An Open-label Phase II Trial to Evaluate the Clinical Efficacy, Safety and Tolerability of MAS825 in Pediatric and Adult Participants With Still's Disease

This is a multicenter, open-label, single-arm study to assess clinical efficacy, safety and tolerability of MAS825 in participants (both pediatric and adult) with Still's disease who have had inadequate response to IL-1 and/or IL-6 or other available therapies. Participants with associated lung disease and/or macrophage activation syndrome may also be included. This study has three periods (Screening, Treatment Period 1, and Treatment Period 2) and a total duration of approximately 16 months.