Feasibility and Safety of Systemic rAAV9-hNAGLU Delivery for Treating Mucopolysaccharidosis IIIB: Toxicology, Biodistribution, and Immunological Assessments in Primates

Abstract

No treatment is currently available for mucopolysaccharidosis (MPS) IIIB, a neuropathic lysosomal storage disease caused by autosomal recessive defect in a-N-acetylglucosaminidase (NAGLU). In anticipation of a clinical gene therapy treatment for MPS IIIB in humans, we tested the rAAV9-CMV-hNAGLU vector administration to cynomolgus monkeys (n = 8) at 1E13 vg/kg or 2E13 vg/kg via intravenous injection. No adverse events or detectable toxicity occurred over a 6-month period. Gene delivery resulted in persistent global central nervous system and broad somatic transduction, with NAGLU activity detected at 2.9-12-fold above endogenous levels in somatic tissues and 1.3-3-fold above endogenous levels in the brain. Secreted rNAGLU was detected in serum. Low levels of preexisting anti-AAV9 antibodies (Abs) did not diminish vector transduction. Importantly, high-level preexisting anti-AAV9 Abs lead to reduced transduction in liver and other somatic tissues, but had no detectable impact on transgene expression in the brain. Enzyme-linked immunoabsorbent assay showed Ab responses to both AAV9 and rNAGLU in treated animals. Serum anti-hNAGLU Abs, but not anti-AAV9 Abs, correlated with the loss of circulating rNAGLU enzyme. However, serum Abs did not affect tissue rNAGLU activity levels. Weekly or monthly peripheral blood interferon-c enzyme-linked immunospot assays detected a CD4 + T-cell (Th-1) response to rNAGLU only at 4 weeks postinjection in one treated subject, without observable correlation to tissue transduction levels. The treatment did not result in detectable CTL responses to either AAV9 or rNAGLU. Our data demonstrate an effective and safe profile for systemic rAAV9-hNAGLU vector delivery in nonhuman primates, supporting its clinical potential in humans.

Gene therapy for Mucopolysaccharidoses

“…After a single systemic gene delivery of rAAV9 in non-human primates, pre-existing anti-AAV9 antibody at low level did not diminish vector transduction. However, high level pre-existing anti-AAV9 antibody leds to the reduction of vector transduction in somatic tissues, but had less impact on transduction in the CNS, indicating that CNS entry is less sensitive to pre-existing anti-AAV9 antibody [82]. These studies led to use of AAV antibody titer as a criterion of MPS patient eligibility to enter clinical trials of gene therapy.…”

“…Several studies have shown that systemic delivery of rAAV8 or rAAV9 containing the deficient gene cause elevation of lysosomal enzyme activity in CNS lesions and correction of disease progression in mouse models of MPS IIIA [90–93] and MPS IIIB [82,94–96]. Fu et al showed that a single IV administration of a scAAV9 vector encoding human N-sulfoglucosamine sulfohydrolase (hSGSH) (5e 12 vg/kg) in an MPS IIIA model mouse significantly improved behavior performance and survival rate [93] Improvements were best when the vector was administered at an early stage of disease, but these phenotypes were also partially corrected when treatment was delayed until mice showed intermediate progression of disease.…”

“…However, there is limited information about the length of gene expression in MPS patients after AAV-mediated gene therapy. Murrey et al showed that NAGLU activity was detected at 1.3–3 fold above endogenous levels in the brain after 6 months post-injection of single systemic administration of rAAV9 gene vector in non-human primates [82]. A recent clinical trial of MPS IIIB reported that CSF NAGLU activity was detected at 15–20% of that in unaffected children with MPS IIIB after 30 months treatment of IC rAAV5 gene therapy [99].…”

Gene Therapy for the Nervous System: Challenges and New Strategies

“…Most likely the answer is that it will depend on the neurological disease and therapeutic mechanism. For instance, in LSDs where the entire CNS is involved, the ideal approach is to have dispersed expression of the missing lysosomal enzymes by systemic delivery of AAV9 vectors [128,129]. Some degree of enzyme overexpression will be required to drive its secretion and uptake in non-transduced cells for correction of the lysosomal storage phenotype.…”

Neuronopathic Types of Mucopolysaccharidoses: Pathogenesis and Emerging Treatments

“…В недавних исследованиях на экспериментальных животных была показана возможность непосредствен-ной трансдукции клеток ЦНС и, соответственно, повы-шения активности фермента в клетках головного мозга при внутривенном введении аденоассоциированного вирусного вектора серотипа 9 (AAV9), экспрессирующего фермент ␣-N-ацетилглюкозаминидазу, дефицит которого приводит к развитию МПС IIIB [39].…”