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# sBLA for Crysvita Approved for Expanded Use
- URL: https://www.fdaweb.com/sbla-for-crysvita-approved-for-expanded-use/
- Published: 2020-06-18T12:00:00.000Z
- Updated: 2026-09-14T16:18:45.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5147042

FDA has approved an Ultragenyx Pharmaceutical and Kyowa Kirin supplemental BLA for Crysvita (burosumab) for treating fibroblast growth factor 23 (FGF23)-related hypophosphatemia in tumor-induced osteomalacia (TIO) associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized in adults and pediatric patients two years of age and older. The companies say that Crysvita is a human antibody that blocks excess activity of FGF23, a hormone that causes phosphate urinary excretion and suppresses active vitamin D production by the kidney.

TIO is described as a rare disease caused by typically benign, slow-growing tumors that produce excess levels of FGF23, which is involved in phosphate reabsorption. “Patients with TIO can experience symptoms including severe hypophosphatemia (low levels of phosphate in the blood), osteomalacia (softening of the bones), muscle weakness, fatigue, bone pain and fractures,” the companies say.

Approval was based on data from two single-arm Phase 2 studies, a 144-week study in 14 adult patients conducted by Ultragenyx in the U.S., and an 88-week study in 13 adult patients conducted by Kyowa Kirin in Japan and South Korea. “In both studies, Crysvita was associated with increases in serum phosphorus and serum 1,25-dihydroxyvitamin D levels,” the companies say, adding that increased phosphate levels led to improvements in osteomalacia.

Crysvita was originally approved 4/2018 for treating X-linked hypophosphatemia in adult and pediatric patients one year of age and older. That indication was expanded in 9/2019 to include infants as young as six months.