Safety, Tolerability, Pharmacokinetics, and Efficacy of Filgotinib in Children and Adolescents with Polyarticular-Course Juvenile Idiopathic Arthritis

The primary objective of this study is to evaluate the safety, tolerability, pharmacokinetics, and efficacy of filgotinib in pediatric and adolescent patients aged 8 to less than 18 years diagnosed with polyarticular-course juvenile idiopathic arthritis.

Secondary objectives include:

• Assessment of clinical response to achieve efficacy in the target population.
• Evaluation of the incidence of uveitis.
• Characterization of the pharmacokinetics of filgotinib and its primary metabolite, GS-829845.
• Comparison of the acceptability between the pediatric film-coated tablet formulation and the commercial film-coated tablet formulation.

This clinical trial includes a total of 8 participants diagnosed with polyarticular-course juvenile idiopathic arthritis. The study population consists of both male and female patients between the ages of 8 and 18 years. Inclusion requires that subjects meet the ILAR classification and exhibit moderately to severely active disease that is inadequately controlled by current therapeutic regimens. Eligible participants must have demonstrated a history of inadequate response or intolerance to at least one conventional synthetic disease modifying anti-rheumatic drug, such as methotrexate, or a biologic disease modifying anti-rheumatic drug administered for a minimum of 3 months. Additionally, subjects must be able to comply with the clinical protocol and provide appropriate consent or assent.

This multicenter, open-label study is designed to evaluate the safety, tolerability, pharmacokinetics, and efficacy of filgotinib in pediatric subjects aged 8 to less than 18 years diagnosed with polyarticular-course juvenile idiopathic arthritis. The research methodology aims to assess treatment-emergent adverse events and clinical responses such as the American College of Rheumatology response and changes in the Juvenile Arthritis Disease Activity Score. Participants undergo a screening process to ensure compliance with inclusion criteria, including moderate to severe disease activity and inadequate response to previous disease modifying anti-rheumatic drugs. The study involves monitoring pharmacokinetic parameters of filgotinib and its primary metabolite, alongside evaluating the acceptability of various oral formulations. Primary endpoints include the frequency and severity of adverse events through approximately Week 22 or for the duration of the study. The overall trial is estimated to occur between January 2026 and December 2027.

The investigational product GLPG0634 is administered as a film-coated mini-tablet. The dosage consists of 100 mg delivered via the oral route.

The experimental treatment Jyseleca is provided in two different pharmaceutical forms. One version consists of film-coated tablets at a dosage of 100 mg, while the other consists of film-coated tablets at a dosage of 200 mg. Both formulations are administered through oral use. The active substance in these products is filgotinib.

The assessment of efficacy in subjects with polyarticular-course juvenile idiopathic arthritis involves several secondary endpoints. The American College of Rheumatology (ACR) 30 response and the rate of inactive disease will be evaluated at Week 12 and Week 18. Clinical activity will be measured by evaluating the change from baseline in the Juvenile Arthritis Disease Activity Score (JADAS)-27, specifically incorporating erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) at the same timepoints. Additionally, the Pediatric Oral Medicine Acceptability Questionnaire for Patients (POMAQ-P) will be utilized to assess the acceptability of the pediatric formulation and the adult film-coated tablet formulation.