Long‐Term Real‐World Evaluation of Tofacitinib's Effectiveness and Safety in Japan: Insights Into Optimal Timing for Dose Reduction

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Aims Tofacitinib (TOF), an oral pan‐Janus kinase (JAK) inhibitor, is a therapeutic option for moderate to severe ulcerative colitis (UC). While short‐term efficacy has been reported, its long‐term real‐world outcomes—particularly in Asian populations—and optimal dose reduction timing are incompletely understood. Methods and Results This single‐center, retrospective study included 63 patients with UC treated with TOF between October 2018 and April 2025. Clinical outcomes—response, remission, steroid‐free remission, and adverse events—were assessed at Weeks 26, 52, and 104. The impact of dose reduction (20–10 mg/day) was analyzed, focusing on endoscopic mucosal healing (Mayo endoscopic subscore 0–1). At Week 26, clinical response and remission rates were 63% and 53%, respectively; 43% of patients achieved steroid‐free remission by Week 52, and 41% maintained it at Week 104. Early responders were associated with treatment efficacy in a lower partial Mayo score (OR = 1.724, 95% CI: 0.994–2.988, p = 0.052). Among 26 patients with dose reduction, relapse occurred in 5.6% with mucosal healing versus 62.5% without. Significant factors associated with relapse/exacerbation were TOF dose reduction based on clinical remission alone without endoscopic confirmation ( p = 0.003, OR = 5.26) and disease duration ( p = 0.019, OR = 0.86). Adverse events were infrequent and manageable, with no malignancies or deaths reported. Conclusion TOF demonstrated sustained effectiveness and safety in UC. Mucosal healing was strongly associated with successful dose de‐escalation, representing a key treatment target. These findings support treat‐to‐target strategies incorporating endoscopic assessment to guide TOF dose reduction.