55. Investigational RNAI therapeutic targeting angiotensinogen (AGT) ameliorates the preeclamptic phenotype in rodent models of preeclampsia

Introduction Preeclampsia is a common and devastating pregnancy disorder, featuring hypertension and proteinuria. Studies have demonstrated that dysregulation of Renin-Angiotensin-System (RAS) is involved in the pathogenesis of the disease; however, treatment with a RAS-blocker is contraindicated due to fetal toxicity. Objective RNA interference (RNAi) is a potent means of gene-specific silencing. We sought to demonstrate maternal-specific RAS blockade by targeting maternal hepatic angiotensinogen (AGT) using small interfering RNA (siRNA). In this study we tested the ability of AGT-targeting siRNA to ameliorate symptoms of preeclampsia in two rat models, without inducing a placental pathology or affecting fetal health. Methods Two animal models of preeclampsia were used. The first model (transgenic) acts by upregulation of the circulating and uteroplacental Renin-Angiotensin-System (RAS). The second model is a surgical model that induces ischemia/reperfusion injury and subsequent local and systemic inflammation restriction (RUPP). Beginning on day 3 of gestation, transgenic rats were dosed subcutaneously with 10 mg/kg siRNA every third day through gestation day 15. In RUPP rats, siRNA was subcutaneously injected once (10 mg/kg) on day 12 of gestation. Results The major finding is that RNAi therapeutics targeting maternal hepatic AGT ameliorated the preeclamptic phenotype in both models. We were able to selectively reduce maternal RAS signaling while preserving the fetal RAS. In the transgenic model, silencing of hAGT leads to a reduction of blood pressure and urinary albumin excretion. Moreover, we improved intrauterine growth retardation, indicating an improved fetal development. The RUPP model confirmed the principal findings in a model that is not explicitly driven by the RAS. Discussion Investigational RNAi therapeutics targeting AGT ameliorated the clinical sequelae of preeclampsia in a transgenic rat model and improved the outcome of the fetus. We conclude that maternal specific RAS blockade improves maternal symptoms without deteriorating fetal health in rodent models.