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Abstract: FR-PO162

Improvement in Biomarkers in Pediatric X-Linked Hypophosphatemic Rickets After 1 Year of Treatment with Burosumab

Session Information

Category: Bone and Mineral Metabolism

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Paloian, Neil J., University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
  • Nemeth, Blaise A., University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
  • Modaff, Peggy, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
  • Steiner, Robert, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
Background

X-linked hypophosphatemic rickets (XLH) is the most common genetic cause of rickets in children. Burosumab, an FGF-23 monoclonal antibody, was approved in 2018 for the treatment of XLH. Prior therapy consisted of phosphate supplementation and calcitriol, but therapeutic response was often incomplete. Clinical trial results with burosumab have been promising, but real world data regarding effectiveness in clinical practice is lacking.

Methods

11 patients <= 18 years with XLH and treated with burosumab were identified, all of whom received calcitriol and phosphorus prior to starting burosumab. Retrospective laboratory data obtained during standard of care visits was analyzed. Monthly laboratory testing was performed for 3 months after intiation of burosumab and with dose changes. Serum phosphorus, alkaline phosphatase, PTH, and urinary fractional excretion of phosphorus were measured. Statistical analysis utilized paired T-test with p<0.05 deemed significant.

Results

The mean age of patients was 7 years old (range 2 -18). The mean length of burosumab therapy was 9.7 months (range 6-11 months). The mean pre-treatment and post-treatment lab values are displayed in Table 1. Mean serum phosphorus and alkaline phosphatase over time is displayed in Image 1. Fractional excretion of phosphorus fell below 15% in 82% of our patients following treatment with burosumab.

Conclusion

Burosumab, a newly approved FGF-23 monoclonal antibody, is effective in improving the biochemical profile of children with X-linked hypophosphatemic rickets previously treated with phosphorus and calcitriol.

 Pre-burosumab1 month after burosumabp-value*Most recent lab on burosumab#p-value**
Phosphorus (mg/dL)2.63.40.0043.4<0.001
Alkaline phosphatase (U/L)5935020.01366<0.001
intact PTH (pg/mL)83.855.40.0153.80.02
FE phosphorus (%)3390.04120.01

* One month on burosumab vs pre-burosumab ** Most recent labs vs pre-burosumab # Mean 8.2 months after burosumab initiation

Mean serum values. Month 0 = pre-burosumab