- Burosumab is a monoclonal antibody that acts against the fibroblast growth factor 23 (FGF23)
- It has been granted conditional approval for the treatment of X-linked hypophosphatemia from the European Union
- Further studies are required before its use can be established for the condition
The European Medicines Agency's (EMA) Committee for Medicinal Products for Human Use (CHMP) has granted conditional marketing authorization for burosumab for the treatment of a rare bone disease called X-linked hypophosphatemia (XLH). Burosumab can now be used in the European Union in children over 1 year of age and in adolescents with growing skeletons and with radiological evidence of the presence of the condition. Currently, the US Food and Drug Administration (FDA) is also reviewing the drug for its use in the rare condition.
Burosumab is a monoclonal antibody directed against the hormone fibroblast growth factor 23 (FGF23). FGF23 prevents the reabsorption of phosphate by the kidney. It also plays a role in the regulation of vitamin D. An excess of FGF23 results in excess loss of phosphate and reduces its blood level. Burosumab increases the reabsorption of phosphate from the kidney thereby increasing the blood phosphate levels. It also increases the production of vitamin D, which in turn increases the absorption of calcium and phosphate from the intestine, thereby increasing their blood levels.
Burosumab is also being evaluated for the treatment of tumor-induced osteomalacia, another condition that weakens bones. Tumor-induced osteomalacia occurs in patients with benign tumors and is associated with high FGF23 levels.
About X-linked Hypophosphatemia (XLH)X-linked hypophosphatemia (XLH) is a rare inherited bone disorder that arises due loss of excess phosphate through the urine. This results in low levels of phosphate in the blood, which in turn draws phosphate from the bone, thereby weakening it and resulting in rickets. The patient has a high level of the FGF23 hormone.
Children with XLH suffer from bone and teeth pain, along with bone deformities that include bent legs and short stature. Other features include a waddling gait, muscle weakness, pseudofractures, narrowing of the spinal cord, abnormal bone growth at the attachment of tendons or ligaments to bone (enthesopathy) and osteoarthritis. Treatment includes the intake of oral phosphate and vitamin D, which treat the symptoms but do not address the underlying problem.