A Study to Evaluate Efficacy and Safety of MK-8690 in Participants With Moderately to Severely Active Ulcerative Colitis (MK-8690-002)

The main inclusion criteria include but are not limited to the following:

* Has had ulcerative colitis (UC) (from onset of symptoms) for at least 3 months before Randomization
* Has moderately to severely active UC
* Has a weight ≥40 kg
* Satisfies at least 1 of the criteria: Has had an inadequate response or loss of response to 1 or more protocol-specified treatments; protocol specified corticosteroid dependence; has been intolerant to 1 or more protocol-specified UC treatments
* Is on treatment with any protocol-specified drugs during the study and meets drug stabilization requirements, as applicable

The main exclusion criteria include but are not limited to the following:

* Has a diagnosis of Crohn's Disease (CD) or indeterminate colitis (inflammatory bowel disease (IBD)-undefined) or other types of colitis or enteritis that may confound efficacy assessment
* Has a current diagnosis of fulminant colitis and/or toxic megacolon
* Has UC limited to the rectum
* Has a current or impending need for colostomy or ileostomy
* Has had a total proctocolectomy or partial colectomy
* Has UC exacerbation requiring hospitalization within 2 weeks before Screening
* Has any active infection as specified in the protocol
* Is known to be infected with hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV)
* Has evidence of active tuberculosis (TB) or meets TB exclusionary parameters
* Has a history of cancer (except fully treated nonmelanoma skin cell cancers or cervical carcinoma in situ after complete surgical removal) and is disease free for \<5 years before Randomization or has a history of colorectal cancer at any time
* Has prior or current evidence of definite colonic dysplasia except for low-grade dysplasia that has been completely removed
* Has had major surgery within 3 months before Screening or has a major surgery (ie, surgical procedure requiring general anesthesia) planned during the study
* Has received protocol-specified prohibited medications