This article was first published on healthandcare.scot

The one in 50,000 people in Scotland thought to be living with a life-long genetic condition that impacts their bones, muscles and joints can now access the only therapy that targets the underlying cause of their condition.

Scotland’s medicine gatekeeper, the Scottish Medicines Consortium (SMC), has today accepted burosumab (brand name Crysvita®), a treatment addressing the underlying physiological processes of the rare condition.

Burosumab will help people with X-linked hypophosphatemia (XLH), a lifelong and progressive condition that can result in dental problems and increased risk of osteoporosis and early osteoarthritis.

Adults with XLH typically experience debilitating bone, joint and muscle symptoms affecting most areas of their body, resulting in pain, stiffness and fatigue that severely limit physical function and mobility.

Professor Stuart Ralston, Professor of Rheumatology at the University of Edinburgh, says the drug offers hope for adults with the debilitating condition:

“Until now, treatment options for adults living with symptomatic XLH have been limited. This is why it is excellent news that these patients will now be able to access a treatment that not only tackles the symptoms of XLH, but also targets the underlying cause of this rare, debilitating disease. I am excited to see the impact Crysvita has on eligible adults in Scotland.”

Scotland will be the first country in the UK to provide adults with XLH access to burosumab, through its ultra-orphan medicines pathway.

Introduced in 2018, the innovative pathway helps medicines for rare diseases become available in Scotland and continues to enable faster access to new medicines for patients with rare diseases which affect fewer than 1 in 50,000 people.

People with XLH have gene mutations which impact phosphate regulation, resulting in excessively low level of phosphate – a key mineral for maintaining healthy bones and teeth, muscle function and energy levels.

While it is usually passed down from a parent who carries the ‘defective gene’, XLH can sometimes appear in individuals with no family history.

Burosumab has been accepted for use following an initial assessment of the case presented by Japanese pharmaceutical company, Kyowa Kirin.

Due to low levels of people with the condition, research on its efficacy is ongoing and findings will be reviewed in three years before SMC decides whether burosumab will be adopted for routine use in NHS Scotland.

SMC Chairman, Mark MacGregor, said:

 “Adults will now gain access to burosumab while the company gathers additional evidence to inform a decision in three years. X-linked hypophosphataemia is a chronic and severely debilitating condition that causes pain and fatigue and is life limiting for patients.

“The costs of burosumab are very high relative to the identified benefits and this additional time will give the company the opportunity to provide greater certainty around the benefits for patients.”

Alongside high cost, the SMC has raised concerns about long-term benefits as the most robust, double-blind study lasted 24 weeks while patients face life-long challenges from XLH, with its report noting ‘uncertainty about the long-term efficacy and safety of burosumab.’

However, the research so far is promising, with placebo-controlled, randomised studies revealing a ‘normalisation’ of phosphate levels, and improved outcomes related to patients’ symptoms, including some improvement in bone health.

Burosumab works by intercepting an hormone growth factor that usually acts to lower the amount of phosphate in the blood. It targets this and prevents its usual process, working to increase the phosphate levels towards normal levels in the blood.

Jeremy Morgan, President of Kyowa Kirin International, said that extending access to the new drug to adults in Scotland will provide a “paradigm shift” in the management of XLH, adding:

“We are committed to working with the community to collect more data on the efficacy and tolerability of the treatment over the next few years.”

Oliver Gardiner, Founder and Trustee of XLH UK, said:

“I am delighted that adults with symptomatic XLH now have access to Crysvita in Scotland. Access to a treatment that can reduce some of the most burdensome symptoms of XLH, which is easily administered, will not only provide a vital step change in the management of this disease for adults, but also support greater independence.”