M12 is a novel 12-mer peptide showing preferential binding to skeletal muscle compared to the liver. M12 peptide preferentially binds to skeletal muscle after systemic administration in adult mdx mice. When M12 was conjugated to PMO(phosphorodiamidate morpholino), the M12–PMO conjugate could effectively induce exon skipping and dystrophin restoration in body-wide skeletal muscles with the exception of heart after systemic administration in mdx mice. M12-PMO oligomer can be an alternative option to current AOs(Antisense oligonucleotide).