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Linear growth of children with X-linked hypophosphatemia treated with burosumab: a real-life observational study
Yael Levy-Shraga1,2, Shelly Levi3,4, Ravit Regev3,5
1Pediatric Endocrinology Unit, The Edmond and Lily Safra Children's Hospital, Chaim Sheba Medical Center, Tel Hashomer, 52621, Israel. yael.levy.shraga@gmail.com.
Insights
Burosumab treatment significantly improved phosphate levels, reduced rickets severity, and enhanced linear growth in pediatric patients with X-linked hypophosphatemia. This real-world evidence supports its long-term efficacy in improving patient outcomes.
Area of Science:
- Pediatric Endocrinology
- Rare Genetic Diseases
- Pharmacological Interventions
Background:
- X-linked hypophosphatemia (XLH) is a rare genetic disorder characterized by phosphate wasting and rickets.
- Conventional therapies for XLH have limitations in addressing linear growth and biochemical abnormalities.
- Burosumab, a monoclonal antibody targeting FGF23, has emerged as a targeted therapy for XLH.
Purpose of the Study:
- To evaluate the long-term efficacy of burosumab in pediatric patients with XLH.
- To assess the impact of burosumab on linear growth, biochemical parameters, and rickets severity.
- To investigate the safety and effectiveness of burosumab in a real-world clinical setting.
Main Methods:
- Multi-center retrospective study of 35 pediatric patients with XLH treated with burosumab.
- Data collected included clinical information, anthropometric measurements, laboratory results, and Rickets Severity Score (RSS) up to 4 years post-treatment initiation.
- Analysis focused on changes in serum phosphorus, phosphorus reabsorption, RSS, and height/weight z-scores.
Main Results:
- Burosumab treatment led to a sustained increase in serum phosphorus levels (p < 0.001) and improved phosphorus reabsorption (p = 0.041).
- Significant reduction in Rickets Severity Score observed, from 1.7 to 0.3 within 24 months (p < 0.001).
- Height z-score improved from -2.07 to -1.72 (p < 0.001) and weight z-score from -0.51 to -0.11 (p < 0.001).
- Concomitant growth hormone therapy in 8 patients showed no adverse effects and also contributed to height improvement.
Conclusions:
- Burosumab is effective in improving phosphate homeostasis and reducing rickets severity in pediatric XLH patients.
- The treatment demonstrates a positive impact on linear growth, with significant improvements in height z-scores.
- Real-world data support burosumab as a safe and effective therapeutic option for XLH, including in combination with growth hormone.
Abstract:
To assess the long-term efficacy of burosumab for pediatric patients with X-linked hypophosphatemia, focusing on linear growth. This multi-center retrospective study included 35 pediatric patients who began treatment with burosumab between January 2018 and January 2021. We collected clinical data, anthropometric measurements, laboratory results, and Rickets Severity Score (RSS), from 2 years prior to treatment initiation and up to 4 years after. Burosumab was initiated at a mean age of 7.5 ± 4.4 years (range 0.6-15.9), with a mean initial dose of 0.8 ± 0.3 mg/kg, which was subsequently increased to 1.1 ± 0.4 mg/kg. The patients were followed for 2.9 ± 1.4 years (range 1-4) after initiating burosumab. Serum phosphorus levels increased from 2.7 ± 0.8 mg/dl at burosumab initiation to 3.4 ± 0.6 mg/dl after 3 months and remained stable (p < 0.001). Total reabsorption of phosphorus increased from 82.0 ± 6.8 to 90.1 ± 5.3% after 12 months of treatment (p = 0.041). The RSS improved from 1.7 ± 1.0 at burosumab initiation to 0.5 ± 0.6 and 0.3 ± 0.6 after 12 and 24 months, respectively (p < 0.001). Both height z-score and weight z-score improved from burosumab initiation to the end of the study: from - 2.07 ± 1.05 to - 1.72 ± 1.04 (p < 0.001) and from - 0.51 ± 1.12 to - 0.11 ± 1.29 (p < 0.001), respectively. Eight children received growth hormone combined with burosumab treatment. Height z-score improved among those who received growth hormone (from - 2.33 ± 1.12 to - 1.94 ± 1.24, p = 0.042) and among those who did not (from - 2.01 ± 1.01 to - 1.66 ± 1.01, p = 0.001).
Conclusion:
Burosumab treatment in a real-life setting improved phosphate homeostasis and rickets severity and enhanced linear growth.
What Is Known:
• Compared to conventional therapy, burosumab treatment has been shown to increase serum phosphate levels and reduce the severity of rickets. • The effect of burosumab on growth is still being study.
What Is New:
• Height z-score improved between the start of burosumab treatment and the end of the study (-2.07 ± 1.05 vs. -1.72 ± 1.04, p < 0.001). • Eight children received burosumab combined with growth hormone treatment without side effects during the concomitant treatments.
