A Study to Investigate the Safety and Efficacy of Emapalumab, an Anti-IFN-gamma mAb in Patients With Systemic Juvenile Idiopathic Arthritis (sJIA) or Adult-onset Still's Disease (AOSD) Developing Macrophage Activation Syndrome/Secondary HLH (MAS/sHLH)

A Pilot, Open-label, Single Arm, Multicenter Study to Evaluate Safety, Tolerability, Pharmacokinetics and Efficacy of Intravenous Administrations of Emapalumab, an Anti-interferon Gamma (Anti-IFNγ) Monoclonal Antibody, in Patients With Systemic Juvenile Idiopathic Arthritis (sJIA) or Adult-onset Still's Disease (AOSD) Developing Macrophage Activation Syndrome/Secondary HLH (MAS/sHLH)