Pharmacologic targeting of hypoxia-inducible factors

Hypoxia-inducible factors (HIFs) control transcriptional responses to reduced O2 availability. HIFs are heterodimeric proteins composed of an O2-regulated HIF-alpha subunit and a constitutively expressed HIF-1 beta subunit. HIF-alpha subunits are subject to prolyl hydroxylation, which targets the proteins for degradation under normoxic conditions. Small molecule prolyl hydroxylase inhibitors, which stabilize the HIF-alpha subunits and increase HIF-dependent expression of erythropoietin, are in phase III clinical trials for the treatment of anemia in patients with chronic kidney disease. HIFs contribute to the pathogenesis of many cancers, particularly the clear cell type of renal cell carcinoma in which loss of function of the von Hippel-Lindau tumor suppressor blocks HIF-2 alpha degradation. A small molecule inhibitor that binds to HIF-2 alpha and blocks dimerization with HIF-1 beta is in clinical trials for the treatment of renal cell carcinoma. Targeting HIFs for stabilization or inhibition may improve outcomes in diseases that are common causes of mortality in the US population.