JAK1-preferential inhibition in refractory inflammatory bowel disease: reframing upadacitinib as a strategy for rapid...

Inflammatory bowel disease (IBD) management has moved from symptom control toward treat-to-target strategies, yet many patients with ulcerative colitis or Crohn's disease remain difficult to treat after primary non-response, secondary loss of response, or intolerance to advanced therapy. Upadacitinib, an oral Janus kinase 1 (JAK1)-preferential inhibitor, has shown clinically meaningful efficacy in both ulcerative colitis and Crohn's disease, including biologic-experienced populations. In this Perspective, we propose rapid immune recalibration as a hypothesis-generating clinical model for interpreting rapid inflammatory control following JAK1-preferential inhibition in selected patients with inflammation-dominant refractory IBD, rather than as an established biological mechanism or evidence of a durable immune reset. Recalibration is defined here as an early pharmacologically induced shift in the intensity and balance of convergent cytokine signaling, not as immune homeostasis restoration, mucosal healing, transmural repair, fibrosis reversal, or proven disease modification. We distinguish established clinical evidence from mechanistic rationale and from unvalidated downstream hypotheses, including barrier stabilization, microbiome change, anti-fibrotic potential, and biomarker-guided positioning. We also outline measurable clinical criteria, feasible biomarkers, exploratory translational endpoints, and safety boundaries that should guide future testing of this framework. This more bounded interpretation may help inform future efforts to move refractory IBD treatment from empirical drug switching toward mechanism-informed therapeutic choice without overstating the current evidence.