Development of an RNA Targeting Based Gene Therapy Product for Neovascular Age-Related Macular Degeneration (nAMD)

Abstract

Purpose : Age-related macular degeneration (AMD) is a major cause of visual dysfunction for adults over age 50, with the neovascular AMD (nAMD) accounting for 90% of blindness in AMD. The gene therapy product HG202 used an unique strategy of rAAV vector combined with high-fidelity CRISPR/Cas13 RNA targeting technology to knock down the expression of VEGFA. The purpose of this study was to demonstrate that a single subretinal treatment of HG202 was effective at suppressing expression of VEGFA and reducing neovascularization in the eye.

Methods : Adult C57BL/6J mice were injected with HG202, Aflibercept (antibody control), AAV-antiVEGF Fab (AAV control) or vehicle. At 8 weeks post-subretinal injection of AAV or vehicle, the treated mice received three laser burns per eye to induce choroidal neovascularization (CNV). In antibody control group, the mice were treated with Aflibercept (10μg/eye) by intravitreal injection right after laser photocoagulation. Fundus fluorescein angiography (FFA) and Optical Coherence Tomography (OCT) were conducted 7 days after injury. Afterwards, choroidal flatmounts were immunostained for CNV detection.

Results : More than 40% Vegfa mRNA expression was suppressed by subretinal delivery of HG202 at the optimal dose in mouse eyes (p<0.01). The area of laser-induced CNV was markedly reduced in eyes treated with HG202 at the optimal dose (87% reduction compared to the vehicle control; p<0.0001). By contrast, the inhibition efficiency of AAV-antiVEGF Fab and Aflibercept were both lower than that of HG202 (70% reduction for AAV-antiVEGF Fab and 47% reduction for Aflibercept, compared to the vehicle control; p<0.01). Additionally, HG202 was well tolerated in mouse at certain dose range.

Conclusions : Different from DNA editing or protein inhibitors, we blocked VEGFA signaling by Cas13-mediated mRNA knockdown, which enabled high efficacy and theoretically avoided permanently changes of DNA sequence. As a result, we have demonstrated that HG202 could downregulate VEGFA expression and reduce neovascularization with high efficiency. This RNA targeting-based gene therapy is set to become a valuable treatment option for patients with nAMD. A follow-on clinical trial is warranted.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.