Peficitinib, an Oral Janus Kinase Inhibitor, in Moderate-to-severe Ulcerative Colitis: Results From a Randomised, Phase 2 Study

Background and Aims: Janus kinase [JAK] inhibitors have shown efficacy in ulcerative colitis [UC]. We studied the dose-response, efficacy, and safety of peficitinib, an oral JAK inhibitor, in patients with moderate-to-severe UC. Methods: In this Phase 2b, dose-ranging trial, we evaluated peficitinib at 25 mg once daily [o.d.], 75 mg o.d., 150 mg o.d., and 75 mg twice daily versus placebo for efficacy and safety in 219 patients with moderate-to-severe UC. The primary outcome was peficitinib dose-response at Week 8, with response assessed using Mayo score change from baseline. Secondary endpoints were clinical response, clinical remission, mucosal healing, change from baseline in Inflammatory Bowel Disease Questionnaire [IBDQ], and normalisation of inflammatory biomarkers at Week 8; other secondary endpoints were treatment response through Week 16 and through Week 32 for patients in clinical response at Week 8. Safety was assessed through Week 36 or 4 weeks after the last dose. Results: A statistically significant peficitinib dose-response was not demonstrated at Week 8, although a numerically greater proportion of patients receiving peficitinib >= 75 mg o.d. achieved clinical response, remission, and mucosal healing at Week 8, supported by IBDQ improvement and inflammatory biomarker normalisation. Treatment-emergent adverse event [TEAE] rates reported through Week 8 and the final safety visit were higher in the combined peficitinib group than in the placebo group; patients receiving doses of >= 75 mg o.d. peficitinib reported TEAEs more frequently. Conclusions: No dose-response in patients with moderate-to-severe UC was demonstrated with peficitinib, but evidence of efficacy was suggested at doses >= 75 mg o.d. The safety profile of peficitinib was consistent with current information.