title: Enzyme replacement therapy in patients who have mucopolysaccharidosis I and are younger than 5 years: results of a multinational study of recombinant human alpha-L-iduronidase (laronidase).
abstract: OBJECTIVE
  Our objective was to evaluate the safety, pharmacokinetics, and efficacy of laronidase in young, severely affected children with mucopolysaccharidosis I.
  
  
  METHODS
  This was a prospective, open-label, multinational study of 20 patients who had mucopolysaccharidosis I and were <5 years old (16 with Hurler syndrome, 4 with Hurler-Scheie syndrome) and were scheduled to receive intravenous laronidase at 100 U/kg (0.58 mg/kg) weekly for 52 weeks. Four patients underwent dosage increases to 200 U/kg for the last 26 weeks because of elevated urinary glycosaminoglycan levels at week 22.
  
  
  RESULTS
  Laronidase was well tolerated at both dosages. Investigators reported improved clinical status in 94% of patients at week 52. The mean urinary glycosaminoglycan level declined by approximately 50% at week 13 and was sustained thereafter. A more robust decrease in urinary glycosaminoglycan was observed in patients with low antibody levels and those who were receiving the 200 U/kg dosage. On examination, the liver edge was reduced by 69.5% in patients with a palpable liver at baseline and week 52 (n = 10). The proportion of patients with left ventricular hypertrophy decreased from 53% to 17%. Global assessment of sleep studies showed improvement or stabilization in 67% of patients, and the apnea/hypopnea index decreased by 5.8 events per hour (-8.5%) in those with abnormal baseline values. The younger patients with Hurler syndrome (<2.5 years) and all 4 patients with Hurler-Scheie syndrome showed normal mental development trajectories during the 1-year treatment period.
  
  
  CONCLUSIONS
  Laronidase seems to be well tolerated and to provide clinical benefit in patients who have severe mucopolysaccharidosis I and are <5 years old. Enzyme replacement therapy is not curative and may not improve all affected organs and systems in individuals when irreversible changes have developed. The long-term clinical outcome and effects of antibodies and laronidase dosing on glycosaminoglycan reduction warrant additional investigation.
authors.affiliation: Royal Manchester Children's Hospital, Willink Biochemical Genetics Unit, Hospital Road, Pendlebury, Manchester M27 1HA, United Kingdom. ed.wraith@cmmc.nhs.uk
authors.forename: J Edmond
authors.initials: JE
authors.lastname: Wraith
authors.forename: Michael
authors.initials: M
authors.lastname: Beck
authors.forename: Roderick
authors.initials: R
authors.lastname: Lane
authors.forename: Ans
authors.initials: A
authors.lastname: van der Ploeg
authors.forename: Elsa
authors.initials: E
authors.lastname: Shapiro
authors.forename: Yong
authors.initials: Y
authors.lastname: Xue
authors.forename: Emil D
authors.initials: ED
authors.lastname: Kakkis
authors.forename: Nathalie
authors.initials: N
authors.lastname: Guffon
mesh_terms: D002657:Child Development; D002675:Child, Preschool; D005260:Female; D006025:Glycosaminoglycans / Q000652:urine; D006801:Humans; D007068:Iduronidase / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology / Q000493:pharmacokinetics; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D007262:Infusions, Intravenous; D008099:Liver / Q000473:pathology; D008297:Male; D008059:Mucopolysaccharidosis I / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology / Q000493:pharmacokinetics
chemical_list: D006025:Glycosaminoglycans; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D007068:Iduronidase