A Study of Mirikizumab (LY3074828) in Participants With Ulcerative Colitis

Inclusion Criteria: * Participants must have a diagnosis of UC for at least 3 months prior to baseline * Participants must have a confirmed diagnosis of moderately or severely active UC, as assessed by the modified Mayo score (MMS) * Participants must have demonstrated an inadequate response to, a loss of response to, or an intolerance to conventional or to biologic therapy for UC * Participants must, if female, meet the contraception requirements Exclusion Criteria: * Participants must not have a current diagnosis of Crohn's disease or inflammatory bowel disease-unclassified (indeterminate colitis) * Participants must not have had a previous colectomy * Participants must not have current evidence of toxic megacolon * Participants must not have prior exposure to anti-IL-23p19 antibodies (e.g. risankizumab, brazikumab, guselkumab or tildrakizumab), vedolizumab, or natalizumab * Participants must not have prior clinical failure or intolerance to anti-IL12p40 antibodies (e.g. ustekinumab), anti-integrin antibodies other than vedolizumab and natalizumab (e.g. etrolizumab) or anti-integrin ligand antibodies (e.g. ontamalimab) within 4 weeks prior to screening endoscopy