Preeclampsia is characterized by the development of elevated blood pressure during the second and third trimesters of pregnancy that is accompanied by end organ dysfunction. The pathogenesis of preeclampsia is multifactorial but is commonly characterized by endothelial dysfunction and the overproduction of antiangiogenic factors, including the soluble VEGF (vascular endothelial growth factor) receptor sFlt-1 (soluble Fms-like tyrosine kinase receptor 1). Previously, administration of exogenous VEGF-A, bound to a carrier protein called ELP (elastin-like polypeptide), significantly reduced free sFlt-1 levels and attenuated the hypertensive response in a rodent model of preeclampsia. However, VEGF-A administration induces multifactorial effects mediated through its direct activation of the Flk-1 receptor. In response to this, we developed a therapeutic chimera using ELP bound to VEGF-B, a VEGF isoform that binds to sFlt-1 but not to Flk-1. The purpose of this study was to evaluate the in vitro activity and pharmacological properties of ELP-VEGF-B and to test its efficacy in the reduced uterine perfusion pressure rat model of placental ischemia. ELP-VEGF-B was less potent than ELP-VEGF-A in stimulation of endothelial cell proliferation and matrix invasion, indicating that it is a weaker angiogenic driver. However, after repeated subcutaneous administration in pregnant rats, ELP-VEGF-B was maternally sequestered and reduced blood pressure when compared with saline treated animals following induction of placental ischemia (123.38±11.4 versus 139.98±10.56 mm Hg, P =0.0129). Blood pressure reduction was associated with a restoration of the angiogenic capacity of plasma from rats treated with ELP-VEGF-B. ELP-VEGF-B is a nonangiogenic, maternally sequestered protein with potential efficacy for treatment of preeclampsia.

Introduction Preeclampsia is clinically characterized by the development of elevated blood pressure combined with proteinuria or other symptoms during the second and third trimester of pregnancy. sFlt‐1, a soluble form of the extracellular domain of the Flt‐1 receptor, is up‐regulated in the blood of preeclamptic women and functions as a trap for vascular endothelial growth factor (VEGF), preventing healthy VEGF signaling to endothelial cells and contributing to endothelial dysfunction. Previously, our lab has shown that administration of a VEGF isoform, VEGF‐A, bound to a carrier protein called elastin‐like polypeptide (ELP), significantly reduced free s‐Flt1 levels and normalized blood pressure in a rodent model of preeclampsia. However, VEGF‐A administration has a host of side effects mediated thorough its activation of the Flk‐1 receptor. In response to this, we have developed a separate therapeutic chimera which utilizes ELP bound to a different isoform of VEGF, VEGF‐B, that has no known interaction with the Flk‐1 receptor but still possess the potential to bind to sFlt‐1. In this study we have conducted pharmacokinetic, biodistribution, and efficacy experiments to test our hypothesis that a biopolymer chimera of VEGF‐B (ELP‐VEGF‐B) would function as a sequestrant of sFlt‐1 in order to lower blood pressure in the reduced uterine perfusion pressure (RUPP) model of preeclampsia. Methods Pharmacokinetics were determined by injecting pregnant rats with labeled protein and measuring clearance by repeated tail vein blood draws. Biodistribution and placental transfer of ELP‐VEGF‐B was determined by ex vivo imaging of organs, placentae, and pups of animals injected with labeled protein using an IVIS Spectrum In Vivo Imaging System (IVIS). Efficacy studies were conducted in pregnant SD rats from day 13 to day 18 of gestation. Pregnant SD rats received either the RUPP or sham procedure and were subsequently administered ELP‐VEGF‐B (50mg/kg) or sterile saline, subcutaneously, on days 13, 15, and 17 of gestation. Body weights were monitored daily, and blood pressure was measured, through carotid catheters, on day 18 of gestation. Animals were then sacrificed and harvested on day 18 of gestation. Results Plasma clearance of ELP‐VEGF‐B fit well into a two‐compartment pharmacokinetic model, resulting in half lives of 48.4hr(terminal) and 0.22hr (distribution). ELP‐VEGF‐B accumulated primarily in the maternal kidney, liver, and placenta, with undetectable amounts in the pups. ELP‐VEGF‐B administration had no significant effect on maternal body weight, pup weight, or placental weight amongst any of the treatment or control groups. However, administration of ELP‐VEGF‐B in a rodent model of placental ischemia did achieve a significant reduction in blood pressure when compared to saline treated animals following induction of placental ischemia (123.38 ± 11.4 versus 139.98 ± 10.56 mmHg, p=0.0129). Conclusions The biopolymer fusion peptide, ELP‐VEGF‐B, has a pharmacokinetic profile similar to our previously tested therapeutic, EL...