Viltolarsen targets which exon in the DMD gene?

• A. Exon 53
• B. Exon 45
• C. Exon 51
• D. Exon 44

Answer: (A)

Exon skipping therapy uses a designed molecule to bind a specific stretch of the dystrophin pre-mRNA and cause that exact exon to be skipped during splicing. This can restore the reading frame if a mutation would otherwise disrupt it, producing a shorter but functional dystrophin protein.

Viltolarsen is crafted to bind to exon 53 of the DMD gene, causing exon 53 to be skipped in the mature mRNA. For patients whose mutations would disrupt the reading frame unless exon 53 is removed, skipping this exon can reframe the transcript and allow production of dystrophin.

So the targeted exon is exon 53. This approach is mutation-specific and explains why the therapy is used only for patients whose mutations are amenable to skipping that particular exon.