Burosumab (Crysvita®), a fully human
IgG1 monoclonal antibody directed at
fibroblast growth factor 23 (FGF23), is indicated for the treatment of
X-linked hypophosphatemia (XLH), a condition associated with excessive FGF23 production. It directly addresses the excessive FGF23 activity in patients with XLH by binding to FGF23, and inhibiting its signaling. This leads to increased gastrointestinal
phosphate absorption and renal
phosphate reabsorption, thereby improving serum
phosphate levels, and, ultimately, bone mineralization and the risk of
bone disease. In clinical trials, subcutaneous
burosumab increased serum
phosphorus levels in pediatric and adult patients with XLH, as well as significantly improving the severity of
rickets in children, and improving
pain, stiffness, physical functioning, and fracture/pseudofracture healing in adults.
Burosumab is well tolerated by children and adults with XLH, with most treatment-emergent adverse events being of mild to moderate severity.