RecruitingPhase 2Drug trialProof of Concept Study Evaluating the Efficacy and Safety of ATH-063 Treatment in Patients With Relapsed/Refractory Moderately to Severely Active Ulcerative Colitis (UC)The primary objective of this trial is to evaluate the clinical efficacy of ATH-063 in participants with biologic/advanced therapy relapsed/refractory moderately to severely active UC.