Bone Abstracts

Objective: We constructed height growth curves for children with XLH from birth to early adolescence, a majority of whom received conventional therapy consisting of multiple daily doses of oral phosphate and active vitamin D.Methods: Growth data from four clinical studies were pooled to construct the growth curves. UX023-CL002 was an observational, retrospective chart review of 103 children with XLH, 1–14 years of age. Pre-treatment data were collec...

Objectives: XLH features renal phosphate (Pi) wasting, hypophosphatemia, rickets, and skeletal deformities from elevated circulating levels of fibroblast growth factor 23 (FGF23). KRN23, an investigational fully human monoclonal antibody, binds FGF23 and inhibits its action. Our Phase 2 study of KRN23 in XLH children (ages 5–12 years) is demonstrating improvements in serum Pi and rickets. Here we present our Phase 2 trial evaluating the efficacy and safety of KRN23 in you...

Objectives: In XLH, FGF23-mediated hypophosphatemia leads to defective bone mineralization and rickets. Investigational product KRN23 binds FGF23 and inhibits its activity. The objective of this Phase 2 study was to evaluate the safety and efficacy of KRN23 in 52 children with XLH (ages 5–12 years, ≤Tanner 2).Methods: Patients were randomized to receive KRN23 biweekly (Q2W) or monthly (Q4W) by SC injection. KRN23 dose was titrated (maximum 2 m...

Objectives: In XLH, musculoskeletal outcomes of current treatment with oral phosphate (Pi)/active vitamin D are suboptimal for many patients. In a Phase 2, open-label study, we tested the hypothesis that KRN23 improves rickets and functional outcomes in XLH children.Methods: Fifty-two children with XLH (ages 5–12 years at baseline) received KRN23 subcutaneously biweekly (Q2W) or monthly (Q4W). At study entry, most participants had received oral Pi/a...

Objective: We evaluated the long-term efficacy of burosumab, a monoclonal antibody against FGF23, in a Phase 2 Study (NCT02163577) in children with XLH.Methods: Fifty-two children with XLH (5-12 years-old, Tanner ≤ 2) were randomized 1:1 to receive subcutaneous burosumab Q2W or Q4W for 64 weeks. Doses were titrated up to 2 mg/kg/dose targeting serum phosphorus levels within 1.1–1.6 mmol/l. All subjects entered the long-term extension at Week 6...

Objective: We compared the efficacy and safety of burosumab, a monoclonal antibody against FGF23, to conventional therapy [oral phosphate and active vitamin D (Pi/D)] in children with X-linked hypophosphatemia (XLH).Methods: In this Phase 3 trial (NCT02915705), 61 children with XLH (1-12 years-old) were randomized 1:1 after a 7-day Pi/D washout to receive burosumab starting at 0.8 mg/kg SC Q2W or reinitiate Pi/D optimally titrated by investigators. Eligi...