FP378BASELINE LEVELS OF FGF23 AND EFFECTS OF ETELCALCETIDE

Abstract

Introduction and Aims: Etelcalcetide (ETL) is a novel intravenous calcimi-metic treatment for patients with secondary hyperparathyroidism (SHPT) on hemodialysis (HD). Its efficacy is independent from baseline levels of parathyroid hormone (PTH). Data have suggested that calcitriol has attenuated ability to reduce PTH in the presence of high serum fibroblast growth factor 23 (FGF23) levels, but the effects of ETL on PTH lowering across baseline FGF23 levels is unknown. Methods: We performed a post-hoc analysis based on pooled data from two identical placebo-controlled studies that evaluated the efficacy of ETL in lowering PTH levels in adults on HD with PTH > 400 pg/mL. Patients received ETL for 26 weeks (titrated from 5mg to 15mg IV TIW) to achieve a PTH < 300 pg/mL. We stratified ETL-treated patients by quartiles of their baseline intact FGF23 (Kainos) and report concentrations of PTH at baseline and at completion of the efficacy assessment phase (EAP: weeks 20-27). In addition median baseline calcium (CA), phosphorus (P), and Ca-P product (CaxP) and FGF23, doses of ETL and Vitamin D during the EAP are reported. Results: Baseline FGF23 levels varied widely (403-27,567 pg/ml) across quartiles at baseline (Table). The median baseline PTH also varied significantly across the quartiles of FGF23, though within a much narrower range. Both baseline median phosphate concentration and median CaxP product increased with higher baseline FGF23 category in which doses of vitamin D were also higher. PTH decline induced by ETL was robust in all baseline FGF23 categories. Conclusions: Etelcalcetide effectively lowers PTH across all different baseline categories of FGF23. Baseline FGF23 concentrations do not indicate severity of secondary hyperparathyroidism, but are associated with baseline phosphate concentration, baseline CaxP product, and baseline dose of vitamin D. [Table Presented].