The FDA is slated to announce its decision on Ultragenyx Pharmaceutical Inc.’s (RARE) Burosumab, proposed for the treatment of pediatric and adult patients with X-Linked Hypophosphatemia, on April 17, 2018.Being designated as a drug for a "rare pediatric disease", Burosumab if approved will fetch the Company a priority review voucher. The voucher can be redeemed by Ultragenyx to receive a priority review of a subsequent marketing application for a different product.RARE closed Tuesday’s (Mar.27) trading at $49.41, down 5.34%.