A single liver-sparing myotropic AAV ameliorates muscular dystrophy in humanized mice by base editing

Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene, most of which are large exon deletions that result in loss of dystrophin protein. Adenine base editing (ABE) enables permanent gene correction by modifying splice sites to cause exon skipping and restoration of the DMD open reading frame. We previously demonstrated that adeno-associated virus 9-mediated (AAV9-mediated) delivery of adenine base editors allows efficient gene editing in mouse models of DMD. However, conventional AAV-based gene delivery approaches are complicated by their limited packaging capacity and high-dose-related toxicity. Here, we describe a single AAV vector encoding a compact adenine base editor, SlugABE8e, and a single-guide RNA, which enable efficient editing in a humanized DMD mouse model at a lower dose using the muscle-tropic MyoAAV4 capsid. Systemic MyoAAV4A delivery in juvenile DMD mice efficiently restored dystrophin expression in the heart and skeletal muscles. This molecular rescue was accompanied by reduced serum creatine kinase activity and diminished muscle pathology. A liver-detargeted MyoAAV4E-off capsid eliminated viral entry and editing in the liver. We also explored a high-fidelity base editor, SlugHF-ABE8e(V106W), which showed similar on-target and off-target editing to SlugABE8e. Together, these findings establish an all-in-one AAV strategy that efficiently mitigates DMD disease progression.