Inclusion Criteria:
* Diagnosis of UC with disease duration of at least 12 weeks prior to randomization
* Evidence of active UC at Screening, defined by all of the following:
1. MMS of 5 to 8, inclusive;
2. ES ≥ 2;
3. RBS of ≥ 1; and
4. Evidence of active UC extending ≥15 cm from the anal verge via colonoscopy (confirmed by central read)
* UCEIS score ≥ 4 with erosion/ulcer sub-score of ≥1 (confirmed by central read)
* An inadequate response to, loss of response to, or intolerance to at least 1 of the following conventional therapies as defined below:
1. Oral 5-ASA compounds
2. Glucocorticoids (topical or systemic)
3. Thiopurines
* If receiving oral 5-aminosalicylates (5-ASAs) or oral corticosteroids (≤20 mg prednisolone equivalent) for treatment of their UC, they must be on a stable dose for at least 28 days prior to randomization
* Previous exposure to a single biologic agent, JAK inhibitor, or S1P inhibitor is allowed (not required) if it was discontinued for reasons other than primary no response. Discontinuation must have been more than 8 weeks or 5 half-lives (whichever is longer) prior to first dose of study treatment.
Exclusion Criteria:
* Severe extensive colitis as evidenced by:
1. Likeliness to require hospitalization for medical care or surgical intervention of any kind for UC (e.g., colectomy) within 12 weeks after randomization
2. Current evidence of fulminant colitis, toxic megacolon, or recent history (within 6 months prior to screening) of toxic megacolon, or bowel perforation
* Has severe UC during as defined by ≥6 bloody stools per day AND at least 1 of the following during Screening:
1. Pulse \>90 bpm
2. Oral temperature of \>37.8 °C
3. Hemoglobin \<10.5 g/dL
4. CRP of \>30 mg/L
5. Erythrocyte sedimentation rate \>30 mm/h
* Diagnosis of Crohn's disease (CD) or indeterminate colitis, microscopic colitis, ischemic colitis, radiation colitis, acute diverticulitis, or the presence or history of a fistula consistent with CD based on medical history
* History of or current evidence of colonic dysplasia; or recent history (within 2 years prior to randomization). Note: If adenomatous polyps present, must be completely removed per routine practice prior to the study participant's first dose of investigational product.
* History of colectomy (total or subtotal), ileoanal pouch, Kock pouch, or ileostomy; or is planning to undergo bowel surgery during the course of the study.
* History of spontaneous gastrointestinal (GI) perforation (other than appendicitis or mechanical injury), or at significantly increased risk of GI perforation based on the Investigator's judgment
