Bone Abstracts

Objectives: Burosumab, a monoclonal antibody that therapeutically targets the underlying elevated levels of fibroblast growth factor 23 (FGF23) in X-linked hypophosphatemia (XLH), is now available to children out of trial conditions. Our objective was to describe the effect of burosumab on quality of life, functionality and pain in a clinical setting.

Methods: Questionnaire tools were completed at baseline, 6 and 9 months for 9 children with XLH starting burosumab at Evelina London Children’s Hospital. Questionnaire tools used included: Core Paediatric Quality of Life Inventory (PedsQL Core), Paediatric Quality of Life multidimensional fatigue scale (PedsQL Fatigue), and Pain Severity Score (PSS) from the Brief Pain Index (BPI). 6-minute walk test (6MWT) and Movement ABC assessments were completed at baseline and 6 months to assess motor function and balance.

Results: Pain: There was an average increase in pain at 6 months which decreased to below baseline by 9 months. Mean PSS (N=8) was 2.13 (range 0–2.8) at baseline, 2.31 (range 0–6.75) at six months and 0.68 (range 0–2.25) at 9 months (maximum score 10). 2 patients reported no significant pain at baseline which remained unchanged. The increase of PSS at six months was only reported in 37.5% (N=3) patients. Fatigue: Patients felt less fatigued at 6 and 9 months compared to baseline, with Mean±S.D. PEDsQL Fatigue scores improving from 62.9±23.4 (N=6) to 74.1±13.8 (N=5) at 6 months, and 72.2±17.7 (N=6) at 9 months (maximum score 100).

Quality of life: Overall, quality of life improved with Mean±S.D. PEDsQL Core total score improving from 66.1±16.6 to 80.9±15.1 at 9 months (N=6, maximum score 100). These scores and improvements were consistent across total, physical and psychosocial components. Function: All 4 patients evaluated had improvements in the 6MWT at 6 months, with Mean±S.D. distance 258+87 metres at baseline and 402±82 metres at 6 months. 3 out of 5 patients noted improvements in their Movement ABC score centiles.

Conclusion: These data shows that on standardised testing, Burosumab improves the pain, function, fatigue and overall quality of life over a 9-month period for children with XLH and their families in a clinical setting.

Disclosure: MS Cheung - Advisory Panel for Kyowa Kirin International.