8. Crysvita

Ultragenyx logo
(Utragenyx)

Active ingredient: burosumab-twza 
Disease: X-linked hypophosphatemia
Peak sales estimate: $1 billion 
Approved: April 17 
Company: Ultragenyx

The scoop: Ultragenyx teamed up with Kyowa Kirin back in 2013 to develop the latter’s X-linked hypophosphatemia (XLH) drug for the U.S., Canadian and European markets. Five years later, after putting up impressive phase 3 data, Crysvita sailed past the FDA and became the first approved drug for XLH, a rare, inherited form of rickets. Like patients with rickets, most XLH patients have bent legs, bone pain and short stature. But unlike rickets patients, people with XLH cannot be treated with vitamin D therapy. Crysvita treats XLH by blocking the hormone fibroblast growth factor 23 (FGF23), which is overproduced in XLH patients due to mutations in the PHEX gene. Excess FGF23 causes patients to lose phosphate through their urine and renders them unable to produce vitamin D, making their bones soft and weak. “By targeting this mechanism Crysvita leads to sustained improvements in phosphate metabolism with concurrent repair of the skeleton, even after prior treatment with conventional approaches," said Tom Carpenter, M.D., a professor of pediatric endocrinology at Yale University and the lead study investigator. Ultragenyx will price the drug at $160,000 per year in children and $200,000 per year for adults after rebates and discounts, according to a note from Evercore ISI analyst Steve  Breazzano after Crysvita’s approval. — Amirah Al Idrus

8. Crysvita
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