SummaryBackgroundFilgotinib, an oral, once‐daily, Janus kinase 1 preferential inhibitor, is an approved treatment for moderately to severely active ulcerative colitis.AimsThe aim of this study is to assess the safety and efficacy of continued filgotinib therapy over ~4 years in the long‐term extension of the phase 2b/3 SELECTION trial (SELECTIONLTE; NCT02914535).MethodsIn this interim analysis of SELECTIONLTE, SELECTION completers (week 10 responders to filgotinib who completed the maintenance study) continued their assigned treatment (double‐blind filgotinib 200 mg [FIL200] or filgotinib 100 mg) and SELECTION week 10 non‐responders received open‐label FIL200. We assessed safety by adverse events (AEs), and efficacy by partial Mayo Clinic Score (pMCS), inflammatory biomarkers and health‐related quality of life (HRQoL). We compared safety and efficacy between achievers and non‐achievers of a multi‐component endpoint, comprehensive disease control (CDC), comprising symptomatic, endoscopic, inflammatory biomarker and HRQoL improvements.ResultsData for completers (n = 250) and non‐responders (n = 372) were reported for ≤202 weeks. AE occurrences were low and consistent with previous analyses. The as‐observed proportion of FIL200‐treated patients in pMCS, biomarker and HRQoL remission during SELECTIONLTE remained high among completers (week 144: 80.0%, 86.4% and 86.0%, respectively) and increased among non‐responders (week 192: 62.1%, 76.7% and 59.3%, respectively). Significantly higher proportions of CDC achievers at SELECTION week 58 achieved pMCS, IBDQ and corticosteroid‐free pMCS remission than non‐achievers, up to LTE week 96.ConclusionsFilgotinib induced and maintained symptomatic remission and improved HRQoL over 4 years. Safety results showed a proven long‐term benefit–risk profile. FIL200‐treated CDC achievers had better long‐term outcomes than non‐achievers.