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Burosumab and XLH

Burosumab is a relatively new treatment, which has been fully approved as an effective treatment for both children and adults. It is the only treatment that deals with the root cause of X-linked hypophosphataemia.

In people with XLH, the hormone fibroblast growth factor 23 (FGF23) is overactive, which signals to decrease the phosphate in the blood, resulting in poor bone mineralisation. Burosumab (marketed as Crysvita) is a monoclonal antibody that suppresses the activity of fibroblast growth factor 23 (FGF23). By suppressing FGF23, burosumab normalises the phosphate levels in the blood, which helps bones and teeth to form properly.

Burosumab has been licensed for use in Europe since February 2018, but in order for it to be made available on the NHS a Health Technology Assessment (HTA) is necessary. This is a technical process to demonstrate efficacy and value for money which follows different paths according to country and other factors. Below we summarise the specific rulings of different HTAs, all of which XLH UK have contributed to.

In summary, the excellent news is that, since July 2024, XLH patients of all ages are eligible for burosumab across all four nations of the UK.

Use of Burosumab for Children In UK 

Burosumab is recommended for treating XLH in children with radiographic evidence of bone disease aged 1 year and over, and in young people with growing bones.

The National Institute for Health and Care Excellence (NICE) in England recommended the use of burosumab for children in October 2018. Therefore, this can be prescribed on the NHS in England, Wales, HSC in Northern Ireland and the NCPE in the Republic of Ireland. The prescription and treatment plan is managed by a paediatrician once the diagnosis is confirmed. In Scotland the Scottish Medicines Consortium (SMC) has a slightly different process, but the outcome is the same. On 15th January 2024, after three years evaluation, the SMC confirmed access to burosumab (marketed as Crysvita) for the treatment of XLH in children and adolescents aged 1 to 17 years with radiographic evidence of bone disease.

Burosumab is administered via subcutaneous injection, typically every 2-weeks for children. The British Paediatric and Adolescent Bone Group (BPABG) recommend that the starting dose is 0.4 mg/kg. After commencing treatment, blood phosphate levels are typically monitored every 2 weeks during the first month, every 4 weeks for the following 2 months and thereafter as appropriate. Treatment can begin in children aged 1 year and can continue until the bones stop growing.

Reference: Padidela R, Cheung MS, Saraff V, Dharmaraj P. Clinical guidelines for burosumab in the treatment of XLH in children and adolescents: British paediatric and adolescent bone group recommendations. Endocr Connect. 2020 Oct; 9(10):1051-1056. doi: 10.1530/EC-20-0291. PMID: 33112809; PMCID: PMC7707830.

Use of Burosumab for Adults In UK 

As the marketing authorisation for the use of burosumab in England, Wales, Scotland, Ireland and Northern Ireland was originally for use in children with XLH, it excluded using burosumab in adults with XLH. 

England, Wales and Northern Ireland: On June 24th, 2024 NICE amended their recommendations from the draft guidance issued in November 2023. On the strength of evidence submitted by clinicians, XLH UK and the patient community, the guidance now recommends access to burosumab (marketed as Crysvita) to treat adults who have a confirmed diagnosis of XLH. Patients already on the early access trial will remain on burosumab. Other patients will need to be assessed by a specialist in metabolic bone disease.

It is likely that it will take some time for specialist centres to implement the new guidance. There is a list of Frequently Asked Questions about implementation at the bottom of this page. Patients can help to make their GPs aware of the new guidance and request referral to a specialist centre.  XLH UK has produced a map of specialists of which we are aware that you can find here.

Scotland: In 2023, the SMC recommended the use of burosumab in adults. This means that both children and adults can access burosumab from the NHS in Scotland that have a confirmed diagnosis. The recommendation for adults was made through the ultra-orphan pathway, which is used for medicines for very rare diseases. This pathway allows people with XLH to access burosumab while more data is collected to support its effectiveness. The SMC will review this evidence in three years to make a final decision on its routine use. 

Health Technology Assessments (HTA) in UK

There are different appraisal bodies across the UK. The guidance for England is highly influential across the UK.

Once a new treatment has a license, drug appraisal bodies weigh up the price a company has asked for against the clinical trial and other relevant data. They then recommend whether the drug will be clinically- and cost-effective for the NHS, in the context of available budget. 

The NHS is legally obliged to fund drugs recommended by these bodies. However, it also works the other way. If a drug is not recommended, then the NHS is not obliged to fund it. 

Implementation of 2024 NICE guidance FAQs

How do adults with X-linked hypophosphataemia access burosumab?

In the UK burosumab (marketed as Crysvita) can only be prescribed by an NHS specialist such as a rheumatologist or endocrinologist, typically with an interest in metabolic bone. Please visit our YouTube channel to watch our webinar about burosumab.

What is the expected timeframe for implementation of the new guidelines?

Burosumab is scheduled to be commissioned within 3 months of final NICE Guidance being issued, but it may take additional time for registration and supply to be set up in your area. XLH UK is working with clinical experts and Metabolic Support UK to expedite new guidelines which will facilitate the roll-out of burosumab across the NHS.

Should those already receiving burosumab on the Early Access Trial expect any changes?

At the time of writing, those already on burosumab are not expecting changes to their current care.

 

How do I get burosumab if I’m already under the care of a specialist?

Please continue to attend your scheduled appointments as normal and discuss your XLH symptoms with your specialist. If not already known, your specialist may want to confirm your PHEX mutation before making the recommendation to start burosumab.

How do I get referred to a specialist?

Please contact your local GP, as they will likely refer you to your nearest metabolic bone clinic. You can find a list of specialists here.

I was on burosumab but taken off it, can I go back on it?

If you were taken off burosumab because you moved from being classified as a child to an adult, you should talk to your specialist to determine whether you should go back on the treatment. If you came off the trial for other reasons, there is no change.

I’m doing well on phosphate, will my treatment change?

Please ensure that a specialist is monitoring your symptoms, phosphate dosing and blood work. Your treatment may not change if you are tolerating your current treatment plan.

I am thinking of starting a family. What is the recommendation?

It is important that you stop burosumab and inform your specialist if you are trying for a baby or are breastfeeding.

What are the side effects of taking burosumab?

Please share any concerns with your clinical specialist.

Reported side effects are back pain; constipation; dizziness; headaches; increased risk of infection; movement disorders; muscle spasms. In many cases these have subsided as doses are adjusted.

I have hypophosphataemia which is not due to XLH, can I request burosumab?

NICE marketing authorisation for burosumab is only for use in X-linked hypophosphataemia.

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