Recombinant AAV-Mediated Delivery of Complement Factor I (CFI) as a Potential Therapeutic Strategy for Dry Age-Related Macular Degeneration with Geographic Atrophy

Abstract

Purpose : Geographic atrophy (GA), late stage of dry age-related macular degeneration (AMD) is characterized by progressive functional loss and death of retinal pigment epithelium (RPE) and photoreceptor cells, leading to vision decline. Activation of the complement cascade is implicated in GA development; inhibiting the complement cascade reaction reduced GA progression.
Pegcetacoplan injection, targeting complement C3, is approved for the treatment of dry AMD. Complement factor I (CFI), an endogenous inhibitor in the complement pathway, plays a role in regulating the C3. Sustained expression of CFI in ocular tissues may inhibit complement activation in dry AMD patients, preventing progression of GA.
Recombinant adeno-associated virus (rAAV) has potential as a gene therapy vector in ophthalmology due to its non-pathogenic, non-integrative, replication-defective nature, low immunogenicity, strong tissue specificity, and the ability to enable long-term expression of therapeutic genes. We aim to develop a targeted gene therapy strategy for treating the progression of dry AMD.

Methods : We constructed a plasmid, pAAV-CB-hCFI, capable of expressing CFI, and validated its expression levels in HEK-293 and ARPE-19 cells. CFI was packaged into a novel AAV capsid variant with high transduction efficiency for retinal pigment epithelial cells. Subretinal injections were performed at a dose of 8E9 vg/mouse (n=4), with PBS as the control group. Five days post-injection, CFI expression in the retinas was observed, and serum C3 levels were assessed.

Results : High levels of CFI expression were observed in both HEK293 and ARPE cells. After subretinal injection in mice, the average CFI expression in retinal tissue was 266.1 ng/ml, and serum CFI expression averaged 27.2 ng/ml. Meanwhile, the average intraocular C3 content decreased from a baseline of 121.78 μg/ml to 98.03 μg/ml.

Conclusions : Subretinal injection delivery of the AAV-CB-hCFI vector proves to be an efficient method. Data suggest that CFI expression can effectively reduce complement C3 level, making it a potential therapeutic target for treating dry AMD.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.