Upadacitinib in Colonic Crohn's Disease: A Narrative Review of Mechanistic Rationale, Clinical Trial Evidence, and Real-World Outcomes.

Crohn's disease (CD) is a chronic inflammatory bowel disorder with colonic involvement in a substantial proportion of patients, often associated with increased symptom burden and therapeutic complexity. Upadacitinib, a selective Janus kinase 1 (JAK1) inhibitor, has emerged as an effective oral therapy for moderate-to-severe CD, including patients with colonic-predominant disease. This narrative review synthesizes evidence from phase 2 and 3 randomized controlled trials, post-hoc subgroup analyses, long-term extension studies, and real-world observational cohorts evaluating the efficacy and safety of upadacitinib in CD with colonic involvement. Across pivotal trials, induction therapy demonstrated superior rates of clinical remission (approximately 39-50% versus 21-29% with placebo), significant endoscopic response, and rapid symptom improvement. Maintenance therapy sustained both clinical and endoscopic outcomes through one year and beyond. Real-world studies corroborate effectiveness in highly treatment-experienced populations, although heterogeneity in study design limits causal inference. The safety profile is consistent with known JAK inhibitor class effects, with infections-particularly herpes zoster-requiring appropriate risk mitigation. Pharmacogenetic predictors of response to upadacitinib remain undefined, representing an important area for future research. Overall, upadacitinib constitutes a valuable therapeutic option for patients with refractory colonic CD, while comparative effectiveness and precision-medicine strategies warrant further investigation.