RGX-314, an AAV8 expressing an anti-VEGF protein, strongly suppresses subretinal neovascularization and vascular leakage in mouse models

Abstract

Purpose : To test the efficacy of RGX-314, an AAV serotype 8 expressing an anti-VEGF Fab, in transgenic mouse models expressing human VEGF

Methods : Transgenic mice in which the rhodopsin promoter drives expression of VEGF₁₆₅ in photoreceptors (rho/VEGF mice) had a subretinal injection of RGX-314 with doses ranging from 3x10⁶-1x10¹⁰ genome copies (GC), 1x10¹⁰ GC of null vector, or PBS in one eye (n=10 per group) at P14. At P21, the area of subretinal neovascularization (SNV) per eye was measured. Double transgenic mice with doxycycline (DOX)-inducible expression of VEGF₁₆₅ in photoreceptors (Tet/opsin/VEGF mice) had a subretinal injection of 1x10⁸-1x10¹⁰ GC of RGX-314 in one eye and no injection in the fellow eye or 1x10¹⁰ GC of null vector in one eye and PBS in the fellow eye. Ten days after injection, 2mg/ml of DOX was added to drinking water and after 4 days fundus photos were graded for presence of total, partial, or no retinal detachment (RD). RGX-314 transgene product levels were measured one week after subretinal injection of 1x10⁸-1x10¹⁰ GC of RGX-314 in adult mice by ELISA analyses of eye homogenates.

Results : Compared to eyes of rho/VEGF mice injected null vector, those injected with ≥1x10⁷ GC of RGX-314 had significant reduction in mean area of SNV, with modest reduction in eyes injected with ≤3x10⁷ and >50% reduction in eyes injected with ≥1x10⁸ GC. Eyes injected with 3x10⁹ or 1x10¹⁰ GC had almost complete elimination of SNV (p<0.01). In Tet/opsin/VEGF mice, compared to the null vector group in which 100% of eyes had total RD, there was significant reduction in exudative RD in eyes injected with ≥3x10⁸ GC of RGX-314 and reduction of total detachments by 70-80% in eyes injected with 3x10⁹ or 1x10¹⁰ GC (p<0.01). The majority of eyes injected with ≤1x10⁹ GC of RGX-314 had protein levels below the limit of detection, but all eyes injected with 3x10⁹ or 1x10¹⁰ GC had detectable levels with mean level per eye 342.7ng and 286.2ng.

Conclusions : Gene therapy by subretinal injection of RGX-314 caused dose dependent suppression of SNV in rho/VEGF mice with near complete suppression with doses of 3x10⁹ or 1x10¹⁰ GC. These same doses showed robust protein product expression and markedly reduced total exudative RD in Tet/opsin/VEGF mice.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.