(BUSINESS WIRE)--GlaxoSmithKline (GSK) and Prosensa today announced that the first patient has commenced treatment in the Phase III clinical study investigating GSK2402968, in ambulant boys with Duchenne Muscular Dystrophy (DMD), who have a dystrophin gene mutation amenable to an exon 51 skip (up to 13% of boys with DMD). Commencement of this study confirms previously announced plans to progress this asset into Phase III.