This clinical trial is focused on studying a condition called Type 1 facioscapulohumeral muscular dystrophy (FSHD1). FSHD1 is a genetic disorder that causes muscle weakness, primarily affecting the face, shoulders, and upper arms. The study will explore the effects of a treatment called satralizumab, which is a type of medication known as a monoclonal antibody. Monoclonal antibodies are proteins designed to target specific substances in the body. In this study, satralizumab will be compared to a placebo, which looks like the treatment but does not contain the active ingredient.
The purpose of the study is to evaluate the effectiveness and safety of satralizumab in patients with FSHD1. Participants will receive either satralizumab or a placebo through an injection under the skin. The study will last for a total of 96 weeks, with the first 48 weeks being a double-blind period, meaning neither the participants nor the researchers will know who is receiving the actual treatment or the placebo. After this period, there will be an open-label phase where all participants may receive satralizumab. Throughout the study, various assessments will be conducted to monitor changes in muscle strength, physical abilities, and overall health.
Participants will undergo regular check-ups, including MRI scans to examine muscle condition, and will be asked to maintain their usual level of physical activity. The study aims to provide valuable insights into how satralizumab can help manage symptoms of FSHD1 and improve the quality of life for those affected by this condition. The safety of the treatment will also be closely monitored by tracking any side effects or adverse reactions experienced by participants.



France