Evaluation of enzyme dose and dose-frequency in ameliorating substrate accumulation in MPS IIIA Huntaway dog brain

J Inherit Metab Dis. 2015 Mar;38(2):341-50. doi: 10.1007/s10545-014-9790-8. Epub 2014 Nov 25.


Intracerebrospinal fluid (CSF) infusion of replacement enzyme is under evaluation for amelioration of disease-related symptoms and biomarker changes in patients with the lysosomal storage disorder mucopolysaccharidosis type IIIA (MPS IIIA; www.clinicaltrials.gov ; NCT#01155778; #01299727). Determining the optimal dose/dose-frequency is important, given the invasive method for chronically supplying recombinant protein to the brain, the main site of symptom generation. To examine these variables, we utilised MPS IIIA Huntaway dogs, providing recombinant human sulphamidase (rhSGSH) to young pre-symptomatic dogs from an age when MPS IIIA dog brain exhibits significant accumulation of primary (heparan sulphate) and secondary (glycolipid) substrates. Enzyme was infused into CSF via the cisterna magna at one of two doses (3 mg or 15 mg/infusion), with the higher dose supplied at two different intervals; fortnightly or monthly. Euthanasia was carried out 24 h after the final injection. Dose- and frequency-dependent reductions in heparan sulphate were observed in CSF and deeper layers of cerebral cortex. When we examined the amount of immunostaining of the general endo/lysosomal marker, LIMP-2, or quantified activated microglia, the higher fortnightly dose resulted in superior outcomes in affected dogs. Secondary lesions such as accumulation of GM3 ganglioside and development of GAD-reactive axonal spheroids were treated to a similar degree by both rhSGSH doses and dose frequencies. Our findings indicate that the lower fortnightly dose is sub-optimal for ameliorating existing and preventing further development of disease-related pathology in young MPS IIIA dog brain; however, increasing the dose fivefold but halving the frequency of administration enabled near normalisation of disease-related biomarkers.

Trial registration: ClinicalTrials.gov NCT01155778 NCT01299727.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomarkers / metabolism
  • Brain / drug effects*
  • Brain / enzymology
  • Brain / pathology
  • Disease Models, Animal
  • Dogs
  • Drug Administration Schedule
  • Drug Dosage Calculations
  • Enzyme Replacement Therapy*
  • Glycolipids / metabolism
  • Heparitin Sulfate / metabolism
  • Hydrolases / administration & dosage*
  • Infusions, Intraventricular
  • Lysosomal-Associated Membrane Protein 2 / metabolism
  • Mucopolysaccharidosis III / drug therapy*
  • Mucopolysaccharidosis III / enzymology
  • Mucopolysaccharidosis III / genetics
  • Mucopolysaccharidosis III / pathology
  • Recombinant Proteins / administration & dosage
  • Time Factors


  • Biomarkers
  • Glycolipids
  • Lysosomal-Associated Membrane Protein 2
  • Recombinant Proteins
  • Heparitin Sulfate
  • Hydrolases
  • N-sulfoglucosamine sulfohydrolase

Associated data

  • ClinicalTrials.gov/NCT01155778
  • ClinicalTrials.gov/NCT01299727