FDA Expands Use of Crysvita to Include Treatment of X-Linked Hypophsphatemia

September 30, 2019

The U.S. Food and Drug Administration has approved a label expansion for Crysvita to include new clinical data demonstrating its superiority as a treatment versus oral phosphate and active vitamin D, the conventional therapy for pediatric patients with X-linked hypophosphatemia (XLH).

The label expansion also includes the improvement in stiffness and maintenance of efficacy of Crysvita in adult patients with longer-term treatment, as well as the expansion of the indication to include infants as young as six months of age.

XLH is a rare, hereditary, progressive, and lifelong skeletal disorder characterized by renal phosphate wasting caused by excess production of phosphaturic hormone fibroblast growth factor 23 (FGF23). FGF23 is a hormone that reduces serum levels of phosphorus and active vitamin D by regulating phosphate excretion and active vitamin D production by the kidney. It affects both children and adults. In children, XLH causes rickets that leads to lower-extremity deformity, delayed growth, and decreased height. Adults with XLH have an increased risk of fractures.

Crysvita (burosumab) is a recombinant fully human monoclonal IgG1 antibody that binds to and inhibits the biological activity of FGF23, restoring renal phosphate reabsorption and increasing the serum concentration of 1,25 dihydroxy vitamin D. By blocking excess FGF23 in patients, Crysvita is intended to increase phosphate reabsorption from the kidney and increase the production of vitamin D, which enhances intestinal absorption of phosphate and calcium.

Crysvita was discovered by Kyowa Kirin and developed and commercialized through a collaboration and licensing agreement with Ultragenyx. It was first approved in the United States in April 2018 for the treatment of XLH in adult and pediatric patients one year of age and older.

“We are pleased that the updated Crysvita label includes compelling results from a controlled clinical trial demonstrating that Crysvita is significantly more effective than conventional therapy in normalizing phosphorus levels, reducing rickets and lower leg deformity, and improving growth in children with XLH. Furthermore, longer-term data from a study in adults are included showing important sustained Crysvita efficacy in this life-long disease,” said Camille Bedrosian, chief medical officer of Ultragenyx. “As part of our commitment to support the XLH community, we worked closely with the FDA to update the prescribing information for Crysvita so physicians could make more informed treatment decisions for their patients with XLH and ensure that younger patients could be treated as this disease is present at birth.”

Photo: Camille Bedrosian, chief medical officer of Ultragenyx

Author: Rare Daily Staff

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