**Study on Icotrokinra for Ulcerative Colitis** This study tests a new medicine called icotrokinra to see if it helps people with ulcerative colitis (UC). UC is a disease where the large intestine gets very sore and has tiny open sores. The study is for adults and teenagers with UC that is moderately to severely active. They want to know if the medicine works well and is safe to use. Eligibility means who can join the study. You can join if you have had UC for at least 12 weeks and your UC is active. Teenagers need to weigh at least 40 kilograms (about 88 pounds). Girls must have a negative pregnancy test. You should not have had certain surgeries or other problems with your UC. **Key Points:** - The study will check how well icotrokinra works and its safety for UC patients. - Participants who join must have had UC for at least 12 weeks and cannot have certain complications or surgeries. - Teenagers must weigh at least 40 kilograms, and all girls must pass a pregnancy test before starting. **Note:** Participants may need to stop other UC medications during the study.