Searchable abstracts of presentations at key conferences on calcified tissues
Bone Abstracts (2019) 7 P72 | DOI: 10.1530/boneabs.7.P72

1Alder Hey Children’s Hospital, Liverpool, UK; 2Bristol Royal Hospital for Children, Bristol, UK; 3Evelina Children’s Hospital, London, UK; 4Royal Manchester Children’s Hospital, Manchester, UK; 5Birmingham Children’s Hospital, Birmingham, UK; 6Nottingham Children’s Hospital, Nottingham, UK; 7Leeds Teaching Hospital, Leeds, UK; 8Royal Hospital for Sick Children, Edinburgh, UK; 9Southampton University Hospital, Southampton, UK; 10Sheffield Children’s Foundation Trust, Sheffield, UK; 11MAP BioPharma, Papworth Everard, Cambridge, UK; 12Kyowa Kirin, Galashiels, UK.

Objectives: X-linked hypophosphataemia (XLH) is a rare inherited form of osteomalacia characterised by low blood phosphate levels which lead to inadequate mineralisation of bone and rickets. Burosumab is an anti-FGF23 fully human monoclonal-antibody, and the first treatment to target the underlying pathophysiology of XLH. Real-world evidence is important in validating the findings of clinical studies. We report relevant real-world biochemical data on children under five years old for the first 6 months of burosumab treatment.

Methods: An early access program (EAP) for burosumab was made available for children in the United Kingdom with XLH in 12 specialist centres. Inclusion criteria for the EAP included radiographic evidence of disease, XLH confirmed by genetic PHEX mutation or familial X-linked inheritance of mutation or family history. Patients must have also had an unsatisfactory response to best available care and treatment. EAP enrolment was between January and March 2018. A total of 142 applications were received of which 135 were approved with 132 receiving treatment (dose in accordance with EMA marketing authorisation).

Results: Data are available on 10 children under five years (mean age 2.8 years; 1.6–4 years) who have completed a median of 6 months (20–26 weeks) of burosumab treatment. Mean dose administered by subcutaneous injection was 0.81 mg/kg (0.55–1.01 mg/kg) at week 0 and 1.09 mg/kg (0.57–2.01 mg/kg) at the end of the 20–26 week period. Mean fasting serum phosphorus was 0.73 mmol/l (0.6–0.83 mmol/l) in week 0 rising to 1.02 mmol/l (0.82–1.3 mmol/l) at week 20–26 representing a 40% increase in serum phosphate levels. Mean serum ALP fell from 808.2 IU/l (297–2124 IU/l) at week 0 to 612 IU/l (291–1459 IU/l) at week 20–26, representing a 24% decrease in ALP. No patients discontinued treatment due to adverse events.

Conclusions: Early data from treating young children with XLH with burosumab in a real-world UK setting demonstrate that key biochemical responses are aligned with findings from the clinical study program. This provides reassurance that the improvement in key biochemical parameters is consistent across all ages within its licensed indication.

Disclosure: The authors declared no competing interests.

Volume 7

9th International Conference on Children's Bone Health


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