Effect of Burosumab Compared With Conventional Therapy on Younger vs Older Children With X-linked Hypophosphatemia

Leanne M. Ward, Francis H. Glorieux, Michael P. Whyte, Craig F. Munns, Anthony A. Portale, Wolfgang Högler, Jill H. Simmons, Gary S. Gottesman, Raja Padidela, Noriyuki Namba, Hae Il Cheong, Ola Nilsson, Meng Mao, Angel Chen, Alison Skrinar, Mary Scott Roberts, Erik A. Imel

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Context: Younger age at treatment onset with conventional therapy (phosphate salts and active vitamin D; Pi/D) is associated with improved growth and skeletal outcomes in children with X-linked hypophosphatemia (XLH). The effect of age on burosumab efficacy and safety in XLH is unknown.

Objective: This work aimed to explore the efficacy and safety of burosumab vs Pi/D in younger (< 5 years) and older (5-12 years) children with XLH.

Methods: This post hoc analysis of a 64-week, open-label, randomized controlled study took place at 16 academic centers. Sixty-one children aged 1 to 12 years with XLH (younger, n = 26; older, n = 35) participated. Children received burosumab starting at 0.8 mg/kg every 2 weeks (younger, n = 14; older, n = 15) or continued Pi/D individually titrated per recommended guidelines (younger, n = 12; older, n = 20). The main outcome measure included the least squares means difference (LSMD) in Radiographic Global Impression of Change (RGI-C) rickets total score from baseline to week 64.

Results: The LSMD in outcomes through 64 weeks on burosumab vs conventional therapy by age group were as follows: RGI-C rickets total score (younger, +0.90; older, +1.07), total Rickets Severity Score (younger, −0.86; older, −1.44), RGI-C lower limb deformity score (younger, +1.02; older, +0.91), recumbent length or standing height Z-score (younger, +0.20; older, +0.09), and serum alkaline phosphatase (ALP) (younger, −31.15% of upper normal limit [ULN]; older, −52.11% of ULN). On burosumab, dental abscesses were not reported in younger children but were in 53% of older children.

Conclusion: Burosumab appears to improve outcomes both in younger and older children with XLH, including rickets, lower limb deformities, growth, and ALP, compared with Pi/D.
Original languageEnglish
Article numberdgac296
Pages (from-to)e3241-e3253
JournalJournal of Clinical Endocrinology and Metabolism
Issue number8
Publication statusPublished - 9 May 2022

Bibliographical note

© The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society.


  • X-linked hypophosphatemia
  • burosumab
  • children
  • fibroblast growth factor 23
  • rickets


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