An Open-label Long-term Follow-up Study of SAT-3247 for Participants With Duchenne Muscular Dystrophy Including Those Who Participated in SAT-3247-CL-101

Inclusion Criteria: * Previously participated in the SAT-3247-CL-101 parent clinical trials. * Continued status of stable glucocorticosteroid dose or no glucocorticosteroid dose from parent clinical trial. * Continued stable doses of prescription medicines (excluding glucocorticosteroids) and over-the-counter medicines and/or herbal supplements for supportive care from parent clinical trial. * Ability to understand the nature of the trial and any hazards of participating. * Ability to communicate satisfactorily with the investigator and physiotherapist and to participate in and comply with the requirements of the entire trial including scheduled visits, procedures, laboratory tests, questionnaires, wearable devices, and study restrictions. * Willingness to give written consent or assent (if not of cognitive capacity of consent in the jurisdiction where the study is being conducted) and parent/legal guardian willing to give written consent to participate (if participant is not of cognitive capacity to consent) after reading the information and consent form, and after having the opportunity to discuss the trial with the investigator or their delegate. * All participants, if sexually active, agree to follow the contraception requirements and sperm donation limitations of the trial as described in the protocol. Exclusion Criteria: * Presence of acute medical condition, chronic illness or history of chronic illness (other than DMD) sufficient to invalidate the participant's par…