Inclusion Criteria:  Participants from originating studies (I6T-MC-AMBU [NCT04004611]) who should, in the opinion of the investigator, derive clinical benefit from further treatment with mirikizumab Participants from prior studies who have had at least one study drug administration and have not had early termination of study drug. Female participants must agree to contraception requirements.  Exclusion Criteria:  Participants must not have developed a new condition, including cancer in the originator study. Participants must not have any important infections including, but not limited to, hepatitis B, hepatitis C, HIV/AIDS, and active tuberculosis (TB) during either originator study. Participants must not have received surgery for UC in the originator study or are likely to require surgery for treatment of UC during the study. Participants must not require parenteral nutrition delivered by central vein and/or central venous catheter for venous access.