Duchenne muscular dystrophy (DMD) is one of the most common and lethal genetic 
disorders, with 20,000 children per year born with DMD globally. DMD is caused 
by mutations in the dystrophin (DMD) gene. Antisense-mediated exon skipping 
therapy is a promising therapeutic approach that uses short DNA-like molecules 
called antisense oligonucleotides (AOs) to skip over/splice out the mutated part 
of the gene to produce a shortened but functional dystrophin protein. One major 
challenge has been its limited applicability. Multiple exon skipping has 
recently emerged as a potential solution. Indeed, many DMD patients need exon 
skipping of multiple exons in order to restore the reading frame, depending on 
how many base pairs the mutated exon(s) and adjacent exons have. Theoretically, 
multiple exon skipping could be used to treat approximately 90%, 80%, and 98% of 
DMD patients with deletion, duplication, and nonsense mutations, respectively. 
In addition, multiple exon skipping could be used to select deletions that 
optimize the functionality of the truncated dystrophin protein. The proof of 
concept of systemic multiple exon skipping using a cocktail of AOs has been 
demonstrated in dystrophic dog and mouse models. Remaining challenges include 
the insufficient efficacy of systemic treatment, especially for therapies that 
target the heart, and limited long-term safety data. Here we review recent 
preclinical developments in AO-mediated multiple exon skipping and discuss the 
remaining challenges.