VE-4840, an oral plasma kallikrein inhibitor, decreases human plasma kallikrein and VEGF-induced retinal thickening and vascular permeability

Abstract

Purpose : This study investigates the effects of an orally dosed plasma kallikrein inhibitor on human plasma kallikrein (hPK) and VEGF-induced models of retinal thickening and vascular permeability, two proteins contributing to retinal vascular dysfunction in diabetic retinopathy.

Methods : Enzyme inhibition: Enzyme activity of plasma kallikrein and related serine proteases were monitored by fluorescent peptide substrates. Inhibition kinetics was determined by pre-incubating the compound with plasma kallikrein and then measuring enzyme activity.
Pharmacokinetics: Male Sprague Dawley rats were treated by the parent VE-4839 (1mg/kg) intravenously or the prodrug VE-4840 orally (5mg/kg) and plasma concentrations were determined by LC-MS/MS.
In vivo assays: Retinal thickening was induced by intravitreal injection (IVT) of hPK (50ng/eye) or VEGF (100ng/eye) in male Brown Norway rats treated orally with VE-4840 (35mg/kg or 105mg/kg) or vehicle. Retinal thickness was measured by OCT before and 24hrs after IVT. Fluorescein angiography was performed on VEGF IVT eyes and retinal vascular permeability (RVP) was quantified computationally; a higher value equates to less observed RVP. Results are expressed as mean ±SD.

Results : VE-4839 has a 13nM IC50 for hPK. Selectivity over related serine proteases is >150 fold. Kinetic data is consistent with a reversible covalent mechanism of inhibition. The oral bioavailability of prodrug VE-4840 is 14.7%. Oral dosing 35mg/kg of VE-4840 reduced hPK-induced retinal thickening (22.7 ± 13.8 µm; n=6) compared to vehicle treatment (64.7 ± 21.6 µm; n=4; p= 0.0053). VE-4840 (105mg/kg) also reduced VEGF-induced retinal thickening (48.6 ± 13.2 µm; n= 8) compared to vehicle treatment (70.2 ± 5.6 µm; n= 5; p= 0.0055). Further, oral dosing with VE-4840 significantly reduced VEGF-induced RVP (39.58 ± 7.48 a.u.) compared to vehicle treatment (26.59 ± 9.27 a.u.; p= 0.0250).

Conclusions : Our results demonstrate that inhibition of the activated plasma kallikrein-kinin system with a potent plasma kallikrein inhibitor can decrease plasma kallikrein and VEGF mediated retinopathy. A reversible covalent mechanism of action may yield beneficial pharmacodynamic properties. Orally dosing VE-4840 significantly decreases retinal thickening and retinal vascular permeability.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.