General Information

Elaprase (idursulfase) is a purified form of the lysosomal enzyme human iduronate-2-sulfatase of recombinant DNA origin. It is designed to replace the natural enzyme, increasing catabolism of certain accumulated glycosaminoglycans (GAG), which abnormally accumulate in multiple tissue types in patients with mucopolysaccharidosis II (MPS-II, or Hunter syndrome).

Elaprase is specifically indicated for the treatment of Hunter syndrome in adults and children ages 5 and older. The drug has been shown to improve walking capacity in these subjects.

Elaprase is supplied as sterile, aqueous clear to slightly-opalescent colorless solution for intravenous infusion. Recommended initial dosing is 0.5 mg/kg administered via weekly infusion. The initial recommended infusion rate is 8 ml/hr for the first 15 minutes, which may be increased at 8/ml/hr increments at 15 minute intervals barring appearance of infusion reactions, to a maximum of 100 ml/hr. Total infusion duration is generally 1-3 hours, and should not exceed 8 hours. Infusions may be slowed, temporarily stopped, or discontinued for that dose if infusion reactions occur (see Side Effects, below).

Clinical Results

FDA Approval
FDA approval of Elaprase was based on the results of one clinical trial. This randomized, double-blind, placebo controlled trial enrolled 96 subjects with Hunter's Syndrom, aged 5-31 years. Subjects received Elaprase 0.5mg/kg every week, Elaprase 0.5mg/kg every other week or placebo. The treatment duration was 53 weeks. The primary efficacy endpoint was a score based on the change from baseline to week 53 in distance walked during a 6 minute walk test and the change in forced vital capacity percentages. The primary endpoints showed the greatest statistical significant difference between the weekly Elaprase treated group and the placebo group (p=0.0049). The subjects in the Elaprase weekly group showed a 35 meter mean increase in distance walked versus the placebo group. There was not a statistically significant difference in forced vital capacity percentages between the groups.

Ongoing Study Commitments

• Shire commits to long-term safety and efficacy data in an observational survey (the Hunter Outcome Survey, HOS) of patients with Hunter Syndrome being treated with Elaprase. In addition to clinical and laboratory tests that are part of standard medical care for patients with Hunter's Syndrome, the survey will collect data on patients from the six minute walk test, from a subset of centers that will have the training a facilities to collects the data in a standardized and reproducible manner, and urinary GAG levels approximately every 6 to 12 months for at least 15 years. Assessments and data collected in the HOS will include those listed in table 1 of the Hunter Outcome Survey summary protocol version 1.0, dated October 31, 2005 and in the Safety Specification and Pharmacovigilance Plan documented in the Elaprase BLA. For pediatric patients in the HOS, data to be collected will include standardized and replicated height, weight and head circumference in conjunction with deformity assessments and patients method of feeding. The survey will be designed to take advantage of any opportunity to evaluate the effect of Elaprase on female reproduction, pregnancy and lactation. The HOS data will be analyzed at yearly intervals and the results will be submitted in annual reports for BB-IND.
  Protocol Submission: by November 2006
  Study start: March 2007
  Final report submission: September 2022
• Shire has agreed to conducting a study to evaluate the pharmacokinetics, pharmacodynamis and safety in at least 18 children 5 years of age and under treated with Elaprase for at least 6 months. In this population, pharmacodynamics will include urinary GAG levels and changes in liver and spleen volumes. The study will assess routine developmental milestones and growth. The study will collect data on respiratory infections, surgical interventions (e.g., PE tubes and adenoidectomy), hearing loss, serious or severe infusion reactions, and other serious adverse events. The study may be conducted as a separate study or as a sub-study under a special protocol within the Hunter Outcome Survey.
  Protocol Submission: November 2006
  Study Start: March 2007
  Final Report Submission: June 2009
• Shire has agreed to submit the final study complete study TKT024EXT, titled "An Open Label Extension study of TKT024 Evaluating Long-term Safety and Clinical Outcomes of MPS II Patients Receiving I2S Enzyme Replacement Therapy".
  Study Completion: December 2007
  Final Report Submission: August 2008

Side Effects

Adverse events associated with the use of Elaprase may include, but are not limited to, the following:

• pyrexia
• headache
• arthralgia
• limb pain
• pruitis
• hypertension
• malaise
• visual disturbance

In addition, Elaprase was shown to cause anaphylactiod reactions in some patients during infusions. It is contraindicated in patients with comprised respiratory function or acute respiratory disease.

Mechanism of Action

Hunter's Syndrome is an X-linked recessive disease caused by insufficient levels of the lysosomal enzyme iduronate-2-sulfatase. This enzyme cleaves the terminal 2-O-sulfate moieties from the glycosaminoglycans (GAG) dermatan sulfate and heparan sulfate. Due to the missing or defective iduronate-2-sulfatase enzyme in patients with Hunter's Syndrome, GAG progressively accumulate in the lysosomes of a variety of cells, leading to cellular engorgement, organomegaly, tissue destruction and organ system dysfunction. Treatment of Hunter's Syndrome patients with Elaprase provides exogenous enzyme for uptake into cellular lysosomes. Mannose-6-phosphate (M6P) residues on the oligosaccharide chains allow specific binding of the enzymes to the M6P receptors on the cell surface, leading to cellular internalization of the enzyme, targeting to intracellular lysosomes and subsequent catabolism of accumulated GAG.

Literature References

Muenzer J, Wraith JE, Beck M, Giugliani R, Harmatz P, Eng CM, Vellodi A, Martin R, Ramaswami U, Gucsavas-Calikoglu M, Vijayaraghavan S, Wendt S, Puga A, Ulbrich B, Shinawi M, Cleary M, Piper D, Conway AM, Kimura A A phase II/III clinical study of enzyme replacement therapy with idursulfase in mucopolysaccharidosis II (Hunter syndrome). Genetics in medicine : official journal of the American College of Medical Genetics 2006 Aug;8(8):465-73.