A GLP-Compliant Toxicology and Biodistribution Study: Systemic Delivery of an rAAV9 Vector for the Treatment of Mucopolysaccharidosis IIIB

Abstract

No treatment is currently available for mucopolysaccharidosis (MPS) IIIB, a neuropathic lysosomal storage disease due to defect in α-N-acetylglucosaminidase (NAGLU). In preparation for a clinical trial, we performed an IND-enabling GLP-toxicology study to assess systemic rAAV9-CMV-hNAGLU gene delivery in WT C57BL/6 mice at 1 × 10(14) vg/kg and 2 × 10(14) vg/kg (n = 30/group, M:F = 1:1), and non-GLP testing in MPS IIIB mice at 2 × 10(14) vg/kg. Importantly, no adverse clinical signs or chronic toxicity were observed through the 6 month study duration. The rAAV9-mediated rNAGLU expression was rapid and persistent in virtually all tested CNS and somatic tissues. However, acute liver toxicity occurred in 33% (5/15) WT males in the 2 × 10(14) vg/kg cohort, which was dose-dependent, sex-associated, and genotype-specific, likely due to hepatic rNAGLU overexpression. Interestingly, a significant dose response was observed only in the brain and spinal cord, whereas in the liver at 24 weeks postinfection (pi), NAGLU activity was reduced to endogenous levels in the high dose cohort but remained at supranormal levels in the low dose group. The possibility of rAAV9 germline transmission appears to be minimal. The vector delivery resulted in transient T-cell responses and characteristic acute antibody responses to both AAV9 and rNAGLU in all rAAV9-treated animals, with no detectable impacts on tissue transgene expression. This study demonstrates a generally safe and effective profile, and may have identified the upper dosing limit of rAAV9-CMV-hNAGLU via systemic delivery for the treatment of MPS IIIB.

An Isolated Limb Infusion Method Allows for Broad Distribution of rAAVrh74.MCK.GALGT2 to Leg Skeletal Muscles in the Rhesus Macaque

“…NAGLU at 2 × 10 14 vg/kg, a dose 3.6 or 4 times larger than the two high doses in our ILI study, found 3.2 × 10 7 vg/μg genomic DNA in liver at 6 weeks post-treatment, in contrast to an average of 3.3 × 10 6 vg/μg for our study at 3 months post-treatment. 50 Thus, at least in these two comparisons (albeit with a different AAV serotype), there appears to be a 2.5- to 6-fold reduction in vector delivery to the liver, relative to dose, using ILI instead of i.v. delivery.…”

Superior In vivo Transduction of Human Hepatocytes Using Engineered AAV3 Capsid

“…However, AAV9 has a broad tissue tropism and transduces heart, skeletal muscle, and neurons in addition to liver. 47 In contrast, biodistribution studies in non-human primates show strong liver tropism of AAV3 and AAV3-ST following peripheral vein administration with minimal distribution to other organs (except for the spleen, which invariably takes up viral particles). 18 AAV5 vector has been used in a recent clinical trial for the rare inherited metabolic disorder porphyria.…”

Direct Intracranial Injection of AAVrh8 Encoding Monkey β-N-Acetylhexosaminidase Causes Neurotoxicity in the Primate Brain

“…A recent study using systemic delivery of AAV9 encoding another lysosomal enzyme, a-Nacetylglucosaminidase, to treat mucopolysaccharidosis (MPS) IIIB resulted in liver toxicity associated with transgene overexpression in wild-type but not MPS IIIB mice. 65 The difference in safety outcomes across and within species raises concerns about the predictive value of preclinical dose ranging and safety studies when translating AAV gene therapies from animals to humans.…”