Wednesday, October 19, 2016

Gene therapy for Sanfilippo syndrome

No treatment is currently available for mucopolysaccharidosis (MPS) III, a group of four rare, autosomal recessive neuropathic lysosomal storage diseases, also known as Sanfilippo syndrome. However, researchers at Nationwide Children’s Hospital have developed effective adeno-associated viral (AAV)-based gene therapy approaches, targeting the root cause of the disease, for the treatment of MPS IIIA and MPS IIIB.

An interdisciplinary translational research team has also been formed at Nationwide Children’s to bring these gene therapy approaches to clinical trials in patients. The team has recently published two studies in preparation.

The first, a toxicology study in Human Gene Therapy Clinical Development, demonstrates a generally safe and effective profile for systemic AAV gene therapy. The second, in Molecular Genetics and Metabolism, is a natural history of MPS IIIA and IIIB in 25 patients, designed to identify appropriate methods to measure outcomes of a gene therapy trial.

“Caused by a single gene defect, most of the children with this disease do not reach adulthood,” says Kevin Flanigan, MD, attending neurologist at Nationwide Children’s, principal investigator in the Center for Gene Therapy in The Research Institute, and co-author of the study. “This investigational gene therapy approach represents a new treatment paradigm for addressing this relentlessly progressing disease.”

“Importantly, our toxicology studies also identified the upper dosing limit of systemic AAV gene delivery for the treatment of MPS IIIB,” says Haiyan Fu, PhD, lead author of the study and principal investigator in the Center for Gene Therapy. “This will guide safe clinical application in humans.”

Douglas McCarty, PhD, principal investigator in the Center for Gene Therapy and study co-author, notes that the progressive neurodegeneration of MPS IIIB, which begins in early childhood, necessitates effective gene delivery to the brain.

“Our approach is to employ intravenous injection of an AAV serotype that crosses the blood-brain-barrier,” explains Dr. McCarty. “We have also done numerous studies in mice to determine how far into the disease progression we can still achieve possible therapeutic benefits.”

The team has recently received two investigational new drug (IND) approvals from the FDA for Phase 1/2 gene therapy clinical trials for patients with MPS IIIA (ongoing) and MPS IIIB (to be initiated), both at Nationwide Children’s.



  1. Meadows AS, Duncan FJ, Camboni M, Waligura K, Montgomery CL, Zaraspe K, Naughton BJ, Bremer WG, Shilling C, Walker C, Bolon B, Flanigan K, McBride KL, McCarty DM, Fu H. A GLP-compliant toxicology and biodistribution study: systemic delivery of a rAAV9 vector for the treatment of mucopolysaccharidosis IIIB. Hum Gene Ther Clin Dev. 2015 Dec 9. [Epub ahead of print]

    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 1x1014vg/kg and 2x1014vg/kg (n=30/group, M:F=1:1), and non-GLP testing in MPS IIIB mice at 2x1014vg/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 2x1014vg/kg cohort, which was dose-dependent, sex-associated and genotype-specific, likely due to hepatic rNAGLU over-expression. Interestingly, a significant dose response was observed only in the brain and spinal cord, whereas in the liver at 24-wk 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.

  2. Truxal KV, Fu H, McCarty DM, McNally KA, Kunkler KL, Zumberge NA, Martin L, Aylward SC, Alfano LN, Berry KM, Lowes LP, Corridore M, McKee C, McBride KL, Flanigan KM. A prospective one-year natural history study of mucopolysaccharidosis types IIIA and IIIB: Implications for clinical trial design. Mol Genet Metab. 2016 Aug 18. pii: S1096-7192(16)30184-6. doi:10.1016/j.ymgme.2016.08.002. [Epub ahead of print]

    Mucopolysaccharidosis type III is a group of four autosomal recessive enzyme deficiencies leading to tissue accumulation of heparan sulfate. Central nervous system disease is prominent, with initial normal development followed by neurocognitive decline leading to death. In order to define outcome measures suitable for gene transfer trials, we prospectively assessed disease progression in MPS IIIA and IIIB subjects >2years old at three time points over one year (baseline, 6 and 12months). Fifteen IIIA (9 male, 6 female; age 5.0±1.9years) and ten IIIB subjects (8 male, 2 female; age 8.6±3years) were enrolled, and twenty subjects completed assessments at all time points. Cognitive function as assessed by Mullen Scales maximized at the 2.5 to 3year old developmental level, and showed a significant age-related decline over a 6month interval in three of five subdomains. Leiter nonverbal IQ (NVIQ) standard scores declined toward the test floor in the cohort by 6 to 8years of age, but showed significant mean declines over a 6month interval in those <7years old (p=0.0029) and in those with NVIQ score≥45 (p=0.0313). Parental report of adaptive behavior as assessed by the Vineland-II composite score inversely correlated with age and showed a significant mean decline over 6month intervals (p=0.0004). Abdominal MRI demonstrated increased volumes in liver (mean 2.2 times normal) and spleen (mean 1.9 times normal) without significant change over one year; brain MRI showed ventriculomegaly and loss of cortical volume in all subjects. Biochemical measures included urine glycosaminoglycan (GAG) levels, which although elevated showed a decline correlating with age (p<0.0001) and approached normal values in older subjects. CSF protein levels were elevated in 32% at enrollment, and elevations of AST and ALT were frequent. CSF enzyme activity levels for either SGSH (in MPS IIIA subjects) or NAGLU (in MPS IIIB) significantly differed from normal controls. Several other behavioral or functional measures were found to be uninformative in this population, including timed functional motor tests. Our results suggest that cognitive development as assessed by the Mullen and Leiter-R and adaptive behavior assessment by the Vineland parent interview are suitable functional outcomes for interventional trials in MPS IIIA or IIIB, and that CSF enzyme assay may be a useful biomarker to assess central nervous system transgene expression in gene transfer trials.