Linglart A, Imel EA, Whyte MP, et al. - Findings demonstrate good tolerability as well as efficacy of burosumab in improving phosphate homeostasis and rickets in children with X-linked hypophosphatemia (XLH) when administered for 160 weeks. Long-term safety was shown to be consistent with the reported safety profile of burosumab.

• This study presents follow-up outcomes up to 160 weeks from an open-label, multicenter, randomized, dose-finding trial of burosumab for 5 to 12 year-old children with XLH.

• Patients (n=26) were randomly assigned 1:1 to burosumab every 2 weeks (Q2W) or every 4 weeks (Q4W) for 64 weeks, with dosing titrated depending on fasting serum phosphorus levels between baseline and Week 16.

• All patients were given Q2W burosumab from Week 66 to Week 160.

• Total Rickets Severity Score significantly reduced by 0.9±0.1 from baseline to Week 160 in 41 children with open distal femoral and proximal tibial growth plates (from both treatment groups).

• Burosumab led to sustained fasting serum phosphorus increases, throughout the study.

• Mild to moderate severity of adverse events was reported mostly.