SORT LNPs encapsulating Cas9 mRNA achieve efficient editing in skeletal muscle in a dystrophic mouse model

Limb girdle muscular dystrophy (LGMD) is the fourth most common type of muscular dystrophy. Gene editing holds promise for treating neuromuscular disorders such as LGMD, but clinical translation remains challenging due to lack of complementary delivery tools for skeletal muscle. Lipid nanoparticles (LNPs) offer a promising platform for transient delivery of gene-editing reagents as mRNA or ribonucleoprotein complexes (RNPs) to skeletal muscle, but editing efficiencies remain modest. While lipid compositions have been optimized to improve delivery to muscle, the impact of cargo type on editing efficiency, biodistribution, and immune response has not been evaluated. Here, we demonstrate that selective organ targeting (SORT) LNPs encapsulating optimized Cas9 cargo facilitate efficient, local delivery to skeletal muscle. Using an LGMDR7 mouse model harboring a mutation in TCAP as a proof-of-concept target, we show that LNP cargo type impacts LNP size, delivery to neighboring muscle groups, and editing efficiency. RNP and mRNA LNPs also provoked distinct innate and adaptive immune responses upon repeated dosing. The optimized SORT LNP platform resulted in 40% restoration of Telethonin expression in treated muscle. Overall, these findings offer valuable insights for the continued development of LNP-based gene-editing reagents to facilitate disease-modifying interventions for neuromuscular diseases.