FDA Approves Crysvita (burosumab) for X-Linked Hypophosphatemia and Tumor-Induced Osteomalacia
The FDA has approved Crysvita (burosumab) for the treatment of X-linked hypophosphatemia (XLH) in adult and pediatric patients 6 months of age and older, and for FGF23-related hypophosphatemia in tumor-induced osteomalacia (TIO) associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized in patients 2 years and older. Crysvita is a fibroblast growth factor 23 (FGF23) blocking antibody, the first therapy targeting the underlying cause of these rare phosphate-wasting disorders. The approval provides a new option for patients who previously relied on oral phosphate and active vitamin D analogs, which require discontinuation one week before starting Crysvita. Clinicians should note that fasting serum phosphorus must be below the reference range for age prior to initiation, and dose adjustments are guided by serum phosphorus levels to avoid hyperphosphatemia.
＋ Clinical Details (Mechanism · Dosing · Trial Data · Warnings)
Crysvita is a fibroblast growth factor 23 (FGF23) blocking antibody. It binds to and inhibits FGF23, thereby increasing renal phosphate reabsorption and serum phosphorus levels.
Crysvita is indicated for the treatment of X-linked hypophosphatemia (XLH) in adult and pediatric patients 6 months of age and older. It is also indicated for the treatment of FGF23-related hypophosphatemia in tumor-induced osteomalacia (TIO) associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized in adult and pediatric patients 2 years of age and older.
Crysvita is for subcutaneous use only. Prior to starting, discontinue oral phosphate and active vitamin D analogs for one week. Fasting serum phosphorus must be below the reference range for age. For pediatric XLH (6 months and older): patients <10 kg start at 1 mg/kg every 2 weeks; patients ≥10 kg start at 0.8 mg/kg (min 10 mg, max 90 mg) every 2 weeks. Dose may be increased up to 2 mg/kg (max 90 mg) every 2 weeks. For adult XLH: 1 mg/kg (max 90 mg) every 4 weeks. For pediatric TIO (2 years and older): start 0.4 mg/kg every 2 weeks, may increase up to 2 mg/kg (max 180 mg) every 2 weeks. For adult TIO: start 0.5 mg/kg every 4 weeks, may increase up to 2 mg/kg (max 180 mg) every 2 weeks. Maximum volume per injection is 1.5 mL.
Trial data not available in label.
Contraindicated in patients with severe renal impairment or end-stage renal disease. Prior to starting, discontinue oral phosphate and active vitamin D analogs. Monitor serum phosphorus and adjust dose to avoid hyperphosphatemia. In patients at high risk for hypercalcemia, assess serum calcium and parathyroid hormone levels before starting.
Crysvita is a targeted therapy for XLH and TIO, addressing the underlying FGF23 excess. It is indicated after discontinuation of conventional therapy (oral phosphate and active vitamin D analogs). Dosing is individualized based on weight and serum phosphorus levels.
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