Treating Myotonic Dystrophy with artificial RNA endonucleases to specifically degrade toxic RNA expansions

ABSTRACT Myotonic dystrophy type 1 (DM1), the most common autosomal dominant muscular disorder, is driven by expanded CUG repeats in the 3′ UTR of DMPK gene, which sequester RNA-binding proteins and cause aberrant alternative splicing. Despite extensive study, no effective treatment exists, and current care remains limited to symptomatic management. Using a customized dual-color reporter carrying RNA repeats in different lengths, we engineered a new class of programmable artificial enzymes (artificial RNA cleavers, or ARCs) that preferentially degrade the pathogenic repeats both in cells and in a mouse model. We further examined the in vivo efficacy of ARCs by systematically delivering ARCs into the DM1 mouse model with muscle-specific adeno-associated viruses, and validated that ARCs can rescue the muscular pathology and movement ability. The treatment by ARCs showed sustained efficacy, low immunogenicity, and minimal off-target effects in animal model, which are key concerns in clinical translation of gene therapies. Collectively, these findings establish ARCs as a potent and precise RNA-targeting platform with strong clinical potential for the treatment of DM1 and other repeat expansion disorders. Competing Interest Statement M.M., Z.W. and T.W. are inventors on a patent application related to the work about the ARC systems (No. WO2025/016408). H.H. and X.X. are inventors on a Chinese patent application related to the work about the iAAV9.6 vector (No. CN202510458749.9). The other authors declare no other competing interests.