Enzyme replacement for MPS I (Hurler)
Laronidase
A regular drip that replaces the missing enzyme in MPS I (Hurler, Hurler-Scheie and Scheie), an inherited lysosomal storage disorder.
What is Laronidase?
Laronidase is an enzyme replacement therapy for mucopolysaccharidosis type I (MPS I), which includes the Hurler, Hurler-Scheie and Scheie forms. In MPS I, complex sugars build up because an enzyme is missing, affecting many parts of the body such as the joints, heart, airways and liver. Laronidase is given as a slow drip into a vein, usually weekly and for life, at a specialist metabolic centre. It does not cross into the brain, so it does not treat the cognitive features. The most common issue is an infusion reaction, managed with pre-medication and by slowing the drip.
Education and reference only. This is a plain-language guide to Laronidase — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Laronidase is a man-made version of alpha-L-iduronidase, the enzyme that people with MPS I lack. MPS I is a rare inherited 'lysosomal storage' disorder, in which complex sugars called glycosaminoglycans that should be broken down build up in cells across the body. This can affect the joints, bones, heart, airways, liver and other organs, and ranges from the more severe Hurler form to the milder Scheie form. Laronidase (brand name Aldurazyme) is given as a drip into a vein and is started and supervised by a specialist metabolic team.
How it works
Laronidase supplies the working enzyme that people with MPS I are missing, so the complex sugars building up in cells can be broken down. Given regularly into a vein, it helps reduce these deposits in tissues such as the liver and around the joints and airways, which can improve walking distance and breathing and ease some physical symptoms over time. Importantly, it does not cross from the blood into the brain, so it does not treat the learning and thinking (cognitive) features of the more severe forms. Because the body keeps producing the sugars, the enzyme must be replaced repeatedly, so treatment is lifelong.
Company & origin
Originated / developed by: Specialist (Sanofi).
A laboratory-made copy of a missing enzyme, given by drip in UK specialist metabolic centres to treat the inherited condition mucopolysaccharidosis type I.
Practical use
How to take Laronidase
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as a slow drip into a vein at a specialist centre, usually weekly, by trained staff.
- Pre-medication, such as an antihistamine or paracetamol, may be given to reduce the chance of an infusion reaction.
- Tell the staff at once if you or your child develops flushing, fever, a rash, sickness or breathing trouble during the drip.
- Keep to the weekly schedule, as missing infusions lets the complex sugars build up again.
- Attend the wider checks of the heart, airways, joints and growth that go alongside the infusions.
Weighing it up
Advantages & disadvantages of Laronidase
Advantages
- Replaces the missing enzyme and can improve walking distance, breathing and some physical symptoms.
- Can shrink an enlarged liver and ease pressure on the airways and joints over time.
- A long-established treatment that helps many people with MPS I function better day to day.
Disadvantages
- Does not cure MPS I and must be given by drip for life.
- Does not cross into the brain, so it does not treat the cognitive features of the severe form.
- Commonly causes infusion reactions needing pre-medication and monitoring.
Practical use
Good to know
Laronidase controls the physical (non-brain) features of MPS I but does not cure it, and because it does not cross into the brain it does not treat the cognitive features; for some children with the severe form, a stem cell (bone marrow) transplant may be considered separately by specialists. The drips continue for life and are arranged through a specialist metabolic centre. The most common issue is an infusion reaction, with flushing, fever, chills, headache, a rash or feeling sick during or soon after the drip; pre-medication and a slower rate often help. Some people make antibodies to the enzyme, which the team monitors. Care usually involves a wider team for the heart, airways, joints and bones.
Who should not take it / use with caution
- People who have had a severe allergic reaction to laronidase should not receive it again unless specialists advise.
- It is used with extra care in those who develop antibodies that reduce its effect or worsen reactions.
- Other illnesses, pregnancy or breastfeeding should be discussed with the metabolic team before continuing.
Monitoring
- Regular checks of breathing, walking distance, the heart, joints, liver size and growth to track response.
- Watching for infusion reactions during and after each drip and for antibodies over time.
- Ongoing specialist review, including whether a stem cell transplant is relevant for severe forms in children.
Side effects
- Infusion reactions such as flushing, fever, chills, headache, rash or nausea are the most common.
- Less commonly, a fast heartbeat, abdominal pain or breathing changes during or after the drip.
- Rarely, a serious allergic reaction, which is why infusions are given where staff can respond quickly.
Key interactions
- No major routine medicine interactions are well established, but tell the team everything you or your child takes.
- Care for the heart, airways and joints is coordinated by the specialist centre alongside the infusions.
- Any new medicines should be mentioned so they can be reviewed with the enzyme treatment.
Available as: A drip (infusion) into a vein, given at a specialist centre.
Answers
Laronidase: frequently asked questions
Does laronidase treat the brain symptoms of MPS I?
No. It does not cross from the blood into the brain, so it does not treat the learning and thinking features; for some children a stem cell transplant may be considered separately.
Will it cure MPS I?
No. It replaces the missing enzyme and helps the physical features, but it does not cure the condition, so the drips are needed for life.
How often is the drip given?
It is usually given weekly at a specialist centre, though your team will confirm the schedule that is right for you or your child.
Why might there be a reaction during the infusion?
Infusion reactions such as flushing, fever or a rash are common; pre-medication and slowing the drip usually help settle them.
Who looks after the rest of the condition?
MPS I affects many parts of the body, so a wider specialist team helps with the heart, airways, joints and bones alongside the enzyme drips.
Authoritative sources
- BNF
- NICE CKS
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