Bone Abstracts

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...

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Purpose: In X-linked hypophosphatemia (XLH), elevated serum FGF23 causes low serum phosphorus (Pi) and inappropriately normal 1,25-dihydroxyvitamin D (1,25(OH)2D) levels. We report safety, tolerability and biochemistry markers following single ascending dose administration of KRN23 in adults with XLH.Methods: 38 XLH subjects with baseline FGF23≥30 pg/ml were randomized to receive single doses of KRN23 (K) or placebo (P) either (0.003&#15...

Purpose: In X-linked hypophosphatemia (XLH), elevated serum FGF23 causes low serum phosphorus (Pi) and inappropriately normal 125-dihydroxyvitamin D (125(OH)2D) levels. We report PK and PD of KRN23 following single ascending dose administration in adults with XLH.Methods: 38 XLH patients with baseline FGF23≥30 pg/ml were randomized to receive a single dose of KRN23 (K) or placebo (P) either i.v. (0.003–0.3 mg/kg) or s.c. (0.1–1...

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Atypical femur fractures (AFF) have been associated with antiresorptive therapy. In a retrospective case-control study, we identified AFF using ASBMR 2013 criteria. Femoral shaft fractures were identified using ICD9 codes. We screened 1479 radiographs. Radiographs were excluded for high-energy trauma, tumor, or periprosthetic fracture. Two radiologists blinded to treatment scored 482 radiographs for AFF features, and jointly adjudicated discrepancies. The required AFF feature,...

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...