This study is looking at how well **etrasimod**, a drug, works for adults with a condition called **ulcerative colitis** (UC). UC is a disease that causes swelling in the large intestine. The study will watch patients who are already getting etrasimod as part of their regular care. It's important that patients have not taken this drug before. During the study, patients will answer questions about their UC symptoms using a device like a phone or computer. This will help doctors understand how the drug affects them. The study will last for 52 weeks, with an extra 28 days afterward to check safety. People who are part of this study must be 18 to 65 years old and have a doctor's note saying they have UC. However, people cannot join if they have other conditions like Crohn's disease or if they have had certain medicines before.

• The study lasts a total of 80 weeks, including follow-up.
• You need to complete health questionnaires online.
• Doctors will compare your UC activity before and during the use of etrasimod.