Burosumab
Burosumab, sold under the brand name Crysvita, is a human monoclonal antibody medication for the treatment of X-linked hypophosphatemia and tumor-induced osteomalacia. Burosumab was approved by the FDA for its intended purpose, in patients aged one year and older, in April 2018. The FDA approval fell under both the breakthrough therapy and orphan drug designations. It was approved for use in the European Union in February 2018.The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication.

Medical uses
In the United States, burosumab is indicated for the treatment of adults and children ages one year and older with x-linked hypophosphatemia (XLH), a rare, inherited form of rickets, and for the treatment of people age two and older with tumor-induced osteomalacia (TIO), a rare disease that is characterized by the development of tumors that cause weakened and softened bones. The tumors associated with TIO release a peptide hormone-like substance known as fibroblast growth factor 23 (FGF23) that lowers phosphate levels.In the European Union, burosumab is indicated for the treatment of X-linked hypophosphataemia with radiographic evidence of bone disease in children one year of age and older and adolescents with growing skeletons.XLH is genetic disorder affecting phosphate metabolism within the body, which results in hypophosphatemia. The disease is characterized by overproduction of the FGF23 hormone in bone cells. The FGF23 hormone is responsible for blocking phosphate re-absorption by the kidney and the suppression of the vitamin D dependent phosphate absorption by the intestine. Due to the excess activity of FGF23, phosphate levels in the blood are abnormally low, which affects the constitution of bone. Thus, burosumab is designed to bind to the FGF23 receptor and inhibit the excess activity of the FGF23 hormone within the body.While burosumab is effective for the treatment of X-linked hypophosphatemia, the National Institute for Health and Care Excellence in England and Wales initially raised concerns regarding the incremental cost-effectiveness of the new treatment but the drug is available through a simple discount scheme.

History
This drug was developed by Ultragenyx and is in a collaborative license agreement with Kyowa Hakko Kirin.

References
External links
"Burosumab". Drug Information Portal. U.S. National Library of Medicine.