This clinical trial is focused on studying ulcerative colitis, a condition that causes inflammation and sores in the colon and rectum. The study is specifically looking at adolescents aged 12 to 17 who have moderately to severely active ulcerative colitis. The treatment being tested is a medication called Etrasimod, which is taken as a capsule. Etrasimod is being evaluated for its ability to help achieve clinical remission, which means reducing or eliminating the symptoms of ulcerative colitis.

The purpose of the study is to assess how effective Etrasimod is in helping adolescents with ulcerative colitis achieve clinical remission after 52 weeks of treatment. Participants in the study will take Etrasimod daily, and their progress will be monitored over the course of the study. The study will also look at how the body processes the medication and its safety in this age group. Some participants may receive a placebo, which is a capsule that looks like the medication but does not contain the active ingredient.

Throughout the study, researchers will check for improvements in symptoms and any side effects. They will also conduct tests to see how the medication is working in the body. The study aims to provide valuable information on the potential benefits and safety of Etrasimod for treating ulcerative colitis in adolescents. The study is expected to continue until 2028, allowing researchers to gather comprehensive data on the long-term effects of the treatment.