**Study Overview:** This clinical trial is testing a medicine called icotrokinra, a pill, for treating ulcerative colitis (UC). UC is a long-term illness where the large intestine gets sore and develops tiny open wounds. The study checks how well this medicine works and if it's safe for people 12 years and older who have moderate to severe UC. **Key Points:** - **Time Commitment:** The study requires regular visits for tests and check-ups. - **Eligibility:** Participants with UC not responding well to usual treatments are eligible. - **Risks:** People with serious issues like major surgeries or other gut problems may not join. **Details:** To join, you need a UC diagnosis from at least 12 weeks before the study starts. Participants should have a specific score from a test called the Mayo score, which measures UC severity. Pregnant women or those planning to become pregnant cannot participate. The study excludes those who have severe UC complications or recent major surgeries.