Long-Term Treatment with Crysvita Reduces the Burden of Disease in Adults With XLH

Kyowa Kirin reported the publication of new data highlighting the sustained benefits of treatment with Crysvita in adults with X-linked hypophosphataemia, a rare genetic metabolic bone disease.

The data, published in the BMJ journal RMD Open, Rheumatic and Musculoskeletal Diseases, show that adults with XLH experience substantial pain, stiffness, fatigue and impairment in physical and ambulatory function. Treatment with Crysvita was associated with a significant improvement from baseline after 96 weeks.

“One of our areas of focus is to generate new data that improve our understanding of how best to manage and treat XLH,” said Tomohiro Sudo, executive officer, head of Global Product Strategy Department of Kyowa Kirin. “These important new data highlight the many physical challenges that people living with XLH face every day, how their needs could be better met and how Kyowa Kirin is delivering on its purpose, to make people smile.”

X-linked hypophosphataemia (XLH) is a rare, genetic disease that causes abnormalities in the bones, muscles, and joints. Though not life-threatening, its burden is life-long and progressive, and it may reduce a person’s quality of life. XLH is the most common form of hereditary rickets.  It can sometimes appear in individuals with no family history of the disease but is usually passed down from a parent who carries the defective gene.

People with XLH have a genetic defect on the X-chromosome, which causes an excessive loss of phosphate through the urine and poor absorption from the gut due to excess of a hormone known as fibroblast growth factor-23 (FGF23), resulting in chronically low levels of phosphate in the blood. Phosphate is a key mineral needed for maintaining the body’s energy levels, muscle function, and the formation of healthy bones and teeth. While there is no cure for XLH, therapies aimed at helping to restore and maintain phosphate to normal levels within the body may help to improve the progression of disease symptoms.

Created and developed by Kyowa Kirin, Crysvita (burosumab) is a recombinant fully human monoclonal IgG1 antibody against the phosphaturic hormone fibroblast growth factor 23 (FGF23), a hormone that reduces serum levels of phosphate by regulating phosphate excretion and active vitamin D production by the kidney. Kyowa Kirin and Ultragenyx Pharmaceutical have been collaborating in the development and commercialization of Crysvita globally, which has been approved since 20218 as a treatment for patients with XLH aged one year and older in the European Union, and for patients aged six months and older in the United States. It is also approved in Japan, Canada, and Switzerland.

The new data are from a randomized, double-blind, placebo-controlled, phase 3 study with an open-label extension to assess the efficacy and safety of Crysvita in adults with XLH. The study met its primary endpoint, showing a statistically significant effect in increasing serum phosphorus concentrations at 24 weeks, compared to placebo.3 After 24 weeks, all patients were switched to CRYSVITA treatment and data was collected on metabolic and biochemical markers, patient reported outcomes (PROs) and measures of mobility up to 96 weeks. This new publication focuses on the results from the PRO analysis and mobility scores.

At week 96, the study showed statistically significant improvements in PROs, including the Western Ontario and the McMaster Universities Osteoarthritis Index (WOMAC), Brief Pain Inventory–Short Form (BPI-SF) and Brief Fatigue Inventory (BFI), compared to baseline.1 Statistically significant improvements in ambulatory function, measured by the 6-minute walk test (6MWT), were also seen at 96 weeks compared to baseline. Data previously published at 48 weeks also showed improvements in some PROs, including stiffness and pain, as well as fracture healing.

“The study highlights the many physical challenges faced by adult patients with XLH, including pain, stiffness, fatigue and difficulty walking or physical function,” said lead author Karine Briot, Hôpital Cochin, Paris, France. “Burosumab treatment has previously been shown to improve phosphate homeostasis in adult XLH patients, compared to placebo. This new analysis suggests that, despite the long-term complications and physical impairment associated with XLH in adults, treatment with burosumab can also improve the physical function and quality of life of adults with XLH over the longer term.”

Photo: Karine Briot, Hôpital Cochin, Paris, France

Author: Rare Daily Staff