Burosumab Therapy in Children with X-Linked Hypophosphatemia

Area of Science:

• Pediatric Endocrinology
• Nephrology
• Genetics

Background:

• X-linked hypophosphatemia (XLH) is a genetic disorder characterized by elevated fibroblast growth factor 23 (FGF-23).
• High FGF-23 levels lead to hypophosphatemia, rickets, osteomalacia, and skeletal deformities.

Purpose of the Study:

• To evaluate the efficacy and safety of burosumab, an FGF-23 targeting monoclonal antibody, in pediatric patients with XLH.
• To assess burosumab's impact on rickets severity, serum phosphorus levels, linear growth, and physical function.

Main Methods:

• An open-label, phase 2 trial randomized 52 children with XLH to receive subcutaneous burosumab every 2 or 4 weeks.
• Dosing was adjusted to maintain serum phosphorus at the lower end of the normal range.
• Primary endpoint: change in Thacher rickets severity score at weeks 40 and 64.

Main Results:

• Burosumab significantly reduced rickets severity scores in both dosing groups, with improvements sustained through week 64.
• Serum phosphorus levels normalized in over half of patients by week 6, and renal tubular phosphate reabsorption increased.
• Improvements were observed in linear growth, physical ability, and pain, with generally mild to moderate adverse events.

Conclusions:

• Burosumab treatment in children with XLH improves key disease markers, including phosphate reabsorption and serum phosphorus levels.
• The therapy promotes linear growth, enhances physical function, and alleviates rickets severity and pain.
• Burosumab demonstrates a favorable safety profile in the studied pediatric population.