Preclinical development of a dual targeting bicistronic gene therapy approach for the treatment of wet age-related macular degeneration

Age-related macular degeneration (AMD) continues to be a leading cause of severe vision impairment affecting millions worldwide. The late stages of AMD are characterized by outer retinal atrophy (geographic atrophy, GA), or neovascularization associated with subretinal and/or intraretinal exudation (exudative neovascular or ‘wet’ AMD). Intravitreal (IVT) administration of anti-vascular endothelial growth factor (VEGF) therapies has dramatically improved vision preservation for wet AMD (wAMD) patients. However, current Standard of Care (SoC) has significant shortcomings and the benefits of anti-VEGF therapy in the real-world setting fall short of the vision gains observed in randomized clinical trials. This is thought to be attributable to drug burden to patients, lack of therapeutic durability due to progression of underlying macular atrophy and refractility to treatment. Vectorized anti-VEGF therapy has been shown to be effective in reducing drug burden clinically but is unlikely to address the progression of the underlying GA driven by complement-mediated inflammation. Here, we aim to address this unmet need by developing a bicistronic gene therapy vector co-expressing aflibercept and Factor H-like protein 1 (FHL-1) to target the pro-angiogenic and pro-inflammatory environment of wAMD. In vitro assays confirmed the anti-angiogenic and complement inhibitory properties of the bicistronic vector. Recombinant AAV8 (rAAV8)-mediated co-expression was detected for up to 4 weeks following subretinal delivery in wild type (WT) mice. In a mouse laser-induced choroidal neovascularization (CNV) model, subretinal delivery of bicistronic vectors significantly reduced both CNV leakage and lesion. These results demonstrate that a single subretinal administration of bicistronic vector may provide an effective treatment option for wAMD and may also prolong patient’s visual outcomes by preventing the underlying progression of GA.