Burosumab

How it works

It binds and inhibits fibroblast growth factor 23 (FGF23), restoring renal phosphate reabsorption and increasing serum phosphate and active vitamin D concentrations.

Prescribing in practice

• Oral phosphate and active vitamin D analogues must be stopped before starting to avoid hyperphosphataemia and the risk of nephrocalcinosis.
• It is a specialist-initiated subcutaneous therapy with administration and dose titration guided by serum phosphate.
• Injection-site reactions and hypersensitivity can occur, so administration should follow the SPC closely.

Monitoring

Monitor fasting serum phosphate regularly during titration, together with renal function and assessment for nephrocalcinosis.

Counselling the patient

• Stop any conventional phosphate or vitamin D supplements before treatment unless told otherwise.
• Report skin reactions at the injection site or signs of an allergic reaction.
• Attend for regular blood tests so the dose can be adjusted safely.

Evidence & guidelines

NICE has appraised burosumab for X-linked hypophosphataemia; prescribing should follow the approved indication and the SPC.