In February 2018, Burosumab (Crysvita®), developed by Kyowa Hakko Kirin Co., Ltd. and Ultragenyx Pharmaceutical Inc.), received its first global approval in the EU, Norway, Iceland and Liechtenstein for the treatment of X-linked hypophosphataemia (XLH) with radiographic evidence of bone disease in children one year of age and older and adolescents with growing skeletons. This is a conditional marketing authorisation and requires completion of on-going paediatric clinical trials. The agent was subsequently approved by the US FDA in April 2018, for this rare form of inherited rickets, for which vitamin D therapy is ineffective.
Burosomab is a recombinant human IgG1 antibody that inhibits fibroblast growth factor 23 (FGF23). It is administered as a subcutaneous injection and increases the tubular reabsorption of phosphate from the kidneys resulting in an increase in serum concentration of 1,25-dihydroxyvitamin D.
While this is the most common form of hereditary hypophosphatemia, it is still a rare childhood-onset disease with a prevalence of 1 in 20,000 people.
Emil D Kakkis, MD, PhD, Chief Executive Officer and President of Ultragenyx, described the disease as “extremely debilitating”, and Dr. Tom Stratford, President and Chief Executive Officer of Kyowa Kirin International, explained that the company “will now focus [its] efforts on working with health authorities to ensure patient access in European countries…[and will continue] to further develop [its] understanding of the real-world experience of people affected by XLH. This will help to ensure appropriate patient identification and diagnosis and improve standards of care for this rare condition.”
Burosumab has been awarded Orphan Drug Status by both the EMA and the US FDA; in the US it has been designated as Breakthrough Therapy and granted Priority Review status and additionally the sponsor is receiving a Rare Pediatric Disease Priority Review Voucher.
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