FDA approves Crysvita for the treatment of fibroblast growth factor 23 -related hypophosphatemia in tumor-induced osteomalacia (TIO) Ultragenyx + Kyowa Kirin Co., Ltd.

Ultragenyx Pharmaceutical Inc.and Kyowa Kirin Co., Ltd. announced that the FDA has approved Crysvita (burosumab) for the treatment of 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 2 years of age and older.

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.“For approximately half of all individuals with TIO, surgical removal of the tumors is not possible, leaving these patients with no other treatment options. The FDA approval of Crysvita marks the first treatment option that addresses the cause of the severe hypophosphatemia and osteomalacia resulting from these rare tumors,” said Camille L. Bedrosian, M.D., Chief Medical Officer of Ultragenyx. “We plan to leverage our experience and existing infrastructure with Crysvita in X-linked hypophosphatemia to bring this important medicine to patients living with the rare, painful and debilitating disorder of TIO.”.

TIO (tumor-induced osteomalacia) is 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. There are an estimated 500 to 1,000 people in the United States with TIO, and approximately half of all cases are believed to be inoperable. In patients for whom the tumor or lesion is inoperable, the current treatment consists of oral phosphate and/or active vitamin D replacement. Efficacy of this management is often limited, and its benefits must be balanced with monitoring for potential risks.

This is the second FDA-approved indication for Crysvita, which was first approved in April 2018 for the treatment of X-linked hypophosphatemia (XLH) in adult and pediatric patients one year of age and older. The XLH indication was expanded in September 2019 to include infants as young as six months of age..