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

Inclusion Criteria10

• 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.