- Duchenne muscular dystrophy (DMD) is a disease in which the muscles are unable to make the protein dystrophin. Without this protein, the muscles become gradually weaker. A new medicine called GSK2402968 is being tested to see if it can help prevent or slow down this loss of muscle strength. In this study, boys with DMD and healthy volunteers will have different types of imaging studies to see which ones provide the best images of the muscles. This information will help researchers use these imaging techniques to test the safety and effectiveness of GSK2402968 and other agents.