The Drug Burosumab Demonstrates Long-Term Benefits for X-Linked Hypophosphatemia

According to a story from Medscape, the drug burosumab (marketed as Crysvita) demonstrated its ability to provide long term benefits for nearly two years to patients with the rare disease X-linked hypophospatemia while maintaining a suitable safety profile. This drug was first approved in this indication in April 2018, but the results of this trial were the first to confirm the therapy’s long-term capabilities for the treatment of the illness.

About X-Linked Hypophosphatemia

X-linked hypophosphatemia (XLH) is a genetic disorder. It is considered a type of rickets that is distinguished from other types because vitamin D cannot cure it. Rickets is characterized by the abnormal softening of bones which can result in a bow-legged appearance and stance. The disorder is linked to mutations affecting the PHEX gene sequence found on the X chromosome. Symptoms of X-linked hypophosphatemia include soft bones, bone pain, osteoarthritis, teeth problems, and hearing loss. Treatment may include burosumab (as of 2018), calcitriol, phosphate, human growth hormone (HGH), and surgery to correct bowed legs or other bone deformities. The prevalence of this disease is about one in every 20,000 people. Inheritance of the condition is X-linked dominant, which means that men are more likely to express symptoms. To learn more about X-linked hypophosphatemia, click here.

Lifelong Treatment is Essential

The drug was able to demonstrate significant improvements in both physical function and the stiffness of bones. However, some patients still had difficulty with chronic pain. The reality is that patients with this disorder will need to take treatments for life. While the results of this trial are certainly a step forward, the impacts of burosumab after ten years or even several decades of use remain unclear. Nevertheless, the drug represents a significant improvement over other treatment options in terms of side effects, treatment burden, and quality of life. The main limitation of burosumab is its significant cost of around $200,000 per year.

About The Study

The trial included 134 adult patients who were given either placebo or a 1 mg/kg dose of the drug every four weeks for a 24 week period. This was expanded into an open-label extension period that was completed at the end of 48 weeks. The final extension period finished at 96 weeks. All patients treated saw their phosphorus levels drop into the normal range. The majority of patients (99 percent) all experienced some adverse effects from the treatment, such as injection site reactions, pain, and nasopharyngitis.


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