Vadadustat is an investigational hypoxia-inducible factor prolyl hydroxylase inhibitor that increases endogenous erythropoietin production and has been shown to decrease hepcidin levels, ameliorate iron restriction, and increase hemoglobin concentrations in anemic patients with chronic kidney disease (CKD). In studies of physiological responses to other erythropoietic stimuli, erythropoietin induced erythroblast secretion of erythroferrone (ERFE), which acts on the liver to suppress hepcidin production and mobilize iron for erythropoiesis.