Idursulfase — Complete Research Guide (2026)

Last updated 2026-06-30

What is Idursulfase?

Idursulfase (brand name Elaprase) is a recombinant human iduronate-2-sulfatase approved as enzyme replacement therapy for mucopolysaccharidosis type II (MPS II, Hunter syndrome). It was approved by the US FDA in 2006 and by the EU (EMA) in 2007.

Evidence includes a pivotal randomized placebo-controlled trial, a long-term open-label extension, and independent Cochrane and other systematic reviews, so it is supported by a moderate-to-high level of human clinical evidence.

It is a prescription-only biologic administered under specialist supervision.

How does Idursulfase work?

Idursulfase is a recombinant form of iduronate-2-sulfatase, the lysosomal enzyme deficient in Hunter syndrome.

Given intravenously, it is internalized via mannose-6-phosphate receptors and cleaves the terminal 2-O-sulfate groups of the glycosaminoglycans dermatan sulfate and heparan sulfate, reducing their lysosomal accumulation in peripheral tissues.

What does the research say about Idursulfase?

• In the pivotal 52-week randomized trial, weekly idursulfase improved a combined endpoint of 6-minute walk distance and pulmonary function versus placebo in patients with Hunter syndrome. ^[1]
• A long-term open-label extension showed durable improvements in walking capacity, liver and spleen volume, and pulmonary measures over multiple years of treatment. ^[2]
• Systematic review evidence supports somatic (non-neurological) benefits, while confirming intravenous idursulfase does not treat central nervous system disease. ^[3]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

• [1] A phase II/III clinical study of enzyme replacement therapy with idursulfase in mucopolysaccharidosis II (Hunter syndrome) — Muenzer J et al., Genetics in Medicine 2006. (Randomized, double-blind, placebo-controlled trial)
• [2] Long-term, open-labeled extension study of idursulfase in the treatment of Hunter syndrome — Muenzer J et al., Genetics in Medicine 2011. (Open-label long-term extension study)
• [3] Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome) — da Silva EM et al., Cochrane Database of Systematic Reviews 2016. (Cochrane systematic review)
• [4] Enzyme replacement therapy for the treatment of Hunter disease: A systematic review with narrative synthesis and meta-analysis — Wikman-Jorgensen PE et al., Molecular Genetics and Metabolism 2020. (Systematic review and meta-analysis)
• [5] CNS penetration of intrathecal-lumbar idursulfase in the monkey, dog and mouse: implications for neurological outcomes of lysosomal storage disorder — Calias P et al., PLoS One 2012. (Preclinical (animal) pharmacology study)

Dosing context

For context only and not as medical advice, idursulfase is typically administered as a weekly intravenous infusion at about 0.5 mg/kg, with the infusion rate titrated and patients monitored for reactions.

Exact dosing, premedication, and monitoring are determined by the treating specialist.

Side effects & safety profile

Infusion-related reactions (such as fever, headache, urticaria, flushing, and bronchospasm) are common, and serious anaphylactoid/hypersensitivity reactions can occur, so infusions require monitoring and often premedication.

Many patients develop anti-idursulfase antibodies, including neutralizing antibodies, which can be more frequent and clinically relevant in patients with certain (complete gene deletion/nonsense) genotypes.

Because standard intravenously administered idursulfase does not cross the blood-brain barrier, it does not address the neurocognitive manifestations of severe Hunter syndrome.

Stacking & combinations

It is used as a single-agent enzyme replacement therapy; investigational intrathecal formulations for CNS disease are separate and not a substitute for the approved intravenous product.

Finding Idursulfase vendors

User reviews

Frequently asked questions

References

1. [1] A phase II/III clinical study of enzyme replacement therapy with idursulfase in mucopolysaccharidosis II (Hunter syndrome) — Muenzer J et al., Genetics in Medicine 2006. PMID: 16912578. View sourceStudy: Randomized, double-blind, placebo-controlled trialWeekly idursulfase significantly improved a composite of 6-minute walk distance and forced vital capacity over 52 weeks.
2. [2] Long-term, open-labeled extension study of idursulfase in the treatment of Hunter syndrome — Muenzer J et al., Genetics in Medicine 2011. PMID: 21150784. View sourceStudy: Open-label long-term extension studyContinued idursulfase produced sustained improvements in walking, organ volumes, and pulmonary function over extended follow-up.
3. [3] Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome) — da Silva EM et al., Cochrane Database of Systematic Reviews 2016. PMID: 26845288. View sourceStudy: Cochrane systematic reviewFound short-term benefit on walking and pulmonary function but limited long-term randomized evidence and no CNS effect.
4. [4] Enzyme replacement therapy for the treatment of Hunter disease: A systematic review with narrative synthesis and meta-analysis — Wikman-Jorgensen PE et al., Molecular Genetics and Metabolism 2020. PMID: 32773276. View sourceStudy: Systematic review and meta-analysisSynthesized evidence supporting somatic benefits of idursulfase while noting heterogeneity and lack of neurological improvement.
5. [5] CNS penetration of intrathecal-lumbar idursulfase in the monkey, dog and mouse: implications for neurological outcomes of lysosomal storage disorder — Calias P et al., PLoS One 2012. PMID: 22279584. View sourceStudy: Preclinical (animal) pharmacology studyDemonstrated in animals that intrathecal, but not standard intravenous, delivery achieves CNS enzyme exposure.