This clinical trial is focused on studying the effects of a medication called Upadacitinib in children and teenagers with Ulcerative Colitis. Ulcerative Colitis is a condition that causes inflammation and sores in the lining of the large intestine. The study aims to evaluate how well the medication works, its safety, and how it behaves in the body. Upadacitinib is a type of medication known as a Janus kinase (Jak) inhibitor, which helps to reduce inflammation by blocking certain signals in the body.

The trial involves several stages. Initially, all participants will receive Upadacitinib in an open-label phase, meaning everyone knows they are receiving the medication. After this, participants will be randomly assigned to either continue with Upadacitinib or receive a placebo in a double-blind phase, where neither the participants nor the researchers know who is receiving which treatment. This helps to ensure the results are unbiased. The study will also include a long-term extension phase where participants may continue to receive Upadacitinib openly.

The goal is to see if Upadacitinib can help achieve remission, which means the symptoms of Ulcerative Colitis are reduced or disappear. The study will look at how many participants achieve remission after 8 weeks and again after 52 weeks. Participants will be monitored throughout the study to assess the medication’s effectiveness and any side effects. This trial is important for understanding how Upadacitinib can be used to treat Ulcerative Colitis in young patients who have not responded well to other treatments like corticosteroids, immunosuppressants, or biologic therapies.