Abstract Background Filgotinib, a selective Janus kinase 1 (JAK1) inhibitor, is an oral small-molecule therapy that reduces cytokine-mediated inflammation by inhibiting JAK-1 dependant signalling pathways, including those involving interleukin-6 (IL-6) and type I interferons1. While clinical trials support its safety and efficacy, real-world data, particularly in the UK and Ireland, are limited. Methods A retrospective cohort study was conducted at the Ulster Hospital, Northern Ireland, the largest centre within the South Eastern Health and Social Care Trust. Patients with active ulcerative colitis (UC) who initiated filgotinib between November 2022 to March 2025 were identified via electronic health records. Demographics, disease duration, prior therapies, and clinical/biochemical markers were collected at baseline and approximately 12 weeks post-treatment. Parameters analysed included Partial Mayo Score (PMS), C-reactive protein (CRP), faecal calprotectin (FC), and serum albumin. Paired t-tests compared changes from baseline for each parameter. Results Forty-six adult patients were included (24 males, 22 females; median age 35.5 years, range 19–73). The median follow-up duration was 10 months, with a range of 4 to 29 months. The median disease duration was 7 years, and the median duration of filgotinib therapy was 9 months, with a range of 1 to 29 months. 23 patients (50%) were biologic-naïve and 23 (50%) were receiving biologic therapy, including 10 (21.7%) who had previously received ≥2 biologics. Based on the Partial Mayo Score (PMS; n = 40), remission (Partial Mayo Score ≤2) was achieved in 19 biologic-naïve patients and 13 receiving biologics. PMS significantly improved from a mean of 5 at baseline to 1.7 at 12 weeks; with clinical remission increased from 7 patients (17.5%) at baseline, to 31 patients (77.5%) at week 12 post-filgotinib treatment. CRP (n = 44) and serum albumin (n = 43) showed non-significant trends (p = 0.33 and p = 0.81, respectively). Faecal calprotectin (n = 10) decreased significantly from 1260 µg/g to 218 µg/g (p = 0.026). Filgotinib was well tolerated; 34 (73.9%) reported no side effects, with mild gastrointestinal symptoms such as nausea or abdominal discomfort, in the remainder. No serious adverse events occurred during treatment. At week 12, 42 (91%) patients continued treatment and 4 patients (8.7%) discontinued. Conclusion This real-world study provides the first evidence from Northern Ireland supporting the use of filgotinib in UC. Filgotinib was associated with significant improvements in Partial Mayo Score and faecal calprotectin, favourable safety, and high treatment persistence, consistent with clinical trial findings and supporting its effectiveness and safety in practice. Reference: 1. Traves PG, Murray B, Campigotto F, Galien R, Meng A, Di Paolo JA. JAK selectivity and the implications for clinical inhibition of pharmacodynamic cytokine signalling by filgotinib, upadacitinib, tofacitinib and baricitinib. Ann Rheum Dis. 2021;80(7):865-875. doi:10.1136/annrheumdis-2020-219012 Conflict of interest: Woo Ling, Kimberlee: Nil Walsh, Caolan: Nil Tham, Tony: Nil Maybin, Nicola: Nil
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