P629 JAK inhibitor safety in Inflammatory Bowel Disease: real-world data comparing the effect of JAK inhibitors on blood parameters and their clinical significance

Abstract Background Janus kinase inhibitors (JAKi) licensed for the treatment of inflammatory bowel disease (IBD) now include tofacitinib, upadacitinib and filgotinib. JAKi are known to cause abnormalities in a multitude of blood tests. However, whether there are differences in their effects in a ‘real-world’ setting is not known. Methods Blood test results for 118 patients treated with a JAKi were collected. A total of 13 parameters known to be affected were included. Percentage change at 12 and 24 weeks from baseline was calculated and compared amongst the different JAKi. The difference between the proportion of patients with abnormal results at each time-point was also reviewed. Results The JAKi breakdown included: tofacitinib-64, upadacitinib-35, filgotinib-18. JAKi treatment was associated with a significant rise in cholesterol, bilirubin, ALP and AST at 12 and 24 weeks (table 1), while rises in triglyceride and LDL cholesterol, and haemoglobin reduction were only apparent at 24 weeks. Other parameters showed transient or non-significant changes. Individual analysis of each parameter highlighted only two significant differences amongst JAKi: upadacitinib significantly reduced WCC (p=0.048) and neutrophil count (p=0.044) within the group at 24 weeks, and when directly compared to tofacitinib (p=0.047). However, no patients were neutropenic at 24 weeks and only 5 patients had a low WCC (upadacitinib: 3, tofacitinib: 2, filgotinib: 1). As per Common Terminology Criteria for Adverse Events (CTCAE), adverse events (AEs) in these parameters were low despite the significant percentage change in multiple variables. 1 patient (1.1%) was found to be anaemic (Hb