A Cationic Block Co-Polymer for Gene Delivery in the Posterior Segment of the Eye

Diseases of the back of the eye such as neovascular age-related macular degeneration (nAMD) are vision threatening and treatment is burdensome for patients, often requiring ocular injections every other month. Injection risks and logistics lower patient compliance; however, even patients receiving optimal treatment can deteriorate. Gene silencing has shown great potential as a therapeutic alternative but is often limited by instability of the genetic payload, reducing efficacy. In the current work, a cationic block co-polymer was developed and investigated as a delivery system for an antisense oligonucleotide (ASO) to the posterior segment of the eye. This work details the synthesis, characterization, in vitro, and ex vivo testing of the polymer and the subsequent polyplexes formed between the polymer and ASO. pH-dependent polyplexes were formed which fully complexed the ASO at 1:1 and 10:1 ratios of polymer amine groups to ASO phosphate groups (N/P ratio). Neither formulation displayed a significant reduction in the viability of human retinal pigment epithelial (ARPE-19) cells. The polyplexes were under 150 nm in diameter, with a slightly negative zeta potential. In comparison to the naked ASO, the 10:1 polyplexes achieved superior transfection into ARPE-19 cells. After 24 h, the ASO delivered by the 10:1 polyplexes displayed significant knockdown of the target protein. Polyplexes were well distributed throughout the vitreous humor, retina, and choroid within 4 h of intravitreal administration in an ex vivo porcine eye. These materials show potential for gene delivery in the treatment of various posterior segment conditions including nAMD.