Toxicology Study of Intra-Cisterna Magna Adeno-Associated Virus 9 Expressing Iduronate-2-Sulfatase in Rhesus Macaques

Hunter syndrome is an X-linked recessive disease caused by deficiency of the lysosomal enzyme iduronate-2-sulfatase. The severe form of this progressive, systemic, and neurodegenerative disease results in loss of cognitive skills and early death. Several clinical trials are evaluating adeno-associated virus 9 for the treatment of neurodegenerative diseases using systemic or intrathecal lumbar administration. In large animals, administration via suboccipital puncture gives better brain transduction than lumbar administration. Here, we conducted a good laboratory practice-compliant investigational new drug-enabling study to determine the safety of suboccipital adeno-associated virus 9 gene transfer of human iduronate-2-sulfatase into nonhuman primates. Thirteen rhesus macaques received vehicle or one of two doses of vector with or without immunosuppression. We assessed in-life safety and immune responses. Animals were euthanized 90 days post-administration and sampled for histopathology and biodistribution. The procedure was well tolerated in all animals. Minimal mononuclear cerebrospinal fluid pleocytosis occurred in some animals. Asymptomatic minimal-to-moderate toxicity to some dorsal root ganglia sensory neurons and their associated axons occurred in all vector-treated animals. This study supports the clinical development of suboccipital adeno-associated virus 9 delivery for severe Hunter syndrome and highlights a potential toxicity that warrants monitoring in first-in-human studies.