A Single Dose of EGLN1 siRNA Yields Increased Erythropoiesis in Nonhuman Primates

Abstract

Decreased production of erythropoietin (EPO) causes anemia in patients with chronic kidney disease, and recombinant human EPO is used to treat renal failure associated anemia. The liver, the main EPO-producing organ in utero, maintains the capacity to produce EPO in the adult but in insufficient quantities to restore hemoglobin levels to normal in patients with impaired renal function. Inhibition of prolyl-4-hydroxylase domain (PHD) proteins is known to cause an increase in EPO production through its effects on hypoxia inducible factor. Here, we utilized small interfering RNA (siRNA) targeting EGLN1, the gene encoding the PHD2 protein, to investigate the phenotypic consequences in nonhuman primates. A single, well-tolerated intravenous dose of an optimized EGLN1 siRNA encapsulated in a lipid nanoparticle formulation caused robust mRNA silencing in the liver, leading to increases in serum EPO and hemoglobin. The siRNA-induced erythropoiesis was dose-dependent and was sustained for at least 2 months. These data point to the potential for an RNA interference-based, liver-targeted therapeutic approach for the treatment of anemia.

Discovery of Orally Bioavailable and Liver-Targeted Hypoxia-Inducible Factor Prolyl Hydroxylase (HIF-PHD) Inhibitors for the Treatment of Anemia

“… Indeed, Minamishima and Kaelin have shown that liver-selective deletion of PHD1/2/3 in mice resulted in increased serum EPO levels that paralleled the mRNA levels in liver and exceeded those achieved by renal PHD2 knockout . Consistent with the hypothesis, liver-selective knockdown with PHD2 siRNA in rhesus led to clinically relevant increases in hemoglobin . In addition, we have demonstrated that a systemic HIF-PHD inhibitor (HIF-PHDi) had increased systolic PAP (sPAP) in a dose-dependent manner in a telemetered rat model (see Figure ).…”

“…20 Consistent with the hypothesis, liverselective knockdown with PHD2 siRNA in rhesus led to clinically relevant increases in hemoglobin. 21 In addition, we have demonstrated that a systemic HIF-PHD inhibitor (HIF-PHDi) had increased systolic PAP (sPAP) in a dose-dependent manner in a telemetered rat model (see Figure 2). 22 With this supporting evidence in mind, we undertook a discovery effort to identify a hepatoselective HIF-PHD inhibitor.…”