RecruitingPhase 3Drug trialComparison of Medical RESCUE Strategies for Patients With Steroid-refractory Acute Severe Ulcerative ColitisThis study aims to examine patients with acute severe UC who are refractory to intravenous corticosteroids and determine whether a strategy of using upadacitinib first followed by infliximab in upadacitinib non-responders is non-inferior to conventional management with infliximab only.