This study is looking at how well a new treatment called RO7790121 works for people with *ulcerative colitis (UC)*, a condition causing inflammation in the colon, and how safe it is. The study is **Phase III**, which means it's in the final testing stage before possibly becoming available to the public. It is *double-blind* and *placebo-controlled*, meaning neither you nor the researchers will know if you're getting the real treatment or a placebo (a fake treatment) until the study ends.

To join, you must be diagnosed with moderate to severe UC, weigh at least 40 kilograms, and have tried other UC treatments without success. You can't join if you have specific complications or other conditions, like Crohn's disease or active infections.

• **Study Length**: Not specified, but usually lasts several months.
• **Visits Required**: You will need to visit the study center for check-ups and treatment.
• **Risks**: Potential side effects like those from other UC treatments, and risks related to not knowing if you are receiving the real treatment.