Evaluate Efficacy, Safety and Tolerability, PK and PD of Emapalumab in Children and Adults With MAS in Still's or SLE

Inclusion criteria

• ✓. Informed consent provided by the subject or by the subject s' legally authorized representative(s) with the assent of subjects who are legally capable of providing it, as required by local law.
• ✓. Male and female subjects aged between 6 months and 80 years of age at the time of diagnosis of MAS.
• ✓. MAS defined as per the criteria defined below for each cohort and requiring treatment with GCs.
• ✓. Informed consent provided by the subject or by the subject's legally authorized representative(s) with the assent of subjects who are legally capable of providing it, as as required by local law.
• ✓. Male and female subjects aged between 6 months and 80 years of age at the time of diagnosis of active MAS.
• ✓. Subjects who have shown an inadequate response to high dose intravenous (i.v.) GCs administered for at least 3 days according to local standard clinical practice, including but not limited to pulses of 30 mg/kg PDN on 3 consecutive days. High i.v. GCs dose is recommended not to be lower than 2 mg/kg/ day PDN equivalent (or at least 60 mg/day in pediatric subjects of 30 kg or more, and at least 1g/day in adult MAS subjects). In case of rapid worsening of the subject's condition and/or laboratory parameters, as per Investigator judgment, inclusion may occur within less than 3 days from starting high dose GCs.
• ✓. Diagnosis of active MAS confirmed by the treating rheumatologist, having ascertained the followings:
• ✓. Female subjects of child-bearing potential willing to use highly effective methods of contraception from study drug initiation to 6 months after the last dose of study drug.

Exclusion criteria