ESPE Abstracts (2019) 92 P3-270

A Real World, Clinical Experience of Burosumab Therapy in a Cohort of Children with X-Linked Hypophosphataemia

Jessica Sandy, Robyn Gilbey-Cross, Rui Santos, Alessandra Cocca, Sophia Sakka, Mavali Morris, Jill Massey, Moira Cheung


Evelina London Children's Hospital, London, United Kingdom


Burosumab, a monoclonal antibody targeting fibroblast growth factor 23, is now available for clinical use in children with X-linked hypophosphatemia (XLH). We explored the effects of this treatment in a clinical setting, considering biochemistry, growth, deformity, functionality, quality of life, pain and fatigue.

Methods: Clinical, biochemical, radiological and questionnaire data were reviewed at 6 and 12 months in a cohort of 8 children with XLH starting burosumab. Functionality was assessed with 6-minute walk test (6MWT) and Timed Up and GO (TUGLndon). Questionnaires included: Core Paediatric Quality of Life Inventory (PedsQL-Core), Paediatric Quality of Life multidimensional fatigue scale (PedsQL-Fatigue), and Brief Pain Index Pain Severity Score (PSS).

Results: Median age was 5.5 years (range=19 months-11 years). Table below shows radiological, biochemical and functional improvements over 12 months.

Test (Normal range)Baseline Mean±SD12 month Mean±SDP value (Paired t-test)
Phosphate (1.0-1.9mmol/L)0.7±0.11.1±0.1P<0.001
ALP* (139-347IU/L) 415±73322±70P<0.001
PTH** (10-65ng/L)31±1442±16P<0.05
Ur Ca:Creatinine(0.05-0.60)0.44±0.210.37±0.23Not significant,P=0.51
TmP/GFR1 ***(1.15-2.44)0.56±0.111.19±0.18P<0.001
Height Z-scores-2.600±0.813-2.435±0.787P<0.05
Thatcher Scores (out of 10)2.0±1.50.4±0.3P<0.05
TUG (N=5,seconds)5.7±0.54.8±0.6P<0.05
6MWT (N=4,metres)258±75447±53****P=0.05
*Alkaline Phosphatase, **Parathyroid hormone, ***Calculated ratio of renal tubular maximum phosphate reabsorption ****63-183metres below age/gender-matched norms

Deformity: Six children had lower limb deformity; varus(N=3), valgus(N=2), windswept(N=1). The most severely affected patient (intermalleolar distance=10cm) noted progression at 6 months with slight improvement by 12 months. All others noticed improvement at 12 months with reduced intercondylar/intermalleolar distances.

Pain/Fatigue: One child reported no pain. 12 month PSS decreased for 6 patients and slightly increased for one. Mean±SD PSS was 2.3±1.3 at baseline and 1.0±1.2 at 12 months (maximum score 10). Mean±SD PEDsQL-Fatigue scores were 64±19 at baseline and 76±17 at 12 months (maximum score 100,P=0.2).

Quality of Life: Mean±SD PEDsQL-Core score improved from 69±17 at baseline to 81±15 at 9 months, however decreased back to 67±17 by 12 months (N=7,maximum score 100). This is despite verbal reports of improvements and may reflect a shift in expectation.

Conclusion: In a real-world setting, burosumab can improve biochemistry, growth, deformity, pain and function in children with XLH

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