Burosumab for treating X-linked hypophosphataemia in children and young people

Burosumab (Crysvita, Kyowa Kirin) is monoclonal antibody that binds to and inhibits the activity of fibroblast growth factor 23 (FGF23). By inhibiting FGF23, burosumab is expected to increase reabsorption of phosphate from the kidney and, through vitamin D production, improve intestinal absorption of calcium and phosphate. For this appraisal, burosumab had a conditional marketing authorisation for 'the treatment of X‑linked hypophosphataemia with radiographic evidence of bone disease in children 1 year of age and older and adolescents with growing skeletons'. In October 2022, this was updated to a full marketing authorisation, in which burosumab is licensed 'for the treatment of X‑linked hypophosphataemia, in children and adolescents aged 1 to 17 years with radiographic evidence of bone disease, and in adults'.

Burosumab is administered via subcutaneous injection once every 2 weeks. The recommended starting dose is 0.4 mg/kg, the normal maintenance dose is 0.8 mg/kg and the maximum dose is 2 mg/kg up to 90 mg. Doses should be rounded to the nearest 10 mg. Treatment can begin in children aged 1 year and can continue until the bones stop growing.

The adverse reactions listed as very common (that is, occurring in 1 in 10 people or more) in the summary of product characteristics for burosumab include: injection site reactions, headache, pain in the extremities, decreased vitamin D, rash, toothache, tooth abscesses, myalgia and dizziness. For full details of adverse reactions and contraindications, see the summary of product characteristics.

The list price of burosumab in England is £2,992 (excluding VAT) per 10 mg vial (company submission). The company has a commercial arrangement. This makes burosumab available to the NHS with a discount. The size of the discount is commercial in confidence. It is the company's responsibility to let relevant NHS organisations know details of the discount.