DMD and Duchenne muscular dystrophy: Restoration of dystrophin expression by exon skipping has been proven to be efficacious in vitro, in animal models and in DMD patients.11, 12, 13 Several classes of chemical modifications have been developed for AON-mediated exon skipping, among which are 2′O-methylribooligonucleoside-phosphorothioate (2′OMe), phosphorodiamidate morpholino oligomers (PMOs), and tricyclo-DNA (tc-DNA).