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CRYSTAL STRUCTURE OF PHD2 CATALYTIC DOMAIN (CID 7465) IN COMPLEX WITH AKB-6548 AT 1.8 A RESOLUTION
Structural highlights
DiseaseEGLN1_HUMAN Defects in EGLN1 are the cause of familial erythrocytosis type 3 (ECYT3) [MIM:609820. ECYT3 is an autosomal dominant disorder characterized by increased serum red blood cell mass, elevated serum hemoglobin and hematocrit, and normal serum erythropoietin levels.[1] [2] FunctionEGLN1_HUMAN Cellular oxygen sensor that catalyzes, under normoxic conditions, the post-translational formation of 4-hydroxyproline in hypoxia-inducible factor (HIF) alpha proteins. Hydroxylates a specific proline found in each of the oxygen-dependent degradation (ODD) domains (N-terminal, NODD, and C-terminal, CODD) of HIF1A. Also hydroxylates HIF2A. Has a preference for the CODD site for both HIF1A and HIF1B. Hydroxylated HIFs are then targeted for proteasomal degradation via the von Hippel-Lindau ubiquitination complex. Under hypoxic conditions, the hydroxylation reaction is attenuated allowing HIFs to escape degradation resulting in their translocation to the nucleus, heterodimerization with HIF1B, and increased expression of hypoxy-inducible genes. EGLN1 is the most important isozyme under normoxia and, through regulating the stability of HIF1, involved in various hypoxia-influenced processes such as angiogenesis in retinal and cardiac functionality.[3] [4] [5] [6] [7] Publication Abstract from PubMedPharmacological inhibition of prolyl-4-hydroxylase domain (PHD) enzymes stabilizes hypoxia-inducible factors (HIFs), transcription factors that activate target genes that, among others, increase erythropoietin (EPO) synthesis, resulting in the production of new red blood cells (RBCs). Herein, we summarize the preclinical characteristics of the small molecule HIF prolyl-4-hydroxylase inhibitor vadadustat (AKB-6548), which is in development for the treatment of anemia in patients with chronic kidney disease (CKD). Vadadustat inhibits enzyme activity of all three human PHD isozymes, PHD1, PHD2, and PHD3, with similar low nanomolar inhibitory constant values. PHD enzyme inhibition by vadadustat is competitive with endogenous cofactor 2-oxoglutarate and is insensitive to free iron concentration. In the human hepatocellular carcinoma cell line (Hep 3B) and human umbilical vein endothelial cells, PHD inhibition by vadadustat leads to the time- and concentration-dependent stabilization of HIF-1a and HIF-2a. In Hep 3B cells, this in turn results in the synthesis and secretion of EPO; vascular endothelial growth factor is not measured at detectable levels. A single oral dose of vadadustat in rats potently increases circulating levels of EPO, and daily oral dosing for 14 days increases RBC indices in healthy rats and in the 5/6 nephrectomy model of CKD. In mice and dogs, once-daily repeat oral dosing increases hemoglobin and hematocrit. Vadadustat has a relatively short half-life in all non-clinical species evaluated and does not accumulate when administered as a single bolus dose (oral or IV) or upon repeat oral dosing. The pharmacological profile of vadadustat supports continued development for treatment of renal anemia. Significance Statement Vadadustat (AKB-6548) is an orally bioavailable small molecule prolyl-4-hydroxylase inhibitor in development for anemia of chronic kidney disease. It is an equipotent inhibitor of the three human PHD isoforms, which activates erythropoiesis through stabilization of HIF-1a and HIF-2a, increasing production of EPO, without detectable stimulation of VEGF. Preclinical characterization of vadadustat (AKB-6548), an oral small molecule hypoxia inducible factor prolyl-4-hydroxylase inhibitor, for the potential treatment of renal anemia.,Zuk A, Si Z, Loi S, Bommegowda S, Hoivik D, Danthi S, Molnar G, Csizmadia V, Rabinowitz M J Pharmacol Exp Ther. 2022 Aug 4. pii: jpet.122.001126. doi:, 10.1124/jpet.122.001126. PMID:35926869[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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