This is a phase I safety and tolerability study. Three DMD subjects will receive bilateral injections into the EDB muscle, with one EDB receiving the GALGT2 vector (rAAVrh74.MCK.GALGT2) and the other side receiving saline alone (assigned in a randomized fashion). Three subjects will receive a single gene transfer dose of 1E12 vector genomes, and patients and investigators will be blinded as to which muscle is injected with vector. Muscle biopsies will be performed at three months (12 weeks) in two subjects and at 1.5 months (6 weeks) in one subject and evaluated blindly for the expression of the GALGT2 transgene.