A Study to Evaluate the Pharmacokinetics, Safety and Efficacy of Afimkibart (RO7790121) in Children With Moderately to Severely Active Ulcerative Colitis

This study tests a new biologic medication called afimkibart (RO7790121) in children with moderately to severely active ulcerative colitis (UC) — a condition that causes chronic inflammation and sores in the large intestine — who have not responded well enough to standard treatments. **You may be eligible if...** - You are a child with a confirmed diagnosis of ulcerative colitis - You weigh at least 10 kg (about 22 lbs) - Your UC has not responded adequately to, or you could not tolerate, standard treatments including steroids, immunosuppressants, or biologic therapies **You may NOT be eligible if...** - You have Crohn's disease, indeterminate colitis, or infectious colitis - You have a colostomy or ileoanal pouch - You have active tuberculosis - You had major surgery within the past 6 weeks - You are suspected of having primary sclerosing cholangitis (a liver condition) Talk to your doctor to see if this trial is right for you.