RecruitingOBSERVATIONAL

Effective Dosing of Burosumab in XLH

X-linked Hypophosphataemia (XLH) is a rare condition that affects bones and teeth because the body can't keep enough phosphate. This can lead to soft bones, pain, and stunted growth. Burosumab (Crysvita) is a newer medicine given by injection every two weeks to help manage XLH in children. Currently, the recommended starting dose is 0.8mg/kg, but some doctors believe that a lower dose might still be effective for some children. This study will look back at health records of about 200 children with XLH who are already taking Burosumab in England. The aim is to understand how different starting doses and ongoing doses of Burosumab affect children's health, their growth, and their blood tests, to help doctors find the best dose for each child.

At a glance

Status

Recruiting

Sponsor

University of Nottingham

Enrolment target

120

Start

03 Nov 2025

Estimated completion

01 Jul 2026

X-linked Hypophosphatemia (XLH)

What is this study about?

X-linked Hypophosphataemia, or XLH, is a rare condition that someone is born with. It means their body can't hold onto enough phosphate, a mineral vital for strong bones and teeth, and for giving our bodies energy. When phosphate levels are too low, bones can become soft, leading to problems like bowed legs, shorter height, and constant pain in bones and teeth.

In the past, children with XLH would take several phosphate supplements and vitamin D tablets multiple times a day. While this helped, many children continued to experience significant pain and difficulties, which affected their daily lives. Now, there's a medicine called Burosumab (Crysvita) that has become the standard treatment for children with XLH. It's given as an injection under the skin every two weeks.

Currently, the European Medicines Agency suggests a starting dose of 0.8mg/kg for Burosumab. However, doctors have noticed that some children might do well on a lower starting dose. This study aims to look closely at the information already in the health records of children with XLH who are being treated with Burosumab across different hospitals in England. The researchers want to see if starting with a lower dose works just as well for some children, and how different doses affect their growth and blood test results. This knowledge will help doctors decide the best dose for each child, ensuring they get the right amount of medicine without receiving more than necessary.

Key takeaways

Study focuses on children with X-linked Hypophosphataemia (XLH).
Investigating effective dosing of Burosumab (Crysvita).
Researchers are reviewing existing medical records only.
No new procedures or appointments needed for your child.
Aims to improve future treatment guidance for XLH patients.

Who may be eligible?

This study is looking at information for children and young people who have a specific type of bone condition called X-linked Hypophosphataemia (XLH). To be included, their XLH diagnosis must have been confirmed by a genetic test.

They also need to have been receiving Burosumab treatment under the care of a paediatric (children's) doctor for at least 12 months in a row. The children must have started this treatment before their 18th birthday. The study will look at their records from when they were between 2 and 18 years old.

If a young person later moved from children's care to adult care for their Burosumab treatment, the study will only use the information from when they were still being treated as a child.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Does your child have X-linked Hypophosphataemia (XLH)?
Was their XLH diagnosis confirmed by a genetic test?
Has your child been receiving Burosumab (Crysvita) treatment continuously for at least 12 months?
Did they start Burosumab treatment before their 18th birthday?
Is your child currently between 2 and 18 years old, or were they in this age range when receiving paediatric Burosumab?

Answer every question to see your result.

What does participation involve?

This study is different because you won't need to do anything new. It's not a trial where you receive new tests or medicines. Instead, researchers will look back at health information that's already in your child's medical records from their routine hospital visits. This includes their test results, growth measurements, and details about the Burosumab doses they received. There are no extra visits, assessments, or follow-up appointments required for this study. The researchers will simply collect data that has already been recorded as part of your child's regular care.

Potential risks and benefits

Since this study only involves looking at existing medical records, there are no direct risks to your child from taking part. They won't undergo any new procedures or treatments. The potential benefit is that the findings from this study could help doctors better understand the most effective way to dose Burosumab for other children with XLH in the future. This could lead to more personalised and effective treatment plans. As no new information is being collected directly from patients, there isn't a direct right to withdraw individual data once it's been anonymised, as it is already part of routine care records.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

Nottingham University Hospitals NHS Trust
Verified postcode
Nottingham, United Kingdom· Recruiting

Common questions

What is XLH?

XLH is a rare genetic condition where your body can't keep enough phosphate, which is important for strong bones and teeth.

What is Burosumab (Crysvita)?

Burosumab is a medicine given by injection every two weeks to treat XLH and help bones become stronger.

Will my child have to do anything extra for this study?

No, your child won't have to do anything extra. The study only looks at information already in their medical records.

Who can be included in this study?

Children aged 2 to 18 with XLH who have received Burosumab for at least a year are included.

How will this study help?

It will help doctors understand the best doses of Burosumab for children with XLH, leading to better treatment for others in the future.

How to find out more

James M Law, BMBS, PhD, MRCPCH

james.law@nottingham.ac.uk 01159249924 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.