LY4268989 (MORF-057) Co-Administered With Mirikizumab in Adults With Moderately to Severely Active Ulcerative Colitis:

Inclusion Criteria:

• Have had an established diagnosis of ulcerative colitis (UC) of ≥3 months in beforebaseline, which includes endoscopic evidence of UC and a histopathology report thatsupports a diagnosis of UC

• Have moderately to severely active UC as defined by a Modified Mayo Score (mMS) of 5to 9 with an Endoscopic Score (ES) ≥2 confirmed by central reader and rectalbleeding (RB) ≥1, with endoscopy performed within 21 days before baseline

• Participants with greater than 8 years of UC symptoms have documented evidence ofhaving had a surveillance colonoscopy within 1 year, or according to local countryor regional medical guidelines, to evaluate for polyps, dysplasia, or malignancy,prior to randomization

• Are up-to-date on colorectal cancer surveillance per local society guidelines

• Have an inadequate response to, loss of response to, or intolerance to at least 1 ofthe medications:

• Conventional-failed participants: Participants who have had an inadequate responseto or a loss of response to or are intolerant to at least 1 of the followingmedications: corticosteroids or immunomodulators (Does not apply to US)

NOTE: After the interim analysis, participants with inadequate response, loss of response, or intolerance to conventional UC therapy without prior exposure to biologics may be enrolled if deemed appropriate (Applies to the US)

• Advanced therapy-failed participants: Participants who have an inadequate responseto or a loss of response to, or are intolerant to advanced therapy for UC, definedas:

• a biologic or biosimilar medication such as anti-tumor necrosis factor (anti-TNF) antibodies or anti-interleukin antibodies (IL-12/23, or IL-23p19),except for

• mirikizumab.

• Janus kinase inhibitors (JAK) such as filgotinib, tofacitinib, or upadacitinib

• sphingosine 1-phosphate receptor 1 inhibitors (S1PR) such as etrasimod orozanimod

Exclusion Criteria:

• Have a current diagnosis of

• Crohn's disease

• Inflammatory Bowel Disease (IBD) unclassified (formerly known as indeterminatecolitis), or

• primary sclerosing cholangitis

• Have had or will need bowel resection or intestinal or intra-abdominal surgery

• Have evidence of toxic megacolon, intra-abdominal abscess, or stricture or stenosiswithin small bowel or colon that cannot be traversed by a colonoscope or that aresymptomatic

• Have any adenomatous polyp occurring in areas of the colon not involved by colitis,that has not been removed

Note: If such an adenomatous polyp has been completely removed and shows only low-grade dysplasia, this criterion would no longer apply

• Have a current or recent acute, active infection