Systemic delivery of AAV5, AAV8, and AAV9 packaging a C5-12-microdystrophin-FLAG expression cassette in non-human...

Safely achieving therapeutic expression levels with adeno-associated virus (AAV) gene therapy is a significant challenge for treating the large muscle mass in humans. Non-human primates (NHPs) provide a more accurate assessment of the feasibility of achieving an effective and safe dose than rodents. Here, we compared a single systemic administration of AAV5, AAV8, or AAV9 in NHPs, each packaging the C5-12-microdystrophin-FLAG expression cassette. At 1 month post-dose, we compared tissue vector genomes, mRNA, and microdystrophin-FLAG protein levels by meso-scale discovery-enzyme-linked immunosorbent assay, liquid chromatography-mass spectrometry, and immunofluorescence. The C5-12 promoter was highly selective for heart and skeletal muscles, when compared to off-target tissues such as peripheral blood mononuclear cells, lung, liver, and kidney. AAV8 led to higher levels of microdystrophin-FLAG mRNA and protein in the cardiac ventricles and skeletal muscles when compared to AAV5 or AAV9. The AAV8-microdystrophin-FLAG led to ∼20% of wild-type NHP dystrophin protein expression levels and was located on the sarcolemma of ∼40% of skeletal muscles fibers and ∼15% of left ventricular cardiomyocytes. Hematology, serum chemistry, and pathology were unremarkable. Thus, a systemic dose of ∼1.18 × 10¹⁴ vector genomes/kg AAV8 is predicted to be safe and efficacious for treating Duchenne muscular dystrophy (DMD) but has significant room for improvement.