A Repeated Dose-finding Study of Sarilumab in Children and Adolescents With Systemic Juvenile Idiopathic Arthritis (SKYPS)

Inclusion criteria : * Male and female patients aged ≥1 and ≤17 years (or country specified age requirement, ≥6 to ≤17 years for Russia) at the time of the screening visit. * Diagnosis of systemic JIA subtype according to the International Associations against Rheumatism (ILAR) 2001 Juvenile Idiopathic Arthritis (JIA) Classification Criteria OR According to 2024 EULAR/PReS recommendation at Screening. * Patient with an inadequate response to current treatment and considered as a candidate for a biologic disease modifying anti rheumatic drug (DMARD) as per investigator's judgment. Exclusion criteria: * Body weight \<10 kg or \>60 kg for patients enrolled in the ascending dose cohorts, then body weight \<10 kg for patients subsequently enrolled at the selected dose. * Uncontrolled severe systemic symptoms and/or Macrophage Activation Syndrome (MAS) within 6 months prior to screening. * History of or ongoing interstitial lung disease, pulmonary hypertension, pulmonary alveolar proteinosis. * If nonsteroidal anti-inflammatory drugs (NSAIDs) (including cyclo oxygenase-2 inhibitors \[COX-2\]) taken, dose stable for less than 2 weeks prior to the baseline visit and/or dosing prescribed outside of approved label. * If non-biologic DMARD taken, dose stable for less than 6 weeks prior to the baseline visit or at a dose exceeding the recommended dose as per local labeling. * If oral glucocorticoid taken, dose exceeding equivalent prednisone dose 1 mg/kg/day (or 60 mg/day) within 3 da…