Investigation of the pentamidine efficacy against myotonic dystrophy type 1 exploiting polymeric- and lipid-based nanoparticles

Myotonic dystrophy type 1 (DM1) is a genetic disorder caused by a mutation in the DMPK gene, in which an expanded CTG trinucleotide is transcribed into abnormal mRNA that accumulates in nuclear foci. These foci sequester crucial splicing factors, causing a strong mis-regulation of downstream target genes. Consequently, DM1 causes dysfunctions of multiple organs, including skeletal muscle. Currently, no cure exists for DM1, although significant efforts are underway to develop novel therapeutic strategies. Pentamidine (PTM), a drug currently used as an antiparasitic agent, has been shown to reduce nuclear foci formation, and restore normal splicing patterns; however, its clinical translation via systemic administration (e.g., intravenous) for widespread muscle targeting is severely limited by a narrow therapeutic window and organ toxicities. Nanocarriers (NCs) may improve drug efficacy by enabling targeted delivery while reducing side effects and the required therapeutic dose. Although active surface functionalization would be required for organ-specific targeting in vivo, non-functionalized platforms provide a primary baseline for evaluating fundamental uptake and efficacy. In this study, we explored in vitro the potential of different formulations of poly(lactic-co-glycolic) acid-based nanoparticles, liposomes, and nanohydrogels as safe and efficient NCs for PTM delivery to skeletal muscle (C2C12) cells. The most suitable concentration for each PTM-loaded formulation was assessed by a cell viability assay, while NC uptake and potential cell damage were evaluated using transmission electron microscopy. Finally, the therapeutic efficacy of PTM-loaded NCs was tested in cells transfected with human (CTG)n expansion to express nuclear mRNA foci. Three NC formulations significantly reduced nuclear foci, while improving cell viability and prolonging the therapeutic effect compared with PTM administered as free molecule. Although obtained in vitro, these results open promising perspectives for NCs as therapeutic tools for DM1.