This clinical trial is focused on studying Duchenne Muscular Dystrophy (DMD), a genetic disorder characterized by progressive muscle weakness and degeneration. The study will evaluate a treatment called Delandistrogene Moxeparvovec, also known by its code name SRP-9001. This treatment is a type of gene therapy, which involves introducing new genetic material into the body to help treat the disease. The trial will also use a placebo, which is a substance with no active therapeutic effect, to compare the results.

The purpose of the study is to assess the safety and effectiveness of Delandistrogene Moxeparvovec in both non-ambulatory (those who cannot walk) and ambulatory (those who can walk) participants with Duchenne Muscular Dystrophy. Participants will receive the treatment through an intravenous infusion, which means the solution is delivered directly into the bloodstream. The study will monitor changes in muscle function and other health indicators over a period of time, with key assessments occurring at 72 weeks after the start of the trial.

Throughout the study, researchers will track various health outcomes, including muscle strength and respiratory function, to determine the impact of the treatment. The trial will also measure the amount of dystrophin, a protein that is typically lacking in individuals with Duchenne Muscular Dystrophy, produced by the body after receiving the gene therapy. Participants will be closely monitored for any side effects or adverse reactions to ensure their safety during the trial.