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# Ultragenyx NDA Approved for Rare Form of Rickets
- URL: https://www.fdaweb.com/ultragenyx-nda-approved-for-rare-form-of-rickets/
- Published: 2018-04-17T12:00:00.000Z
- Updated: 2026-09-14T23:59:20.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5141243

FDA has approved an Ultragenyx Pharmaceutical NDA for Crysvita (burosumab), the first drug approved to treat adults and children ages one year and older with x-linked hypophosphatemia. The rare, inherited form of rickets causes low levels of phosphorus in the blood, and it leads to impaired bone growth and development, according to an [agency notice](https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm604810.htm?ref=fdaweb.com).

Approval was based on data from four clinical trials, including a placebo-controlled trial where 94% of adults receiving Crysvita once a month achieved normal phosphorus levels compared to 8% for those on placebo. In children, 94% to 100% treated with the therapy every two weeks achieved normal phosphorus levels. “The most common adverse reactions in adults taking Crysvita were back pain, headache, restless leg syndrome, decreased vitamin D, dizziness and constipation,” the notice says. “The most common adverse reactions in children were headache, injection site reaction, vomiting, decreased vitamin D and pyrexia (fever).”

The approval also provides the company with a The sponsor is receiving a rare pediatric disease priority review voucher for use with a separate submission at a later date.