Antisense oligonucleotides have been used for experimental gene silencing and recently as splice-switching oligonucleotides to modify splicing and induce exon skipping,13 particularly in myoblasts from patients with DMD in vitro,14, 15 and in mouse and dog models of DMD.16, 17, 18 One patient with DMD who had a deletion of exon 20 received an intravenous infusion of a splice-switching oligonucleotide with a phosphorothioate backbone, which induced skipping of exon 19 and restored the DMD open reading frame in lymphocytes but had no effect in skeletal muscle.19 This evidence concerns the gene DMD and Duchenne muscular dystrophy.