Ulcerative colitis (UC) is a disease that makes the large intestine (colon) and rectum inflamed, causing bleeding. This study explores how Risankizumab, a medicine approved in many countries, works in children with UC. The aim is to understand how safe and effective it is for kids with moderate to severe UC. The study will watch for side effects and changes in symptoms.

There are three groups based on age, from 2 to less than 18 years. In the first part, participants receive Risankizumab through an IV (intravenous) for 12 weeks. In the second part, Risankizumab is given under the skin (subcutaneously) for 52 weeks. The final part extends over 208 weeks, continuing the skin injections. About 120 children will join this study in around 80 places worldwide.

Participants will have regular hospital or clinic visits for check-ups, blood tests, and questionnaires. This study might be more demanding than regular care.

• The study lasts for several years and involves regular clinic visits.
• Risankizumab is administered in different ways across various phases.
• Participants will be monitored closely for side effects and UC symptoms.