X-linked hypophosphatemia: burosumab bests conventional therapy

  • Lancet

  • International Clinical Digest
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Takeaway

  • For children with X-linked hypophosphatemia, burosumab (Crysvita) bested conventional therapy for rickets improvement, mobility, and growth trajectories in this phase 3 trial.
  • Results suggest a therapeutic advantage for burosumab.

Why this matters

  • Conventional therapy for this condition involves vitamin D and oral phosphate, but children often still have rickets and growth restriction.
  • Burosumab targets fibroblast growth factor 23, which is elevated with this inheritable bone disease.

Key results

  • At 40 and 64 weeks, children receiving trial drug had better radiographic scores (P<.0001 vs those on conventional therapy.>
  • More children on burosumab had rickets healing at week 40:
    • 72% vs 6% with conventional therapy;
    • OR, 39 (95% CI, 7-212; P<.0001>
  • By week 64, 87% on burosumab had healing vs 19% with conventional therapy (OR, 34; 95% CI, 6-206; P=.0002). 
  • Alkaline phosphatase activity decreased more steeply with burosumab (P<.0001 z-scores for length and height were greater p=".0490)," mobility scores better>
  • Children on trial drug had more treatment-emergent adverse events (59% vs 22% in conventional therapy).

Study design

  • Randomized, active-controlled, open-label trial, 16 sites, 29 children receiving burosumab and 32 conventional therapy.
  • Funding: Ultragenyx Pharmaceutical; Kyowa Kirin International. 

Limitations

  • Small numbers, open label.

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