Ultragenyx Pharmaceutical Inc. is a clinical-stage biopharmaceutical company. The Company is focused on the identification, acquisition, development, and commercialization of products for the treatment of genetic diseases. Its clinical-stage pipeline consists of two product categories: biologics (including a monoclonal antibody and an enzyme replacement therapy), and small-molecule substrate replacement therapies. Its product candidates under biologics category include KRN23 (UX023) and recombinant human beta-glucuronidase (rhGUS) (UX003). Its product candidates under small-molecule category include UX007 and aceneuramic acid extended-release (Ace-ER) (UX001). It is also developing recombinant human protective protein cathepsin-A (rhPPCA). KRN23 is a fully human monoclonal antibody. rhGUS is an intravenous (IV) enzyme replacement therapy. UX007 is a substrate replacement therapy. It is developing Ace-ER for the treatment of GNE myopathy. rhPPCA is in preclinical development.