The aim of this study is to evaluate the efficacy, safety, tolerability, and pharmacokinetics (PK) of filgotinib as a treatment for UC in children and adolescents aged from 8 to less than 18 years.

Approximately 80 subjects from 8 to <18 years of age with moderately to severely active UC, including a minimum of 8 subjects from 8 to <12 years of age, will be enrolled in this study.

During the study, eligible subjects will take the investigational product (IP) on-site at Week 4, Week 10, and Week 22 (in the morning; with or without food). On all other days, subjects will take IP at home (in the morning; with or without food).

Subjects who do not achieve mMCS remission and/or MCS response at Week 10 will continue with induction treatment until Week 22. Subjects who do not achieve PUCAI remission at Week 22 will be permanently discontinued from the study.

Subjects will all receive a filgotinib dose targeting the same systemic exposure as that observed in adults with UC treated with 200 mg q.d.

Inclusion Criteria:

• 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.

Exclusion Criteria:

• 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.