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Laboratory Medicine
FDA approves first therapy for rare inherited form of rickets

Written by Rusa Tskitishvili

 

The US FDA has approved the orphan drug burosumab (Crysvita, Ultragenyx Pharmaceutical Inc) to treat adults and children age 1 year and older with X-linked hypophosphatemia (XLH), a rare, inherited, progressive form of rickets.

XLH is characterized by renal phosphate wasting caused by excess fibroblast growth factor 23 (FGF23) production. Burosumab  is designed to bind the excess FGF23 in patients with XLH, thereby normalizing phosphorus levels, improving bone mineralization, improving rickets in children, and healing fractures in adults.

In a placebo-controlled trial, 94% of adults receiving burosumab once a month achieved normal phosphorus levels compared with 8% of those receiving placebo. In children, 94% to 100% of patients treated with burosumab every 2 weeks achieved normal phosphorus levels. In both children and adults, radiograph findings associated with XLH improved with burosumab treatment.

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