Givinostat enhances antisense oligonucleotide efficacy in the mdx52 model of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular disorder caused by mutations in the DMD gene, with deletions within the exon 45-55 hotspot being the most common. Despite advances in antisense oligonucleotide (ASO)-mediated exon skipping, therapeutic efficacy remains limited by suboptimal transcript availability and delivery barriers. We investigated whether histone deacetylase inhibitors (HDACis), particularly givinostat, can enhance the efficacy of an exon 51-targeting ASO in the clinically relevant mdx52 mouse model. For the first time, we identified a pronounced 5'-3' DMD transcript imbalance associated with exon 52 deletion, contrasting with the classical mdx model and potentially compromising ASO effectiveness. In human DMD myoblasts carrying an exon 52 deletion, givinostat significantly improved exon skipping and dystrophin restoration. In vivo, givinostat and ASO co-treatment resulted in a modest but significant increase in dystrophin levels compared to ASO alone (1.3-fold), along with reduced muscle fibrosis, improved fiber morphology, and better extracellular matrix organization. Notably, treated mice showed improved muscle function, as evidenced by a significant reduction in force loss after eccentric contractions, a clinically meaningful outcome. Although the precise molecular mechanisms underlying these effects remain to be fully elucidated, these findings support the therapeutic potential of combining givinostat with ASOs to enhance dystrophin restoration and muscle preservation in DMD.