A Study to Evaluate Efficacy and Safety of Tulisokibart (MK-7240) in Participants With Moderately to Severely Active Ulcerative Colitis (MK-7240-001)

Prior treatment

• Has received fecal microbial transplantation within 4 weeks before randomization
• Has had UC exacerbation requiring hospitalization within 2 weeks before screening
• Has prior or current evidence of definite colonic dysplasia except for low-grade dysplasia that has been completely removed
• Has had cytomegalovirus infection that resolved less than 4 weeks before screening
• Has a history of drug or alcohol abuse within 6 months prior to screening
• Has had major surgery within 3 months before screening or has a major surgery planned during the study
• Is currently receiving or is planning to receive total parenteral nutrition at any time during study treatment
• Has received UC-related antibiotics and has not been on stable doses for at least 14 days before randomization or has discontinued these medications within 14 days of randomization
• Requires treatment with a therapy that does not adhere to the protocol-specified guidance parameters
• Has received protocol-specified prohibited medications
• Has had prior exposure to tulisokibart or another anti-tumor necrosis factor-like cytokine 1A (TL1A) antibody

Other illness

• 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 any active or serious infections without resolution after adequate treatment
• Has a history of cancer (except fully treated non-melanoma skin cell cancers or cervical carcinoma in situ after complete surgical removal) within the last 5 years
• 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), latent TB not successfully treated (per local guidelines), or inadequately treated TB (for participants with history of TB)
• Has confirmed or suspected COVID-19

Other

• Has a current diagnosis of fulminant colitis and/or toxic megacolon
• Has UC limited to the rectum (i.e, must have evidence of UC extending beyond the rectosigmoid junction, which is \~10 cm from the anal margin)
• Has a current or impending need for colostomy or ileostomy
• Has had a total proctocolectomy or partial colectomy
• Has a transplanted organ which requires continued immunosuppression

• Has had ulcerative colitis (UC) (from onset of symptoms) for at least 3 months before randomization
• Has moderately to severely active UC
• Weight ≥40 kg
• Satisfies at least 1 of the following criteria:
  • Has had an inadequate response or loss of response to 1 or more protocol-specified UC 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
• Adolescent participants ≥16 and \<18 years of age can participate if approved by the country or regulatory/health authority
• A participant assigned female sex at birth is eligible to participate if not pregnant or breastfeeding and Is not a participant of childbearing potential (POCBP); or is a POCBP and uses an acceptable contraceptive method, or is abstinent from penile-vaginal intercourse as their preferred and usual lifestyle (abstinent on a long-term and persistent basis), has a negative highly sensitive pregnancy test (urine or serum) as required by local regulations within 24 hours (for a urine test) or 72 hours (for a serum test) before the first dose of study intervention, medical history, menstrual history, and recent sexual activity has been reviewed by the investigator to decrease the risk for inclusion of a POCBP with an early undetected pregnancy