On Jun. 18, 2020, the U.S. Food and Drug Administration (FDA) approved Ultragenyx Pharmaceutical ‘s Crysvita (burosumab-twza) injection to treat patients age two and older with tumor-induced osteomalacia (TIO), a rare disease that is characterized by the development of tumors that cause weakened and softened bones.

The tumors associated with TIO release a peptide hormone-like substance known as fibroblast growth factor 23 (FGF23) that lowers phosphate levels.