Crysvita FDA approval for TIO : Ultragenyx Pharmaceutical and Kyowa Kirin have secured approval for their recombinant fully human monoclonal IgG1 antibody Crysvita (burosumab) from the US Food and Drug Administration (FDA) for the treatment of tumor-induced osteomalacia (TIO).

The FDA approval of Crysvita is for the treatment of fibroblast growth factor 23 (FGF23)-related hypophosphatemia in tumor-induced osteomalacia associated with phosphaturic mesenchymal tumors that cannot be resected curatively or localized in adults and pediatric patients aged two years and older.

According to the FDA, tumor-induced osteomalacia is a rare disease that is associated with the development of tumors that cause weakened and softened bones. The tumors associated with the rare disease release a peptide hormone-like substance called fibroblast growth factor 23 (FGF23) that reduces phosphate levels.

Crysvita is now the first therapy for tumor-induced osteomalacia to have been approved in the US. The human antibody has been designed to prevent the excess activity of FGF23, which also curbs active vitamin D production by the kidney.

Prior to bagging this approval, in  April 2018, Crysvita was given the nod by the FDA for the treatment of X-linked hypophosphatemia (XLH) in adult and pediatric patients, aged one year and older. The XLH indication was expanded last September to include infants as young as six months old.

Commenting on Crysvita FDA approval for TIO, Theresa E. Kehoe – acting director of the Division of General Endocrinology in the FDA’s Center for Drug Evaluation and Research, said: “Treatment for TIO focuses on identifying and removing the tumor that causes the disease. However, when that is not possible, Crysvita can help increase the levels of phosphate in the blood.

“As the first FDA-approved therapy to treat this debilitating disease, today’s action is an important step in finding treatment options for patients living with TIO whose tumor cannot be found or removed.”

Crysvita FDA approval for TIO was driven by the findings of a couple of single-arm phase 2 studies in 14 adult patients that were held by Ultragenyx Pharmaceutical in the US and a study in 13 adult patients carried out by Kyowa Kirin in Japan and South Korea. In the two studies, Crysvita was associated with surges in serum phosphorus and serum 1,25-dihydroxyvitamin D levels.

Camille L. Bedrosian – Chief Medical Officer of Ultragenyx Pharmaceutical, commenting on Crysvita FDA approval for TIO, said: “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.

“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.”

Crysvita was discovered by Kyowa Kirin. The Japanese pharma company had entered into a collaboration and licensing agreement for the human antibody’s global development and commercialization with the US-based Ultragenyx Pharmaceutical.

  burosumab, Camille L. Bedrosian, Crysvita, Kyowa Kirin, osteomalacia, Theresa E. Kehoe, tumor-induced osteomalacia, Ultragenyx Pharmaceutical, US Food and Drug Administration, USA