Anemia is common disease and is associated with many conditions, including end-stage renal disease. Recombinant versions of Erythropoeitin (EPO), the key hormone that regulates red blood cell mass, have been a mainstay of treatment for this condition. The necessity of parenteral administration, however, has prompted the search for alternative methods for increasing red cell mass. In this regard, a subset of patients with erythrocytosis harbor loss of function mutations in the Prolyl Hydroxylase Domain protein 2 (PHD2, also known as EGLN1) gene, thereby identifying the encoding protein, PHD2, as an attractive target to increase red cell mass. PHD2 is the key enzyme that downregulates Hypoxia Inducible Factor-? (HIF-?), which, in turn, activates the EPO gene. Indeed there are efforts underway elsewhere to inhibit the active site of PHD2 as an approach to treating anemia. However, the catalytic domain of PHD2 is homologous to other proteins, thereby warranting efforts to more specifically inhibit PHD2. PHD2 is distinctive in harboring a zinc finger domain that, like its catalytic domain, is essential for efficient downregulation of HIF-?. In the present application, we propose targeting this zinc finger in order to increase HIF-? and thereby increase red cell mass. In preliminary studies, we have conducted an Alpha Screen for compounds that can inhibit the interaction between the zinc finger of PHD2 and its ligand, which serves to recruit PHD2 to the HSP90 pathway to facilitate HIF-? hydroxylation. We have identified compounds that can disrupt this interaction. We propose the following Specific Aims. First, we wish to identify structure activity relationships with the aim of improving inhibition. Second, we seek to attain acceptable ADME/PK drug values for at least one or two compounds. Third, we propose injecting this compound(s) into a novel knockin mouse line in which the Phd2 gene has a humanized zinc finger so as to allow interaction with compounds identified by the in vitro studies. Accordingly, this application involves a partnership that brings together the medicinal chemistry expertise of the Fox Chase Chemical Diversity Center with the experience of the Principal Investigator?s laboratory at the University of Pennsylvania in examining the HIF pathway. The long term goal of this project will be to identify a preclinical candidate that can be evaluated in more detailed IND-directed studies. Such a candidate will be promising agent for the treatment of anemia.
The oxygen sensor PHD2 regulates the hormone Erythropoeitin and therefore red cell mass. We propose inhibiting the activity of a key domain of PHD2, namely its zinc finger, with small molecules. Such compounds will have utility in the treatment of anemia, which is characterized by low red cell mass.
