This study is testing a new medicine called duvakitug to see if it helps people with Ulcerative Colitis (UC), a type of bowel disease that causes inflammation and sores in the colon. The study will last up to 35 weeks and includes several smaller parts where people will get the medicine for up to 12 weeks. The study will compare duvakitug to a placebo, which is a treatment with no active medicine, to see how effective and safe it is.

To join, you need to be between 16 and 80 years old and have had UC for at least 3 months. If you've tried other treatments that didn't work, you might be eligible. They will not accept people with Crohn's Disease, certain bowel surgeries, or if you've taken certain other medications.

• The study has up to 15 visits, depending on your response to the treatment.
• You'll be in the study for about 35 weeks, including follow-ups.
• Participants will be randomly assigned to receive either the study drug or a placebo.