Kyowa Kirin's Drug Crysvita Poses Risk of Severe Hypercalcemia

Kyowa Kirin GmbH has issued a "Red Hand Letter" (Rote-Hand-Brief), in coordination with the EMA and the Paul-Ehrlich-Institut (PEI), to inform healthcare professionals about the risk of elevated serum calcium, including severe hypercalcemia, and/or parathyroid hormone in patients treated with Crysvita (burosumab) injection solution.

Crysvita is a recombinant human monoclonal antibody indicated for the treatment of X-linked hypophosphatemia in adults and in children/adolescents aged 1 to 17 years with radiologically confirmed bone disease. It is also used for FGF23-related hypophosphatemia in tumor-induced osteomalacia associated with phosphaturic mesenchymal tumors that cannot be cured by resection or localized.

The manufacturer recommends that Crysvita should not be administered to patients with moderate to severe hypercalcemia (serum calcium > 3.0 mmol/l) until the hypercalcemia is adequately treated and resolved. To prevent the occurrence of severe hypercalcemia in at-risk patients, monitoring of serum calcium and parathyroid hormone levels before and during treatment is advised. Serum calcium should be measured one to two weeks after initiation and after dose adjustments; calcium and parathyroid hormone levels should be determined every six months (every three months for children aged one to two years).

Additional risk factors such as hyperparathyroidism, prolonged immobilization, dehydration, hypervitaminosis D, or impaired renal function should also be considered and managed appropriately, as they can further increase the risk of hypercalcemia. The product information will be updated to reflect this risk. Healthcare professionals are urged to consult the full "Red Hand Letter" for detailed guidance.