A Study Evaluating the Effects of Filgotinib in Children and Teenagers With Ulcerative Colitis

Who May Qualify: - Subject must have a minimum body weight (BW) of 15 kg. - Subject: - has documented diagnosis of UC with a minimum duration of 3 months, - has mMCS of 5 to 9, and an MCS endoscopic score \>=2, rectal bleeding \>=1, and stool frequency \>=1, - has had an inadequate response, loss of response, intolerance, or has medical contraindications to corticosteroids, immunosuppressants, and/or biologic therapy. This includes subjects who depend on corticosteroids to control their symptoms and who experience worsening of their disease when attempting to wean off corticosteroids. Who Should NOT Join This Trial: - Subject has a diagnosis of inflammatory bowel disease -unclassified or indeterminate colitis, isolated proctitis, or toxic megacolon. - Subject has an active infection. - Subject with a history of complicated herpes zoster infection (with multi-dermatomal, disseminated, ophthalmic, or central nervous system involvement). - Currently on any therapy for chronic infection (such as pneumocystis, cytomegalovirus, herpes simplex, herpes zoster, or atypical mycobacteria). - Subject has a history of colectomy or extensive small bowel resection. - Subject with psychological or cognitive difficulties that might interfere with study participation. - Subject has any previous exposure to a Janus kinase inhibitor or medication with a similar mode of action (e.g. tofacitinib, baricitinib, upadacitinib). - Female subject is pregnant or breast feeding or intending to become pregnant or breastfeed during the study. Always talk to your doctor about whether this trial is right for you.