Plasma Kallikrein Mediates Vascular Endothelial Growth Factor-Induced Retinal Dysfunction and Thickening.

PURPOSE: Plasma kallikrein is a serine protease and circulating component of inflammation, which exerts clinically significant effects on vasogenic edema. This study examines the role of plasma kallikrein in VEGF-induced retinal edema. METHODS: Intravitreal injections of VEGF and saline vehicle were performed in plasma prekallikrein-deficient (KLKB1-/-) and wild-type (WT) mice, and in both rats and mice receiving a selective plasma kallikrein inhibitor, VA999272. Retinal vascular permeability (RVP) and retinal thickness were measured by Evans blue permeation and optical coherence tomography, respectively. The retinal kallikrein kinin system was examined by Western blotting and immunohistochemistry. Retinal neovascularization was investigated in KLKB1-/- and WT mice subjected to oxygen-induced retinopathy. RESULTS: Vascular endothelial growth factor-induced RVP and retinal thickening were reduced in KLKB1-/- mice by 68% and 47%, respectively, compared to VEGF responses in WT mice. Plasma kallikrein also contributes to TNFα-induced retinal thickening, which was reduced by 52% in KLKB1-/- mice. Systemic administration of VA999272 reduced VEGF-induced retinal thickening by 57% (P < 0.001) in mice and 53% (P < 0.001) in rats, compared to vehicle-treated controls. Intravitreal injection of VEGF in WT mice increased plasma prekallikrein in the retina, which was diffusely distributed throughout the inner and outer retinal layers. Avascular and neovascular areas induced by oxygen-induced retinopathy were similar in WT and KLKB1-/- mice. CONCLUSIONS: Vascular endothelial growth factor increases extravasation of plasma kallikrein into the retina, and plasma kallikrein is required for the full effects of VEGF on RVP and retinal thickening in rodents. Systemic plasma kallikrein inhibition may provide a therapeutic opportunity to treat VEGF-induced retina edema.

New benzylureas as a novel series of potent, nonpeptidic vasopressin V2 receptor agonists.

Vasopressin (AVP) is a hormone that stimulates an increase in water permeability through activation of V2 receptors in the kidney. The analogue of AVP, desmopressin, has proven an effective drug for diseases where a reduction of urine output is desired. However, its peptidic nature limits its bioavailability. We report herein the discovery of potent, nonpeptidic, benzylurea derived agonists of the vasopressin V2 receptor. We describe substitutions on the benzyl group to give improvements in potency and subsequent modifications to the urea end group to provide improvements in solubility and increased oral efficacy in a rat model of diuresis. The lead compound 20e (VA106483) is reported for the first time and has been selected for clinical development.

Non-peptide oxytocin agonists.

A library of compounds targeted to the vasopressin/oxytocin family of receptors was screened for activity at a cloned human oxytocin receptor using a reporter gene assay. Potency and selectivity were optimised to afford compound 39, EC50 = 33 nM. This series of compounds represents the first disclosed, non-peptide, low molecular weight agonists of the hormone oxytocin (OT).