Kyowa Kirin has received approval from the US Food and Drug Administration (FDA) for a dosing update to the prescribing information for Crysvita (burosumab-twza), introducing a new option for adults with X-linked hypophosphataemia (XLH).
Affecting adults and children, this rare, progressive, genetic disorder impacts both bone and muscle health due to the body’s inability to retain sufficient phosphorus, a mineral essential for bone health.
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Following the update, healthcare providers can increase both the dose and frequency of the therapy for XLH patients whose serum phosphorus remains below normal after the initial treatment.
Patients can transition to a 0.5mg/kg dose, not exceeding 90mg, every two weeks. Should further adjustment be required after four weeks of this regimen, the dose can be raised to 1mg/kg every two weeks, still not exceeding 90mg.
Discovered by Kyowa Kirin, Crysvita is a recombinant, fully human monoclonal immunoglobulin G1 (IgG1) antibody that targets fibroblast growth factor 23 (FGF23), the underlying cause of hypophosphataemia in XLH.
By inhibiting FGF23, Crysvita helps restore renal phosphorus reabsorption and increases serum concentrations of active vitamin D.
The product is approved in the US for the treatment of XLH in adults and children aged six months and older.
Kyowa Kirin senior vice-president and rare disease franchise head Richard Wilson said: “Kyowa Kirin is committed to delivering solutions that make a meaningful difference for people living with XLH.
“As the only FDA-approved treatment for XLH, Crysvita plays a critical role in care, and it’s essential that clinicians have the flexibility to support optimal patient outcomes.
“While most adults with XLH maintain normal serum phosphorus levels with Crysvita administered every four weeks, this update enables a more personalised approach for those who need additional support to reach and maintain serum phosphorus levels within normal range.”
In October 2025, Japan’s Ministry of Health, Labor and Welfare (MHLW) granted orphan regenerative medicine product designation to Kyowa Kirin and Orchard Therapeutics’ ex vivo autologous haematopoietic stem cell (HSC) gene therapy, OTL-200, for metachromatic leukodystrophy (MLD).
