Study to Measure Filgotinib in the Blood of Children and Teenagers With Arthritis Taking Filgotinib (SCALESIA)

An Open-label, Multiple Dose, Multicenter Study to Evaluate the Pharmacokinetics, Safety, and Tolerability of Filgotinib in Children and Adolescents From 8 to Less Than 18 Years of Age With Juvenile Idiopathic Arthritis

A Study to evaluate the pharmacokinetics, safety, and tolerability in paediatric population for treating juvenile idiopathic arthritis (JIA).

Key Inclusion Criteria:

• Participant with a body mass index (BMI) within the 5th to 95th percentiles for the age and gender (based on World Health Organization BMI charts). Participant must have a minimum weight of 15 kg.

• Participant must meet the International League of Associations for Rheumatology classification for 1 of the following categories and have, according to the investigator's judgment, moderately to severely active disease that is not adequately controlled with his/her current therapy.

  • Rheumatoid factor (RF)-positive polyarthritis
  • RF-negative polyarthritis
  • Oligoarthritis
  • Psoriatic arthritis
  • Enthesis-related arthritis (ERA) Note: Historical Human leukocyte antigen B-27 (HLA-B27) results are considered appropriate for ERA diagnosis during screening.
  • Systemic JIA with active arthritis without active systemic features, or with active systemic features that are stable in the prior 6 months of time of enrollment

• Participant with intolerance or a history of inadequate response to at least one of the following medications for the treatment of JIA, administered for at least 12 weeks, based on current treatment guidelines: conventional synthetic disease-modifying antirheumatic drugs and biological disease-modifying antirheumatic drugs (including methotrexate) and non-steroidal anti-inflammatory drugs for ERA and psoriatic arthritis.

• Female participants of childbearing potential (i.e. who have passed menarche) must have a negative highly sensitive urine pregnancy test.

Key Exclusion Criteria:

• Participant with persistent oligoarthritis.
• Participant with undifferentiated arthritis.
• Participant with any other any other rheumatic, inflammatory, or immunologic disease (e.g. inflammatory bowel disease, hypogammaglobulinemia, systemic lupus erythematosus, or uncontrolled uveitis).
• Active infection that is clinically significant, as per judgment of the investigator.
• Participant 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, or atypical mycobacteria).

Note: Other protocol defined Inclusion/ Exclusion criteria may apply.