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Anemia linked to a relative deficiency of renal erythropoietin production is a significant cause of morbidity and medical expenditures in the developed world. Recombinant erythropoietin is expensive and has been linked to excess cardiovascular events. Moreover, some patients become refractory to erythropoietin because of increased production of factors such as hepcidin. During fetal life, the liver, rather than the kidney, is the major source of erythropoietin. In the present study, we show that it is feasible to reactivate hepatic erythropoietin production and suppress hepcidin levels using systemically delivered siRNAs targeting the EglN prolyl hydroxylases specifically in the liver, leading to improved RBC production in models of anemia caused by either renal insufficiency or chronic inflammation with enhanced hepcidin production.

Abstract 3161 Anemia in chronic kidney disease patients due to impaired renal production of erythropoietin (EPO) and insufficient erythropoiesis is a significant public health problem. One approach to compensate for the low EPO levels in patients with impaired kidney function would be to stimulate the levels of EPO production from non-renal sources. It is well known that during fetal development the liver serves as the primary producer of EPO until the kidney becomes the dominant source after birth. Negative regulation of EPO production is mediated by the EGLN family of prolyl hydroxylases (PHDs1-3) that play an important role in oxygen sensing by targeting the transcription factor hypoxia inducible factor (HIF) for degradation via the proteasome. HIF stabilization and activity is required to mediate EPO gene transcription. Previously it has been shown that liver specific conditional knockout of all three PHDs is required to activate HIF and induce EPO production in liver (Minamishima et al. Science 2010). Here we show that simultaneous siRNA mediated knockdown of all 3 PHD genes in mouse liver using lipid nanoparticles (LNPs) can induce hepatic EPO mRNA activation, elevation of serum EPO levels and stimulation of erythropoiesis. We extend these data by examining siRNA knockdown of different combinations of the 3 PHD genes and demonstrate that PHD2 is the dominant PHD gene regulating hepatic EPO production. In addition, due to the specificity of the LNP delivery system we show that the HIF activation and increase in EPO mRNA occurs specifically in liver. Increases in serum EPO and hematocrit were durable for two weeks and one month after a single intravenous dose of LNP siRNA. Furthermore, PHD siRNA silencing in a 5/6 nephrectomy model successfully elevates hemoglobin levels and corrects anemia. In conclusion, targeting of EGLN prolyl hydroxylase genes with siRNA therapeutics has potential in the treatment of anemia associated with chronic kidney disease and provides liver-specific target gene regulation. Disclosures: Querbes: Alnylam Pharmaceuticals: Employment. Bogorad:Alnylam Pharmaceuticals: Research Funding. Moslehi:Alnylam Pharmaceuticals: Honoraria. Akinc:Alnylam Pharmaceuticals: Employment. Wong:Alnylam Pharmaceuticals: Employment. Zurenko:Alnylam Pharmaceuticals: Employment. Qin:Alnylam Pharmaceuticals: Employment. Hettinger:Alnylam Pharmaceuticals, Inc.: Employment. Kuchimanchi:Alnylam Pharmaceuticals: Employment. Charisse:Alnylam Pharmaceuticals: Employment. Sah:Alnylam Pharmaceuticals, Inc.: Employment. Fitzgerald:Alnylam Pharmaceuticals: Employment. Kotelianski:Alnylam Pharmaceuticals: Employment. Kaelin:Fibrogen: Consultancy, Equity Ownership.