A new approach to correcting mutations in the DMD gene upstream of exon 20 was achieved by inserting into the native intron 19, which holds the sequence of exons 1-19, along with a new promoter. This method builds on previous insertion approaches, bypassing any upstream truncating mutations and allowing full-length dystrophin expression when spliced. The insertion is made through twin prime editing to avoid any double-stranded break of the genome, and can be translated into a therapy for patients.