This study is testing a new medicine called tulisokibart for people with ulcerative colitis (UC), a condition that causes inflammation and sores in the colon. The goal is to see if tulisokibart helps more than a placebo (a pill with no medicine) in getting people to feel better by 12 and 52 weeks, using a tool called the Modified Mayo Score, which measures symptoms like pain and bleeding.

Participants need to have UC for at least 3 months and have tried other treatments that didn't work well. They must weigh at least 40 kg (about 88 pounds) and cannot be pregnant or breastfeeding if they are capable of having children. The study has two parts, with the first including an initial and maintenance treatment phase, while the second includes only the initial phase.

• Study lasts up to 52 weeks with regular check-ups.
• Participants must meet certain health criteria, like not having other types of bowel disease.
• Participants will not receive compensation, but will help advance UC treatment research.