Lipid nanoparticle delivery of antisense gapmers attenuates pathology in a mouse model of facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a progressive muscle-wasting disease caused by aberrant activation of the DUX4 gene in skeletal muscle. Antisense oligonucleotides (ASOs) targeting DUX4 have shown therapeutic potential, but challenges related to systemic delivery and efficacy limit their clinical utility. In this study, we explored lipid nanoparticle (LNP)-mediated delivery of optimized locked nucleic acid (LNA) and 2'-O-methoxyethyl (MOE) gapmers to enhance their therapeutic potential. In FSHD patient-derived muscle cells, gapmers reduced DUX4 expression and improved myogenic differentiation indices relative to non-treated controls. In vivo studies demonstrated that LNP encapsulation increased gapmer bioavailability in skeletal muscle tissues compared to bare gapmers while maintaining a favorable safety profile. A single systemic injection in iDUX4pA mice moderately reduced DUX4 levels without significant functional improvement. However, repeated weekly injections resulted in up to ∼60% knockdown of DUX4 in skeletal muscles, repression of its downstream targets, improved grip strength and treadmill performance, and amelioration of muscle pathology. This study indicates that LNP-mediated gapmer delivery could be a candidate strategy to improve skeletal muscle biodistribution in iDUX4pA mice. This work provides preliminary proof of concept for further preclinical optimization and additional safety and efficacy studies.