This study is testing tofacitinib, a medication, in children 2 to 17 years old with moderate to severe ulcerative colitis (UC). UC is a disease that causes inflammation in the colon. The study wants to see if tofacitinib helps improve UC symptoms. In the United States and Europe, only patients who did not do well with previous treatments can join. All participants will start with a low dose of tofacitinib and may increase it if needed. The study will last up to about 180 weeks (over 3 years) and includes different phases: initial treatment, maintenance, and an extension period. Participants will visit the study site regularly and be monitored for any side effects.
- Study duration can be up to 180 weeks with several phases.
- Participants will start with a low dose of tofacitinib.
- Regular visits for monitoring and follow-ups are required.