Ataluren: only helpful if nonsense mutation is present in the DMD gene; the drug ensures that instead of a stop codon (causes abortion of translation (translation of mRNA into protein) and thus shortened protein), the amino acid essential for the protein is incorporated, resulting in the functional dystrophin protein. The earlier the drug is supplemented, the longer the chances of retaining walking ability and muscle function.
Eteplirsen: Helps only with deletion (loss of a middle chromosomal piece) in exon 50 (gene segment that is not cut out during splicing (pre-RNA processing) and thus essential for translation); this deletion is present in 15% of sufferers. The drug is a single-stranded nucleic acid complementary to exon 51 of the pre-mRNA. Thus, it binds to the said exon. Because of the binding, the exon is removed during splicing (an important step in the processing that creates functional RNA). The protein may now be shortened, but from the location of exon 51 the reading frame is altered in such a way that from there on the correct amino acid sequence of the protein is encoded. The dystrophin is thus partially functional. Only approved in the USA!
