Ultragenyx's burosumab hits mark in Phase III XLH study

Ultragenyx Pharmaceutical Inc. (NASDAQ:RARE) added $11.37 (19%) to $71.45 in after-hours trading after it said burosumab (KRN23, UX023) significantly improved serum phosphorus levels in a Phase III trial to treat X-linked hypophosphatemia, meeting the study's primary endpoint. At week 24, 94% of patients receiving burosumab achieved and maintained levels above the lower limit of normal, compared with 8% for placebo (p<0.0001).

Ultragenyx and Kyowa Hakko Kirin Co. Ltd. (Tokyo:4151) share rights to burosumab, a recombinant human IgG1 mAb against fibroblast growth factor 23 (FGF23)...