Activation of endogenous full-length utrophin by MyoAAV-UA as a therapeutic approach for Duchenne muscular dystrophy

Activation of endogenous full-length utrophin, a dystrophin homolog, presents an attractive therapeutic strategy for Duchenne muscular dystrophy (DMD), regardless of mutation types and loci. However, current dCas9-based activators are too large for efficient adeno-associated virus delivery, and the feasibility and durability of such treatments remain unclear. Here, we develop a muscle-targeted utrophin activation system using the compact dCasMINI-VPR system, termed MyoAAV-UA. Systemic administration of MyoAAV-UA in male mdx mice leads to substantial upregulation of utrophin at the sarcolemma, resulting in significant improvements in skeletal muscle function and a slowing of heart function deterioration. These benefits remain observable at six months post-treatment. In male nonhuman primates, systemic administration of MyoAAV-UA increases utrophin expression by twofold in skeletal muscle, with no significant side effects observed. Furthermore, MyoAAV-UA upregulates utrophin and utrophin-glycoprotein complexes in induced pluripotent stem cell-derived myotubes from DMD patients. In conclusion, these findings demonstrate the potential of MyoAAV-UA as a therapeutic approach for DMD.