Kyowa Hakko Kirin Co., Ltd. announced KRN23, an investigational recombinant fully human monoclonal IgG1 antibody against the phosphaturic hormone fibroblast growth factor 23(FGF23), has received Breakthrough Therapy Designation from the U.S. Food and Drug Administration (FDA) for the treatment of X-linked hypophosphatemia (XLH) in pediatric patients one year of age and older. Kyowa Hakko Kirin and Ultragenyx entered into a collaboration and license agreement in August 2013 to develop and commercialize KRN23.