The trial was terminated secondary to a business decision, the original scientific question rendered moot by the external scientific community.

The purpose of this study is to evaluate if study drug mirikizumab is safe and effective compared to vedolizumab and placebo in participants with moderately to severely active ulcerative colitis (UC).

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

Anonymized individual patient level data will be provided in a secure access environment upon approval of a research proposal and a signed data sharing agreement.

Data are available 6 months after the primary publication and approval of the indication studied in the US and EU, whichever is later. Data will be indefinitely available for requesting.

A research proposal must be approved by an independent review panel and researchers must sign a data sharing agreement.