X-linked hypophosphatemia (XLH) rare genetic disorder due by inactivating mutations in the
PHEX gene leading to increased levels in FGF-23. Elevated FGF-23 reduces renal phosphate
reabsorbtion and and limits 1-alpha hydroxylase driven Vitamin D activation, eventually
leading to phosphate wasting, defective bone mineralization and additional health issues.
Burosumab is a recombinant fully human IgG1 monoclonal antibody developed to treat XLH by
binding FGF23, thereby restoring normal phosphate homeostasis.
BUR03 is a Phase 3b open-label, single-arm, single-center study to confirm the efficacy and
safety of Burosumab treatment in adult (age ≥18 years) XLH patients without upper age limit
and irrespective of baseline pain level and to further evaluate the efficacy in this cohort
and the assocaited effect of treatment on physical functioning, mobility and activity.
The study aims at enrolling and treating 34 subjects with a confirmed diagnosis of XLH with
q4w s.c. injection of Burosumab 1mg/kg body weight over 48 weeks.
Primary objective is to attiain normal serum phosphorus levels, secondary objectives include
key parameters of physical function and activity, mobility and mineral homeostasis.