemiologic data of biologic use in PSC-IBD patients at an academic center. PSC-IBD classically follows a less severe clinical presentation and course. However, our study demonstrates that a subset of PSC-IBD patients exist which require biologic therapy and follow a more refractory clinical trajectory. In this subset, TDM showed a high incidence of sub-therapeutic trough levels and anti-drug antibodies, leading to a change in therapy in 85% of TDM instances. Larger studies are recommended to better understand this unique subset of PSC-IBD patients.