Ultragenyx Pharmaceutical Inc., of Novato, Calif., dosed the first patient in a phase II study of recombinant human beta-glucuronidase (rhGUS, UX003) in patients younger than 5 years with mucopolysaccharidosis 7 (MPS 7, or Sly syndrome), potentially including patients with non-immune hydrops fetalis, a severe infantile presentation of the disease.