Last reviewed 2026-04-20 · How we verify

Crysvita (BUROSUMAB)

Burosumab-twza binds to and inhibits FGF23, restoring renal phosphate reabsorption and increasing 1,25 dihydroxy vitamin D levels.

Crysvita (Burosumab) is a small molecule modality developed by Ultragenyx Pharmaceuticals for the treatment of Familial X-linked Hypophosphatemic Vitamin D Refractory Rickets and Osteomalacia. It targets fibroblast growth factor 23, a protein involved in phosphate regulation. Crysvita was FDA-approved in 2018 and remains a patented product. Key safety considerations include monitoring of serum phosphate levels and potential effects on kidney function. It is a relatively new treatment option for these rare conditions.

At a glance

Mechanism of action

X-linked hypophosphatemia results from excessive FGF23, which reduces phosphate reabsorption in the kidneys and decreases 1,25 dihydroxy vitamin D production. Burosumab-twza targets and neutralizes FGF23, thereby improving phosphate reabsorption and boosting 1,25 dihydroxy vitamin D levels.

Approved indications

• Familial x-linked hypophosphatemic vitamin D refractory rickets
• Osteomalacia

Common side effects

• Pyrexia
• Injection site reaction
• Cough
• Vomiting
• Pain in extremity
• Headache
• Tooth abscess
• Dental caries
• Diarrhea
• Vitamin decreased
• Rash
• Toothache

Key clinical trials

• X-linked Hypophosphatemia Disease Monitoring Program
• Burosumab and 1-25 (OH) Vitamin D on Human Osteoblasts
• Burosumab for Fibroblast Growth Factor-23 Mediated Hypophosphatemia in Fibrous Dysplasia (PHASE2)
• Tumor-induced Osteomalacia Disease Monitoring Program
• Effective Dosing of Burosumab in XLH
• Post Marketing Surveillance Study to Observe Safety and Effectiveness of CRYSVITA® in S. Korean Patients
• Expanded Access to Burosumab
• Study to Assess the Safety, Tolerability, Pharmacokinetics and Efficacy of Burosumab in Patients Less Than 1 Year of Age (PHASE1,PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.