ESPE Abstracts

Background: Hypophosphatemia due to excess urinary phosphate losses and rachitic bone disease occur in several related disorders. The most common form of the heritable hypophosphatemic disorders, X-linked hypophosphatemia (XLH), is due to loss-of-function mutations of the osteocyte/osteoblast protein, PHEX. Reduced abundance of phosphate transporters on the luminal surface of renal tubular cells in the syngeneic animal model of XLH, and inappropriately normal (or frankly low) ...

Background: The Fibroblast Growth Factors (FGFs) are a large family of proteins including paracrine, intracrine, and endocrine FGFs. Paracrine and endocrine FGFs interact with specific cell surface receptors (FGFRs) that, via intracellular tyrosine kinase activity, initiate a cascade of downstream intracellular events. Specificity of paracrine/autocrine FGF activity is provided locally by the local production of these FGFs and their cognate receptors. In contrast, endocrine FG...

Our patient was a 19-year-old female who was referred for evaluation of secondary amenorrhea and underdeveloped secondary sexual characteristics, having undergone her first and only menstrual cycle at age 16. She had experienced four episodes of hypoglycemia during her childhood; two were associated with seizure activity. She was evaluated by endocrinology after her second episode of hypoglycemia at 3 years of age and no cause could be identified. She also had learning difficu...

Background: States of vitamin D insufficiency are important determinants of rickets, as well as osteoporosis and other common complex disorders like diabetes, cancer, and infectious diseases. Although, serum concentrations of the vitamin D metabolites are primarily driven by vitamin D supply (by diet or cutaneous synthesis), there is emerging evidence to suggest that single nucleotide variants (SNVs) are important genetic determinants.Objective and hypot...

In XLH, excess fibroblast growth factor 23 (FGF23) causes hypophosphatemia and consequent rickets, skeletal deformities, and growth impairment. The efficacy and safety of burosumab, a fully human monoclonal antibody against FGF23, was evaluated in two Phase 2 trials in children with XLH. In CL201, 52 children with XLH (5–12 years old, Tanner ≤2) were randomized 1:1 to receive subcutaneous burosumab every 2 (Q2W) or 4 (Q4W) weeks, with doses titrated up to 2 mg/kg to...

Background: In X-linked hypophosphatemia (XLH), abnormally elevated serum fibroblast growth factor 23 (FGF23) results in low renal maximum threshold for phosphate reabsorption (TmP/GFR), low serum phosphorus (Pi), inappropriately normal 1,25-dihydroxyvitamin D (1,25(OH)2D) and development of rachitic deformities.Methods: Up to four s.c. KRN23 doses were given every 28 days to 28 adults with XLH according to a dose-escalation algorithm (0.05&#1...

Background: In X-linked Hypophosphatemia (XLH), abnormally elevated serum Fibroblast Growth Factor 23 (FGF23) results in low renal maximum threshold for phosphate reabsorption (TmP/GFR), low serum phosphorus (Pi), inappropriately normal 1,25-dihydroxyvitamin D (1,25(OH)2D) and development of rachitic deformities.Methods: Up to four SC KRN23 doses were given every 28 days to 28 adults with XLH (26 completed) according to a dose-escalation algorithm (0.05&...

Objectives: In X-linked hypophosphatemia (XLH), abnormally elevated serum Fibroblast growth Factor 23 (FGF23) results in low renal maximum threshold for phosphate reabsorption, low serum phosphorus, inappropriately normal 1,25-dihydroxyvitamin D, and development of rachitic deformities. The effect of KRN23 on health-related quality of life (HRQL) was assessed.Methods: Open-label KRN23 was given s.c. every 28 days up to four doses to 28 adults with XLH (2...

In children with XLH, excess FGF23 causes hypophosphatemia with consequent rickets, skeletal deformities, and impaired growth and mobility. We previously reported that burosumab improved phosphate homeostasis and rickets in children with XLH. Here, we report final data from this Phase 2 Study CL201 (NCT02163577).Fifty-two children with XLH (5-12 years old, Tanner ≤ 2) were randomized 1:1 to receive subcutaneous burosumab every 2 (Q2W) or 4 (Q4W) we...

In children with XLH, excess FGF23 causes hypophosphatemia with consequent rickets, skeletal deformities, and impaired growth and mobility. We reported that burosumab improved phosphate homeostasis and rickets in children with XLH. Here, we present data on 11/52 subjects (all girls) who developed fused growth plates during the phase 2 study CL201 (NCT02163577).In CL201, 52 subjects (Baseline: 5-12 years-old, Tanner ≤ 2) were randomized 1:1 to recei...