Impact of Concomitant Thiopurine on the Efficacy and Safety of Filgotinib in Patients with Ulcerative Colitis: Post Hoc Analysis of the Phase 2b/3 SELECTION Study

Background and Aims: SELECTION is the first study to assess the impact of concomitant thiopurine and other immunomodulator [IM] use on the efficacy and safety of a Janus kinase inhibitor, filgotinib, in patients with ulcerative colitis. Methods: Data from the phase 2b/3 SELECTION study were used for this post hoc analysis. Patients were randomised [2:2:1] to two induction studies [biologic-naive, biologic-experienced] to filgotinib 200 mg, 100 mg, or placebo. At Week 10, patients receiving filgotinib were re-randomised [2:1] to continue filgotinib or to switch to placebo until Week 58 [maintenance]. Outcomes were compared between subgroups with and without concomitant IM use. Results: At Week 10, similar proportions of patients in the +IM and -IM groups treated with filgotinib 200 mg achieved Mayo Clinic Score [MCS] response [biologic-naive: 65.8% vs 66.9%; biologic-experienced: 61.3% vs 50.5%] and clinical remission [biologic-naive: 26.0% vs 26.2%; biologic-experienced: 11.3% vs 11.5%]. At Week 58, similar proportion of patients in the +IM and -IM groups treated with filgotinib 200 mg achieved MCS response [biologic-naive: 74.2% vs 75.0%; biologic-experienced: 45.5% vs 61.4%] and clinical remission [biologic-naive: 51.6% vs 47.4%; biologic-experienced: 22.7% vs 24.3%]. The probability of protocol-specified disease worsening during the maintenance study in patients treated with filgotinib 200 mg did not differ between +IM and -IM groups [p=0.6700]. No differences were observed in the incidences of adverse events between +IM and -IM groups in the induction/maintenance studies. Conclusions: The efficacy and safety profiles of filgotinib treatment in SELECTION did not differ with or without concomitant IM use.