“Para-retinal” Vector Administration into the Deep Vitreous Enhances Retinal Transgene Expression

Yong Zeng,Ryan Boyd,Joshua Bartoe,Henry E Wiley,Dario Marangoni,Lisa L Wei,Paul A Sieving

doi:10.1016/j.omtm.2020.06.015

Abstract

Intravitreal administration for human adeno-associated vector (AAV) delivery is easier and less traumatic to ocular tissues than subretinal injection, but it gives limited retinal transduction. AAV vectors are large (about 4,000 kDa) compared with most intraocular drugs, such as ranibizumab (48 kDa), and the large size impedes diffusion to reach the retina from the usual injection site in the anterior/mid-vitreous. Intuitively, a preferred placement for the vector would be deep in the vitreous near the retina, which we term “para-retinal” delivery. We explored the consequences of para-retinal intravitreal delivery in the rabbit eye and in non-human primate (NHP) eye. 1 h after para-retinal administration in the rabbit eye, the vector concentration near the retina remained four times greater than in the anterior vitreous, indicating limited vector diffusion through the gelatinous vitreous matrix. In NHP, para-retinal placement showed greater transduction in the fovea than vector applied in the mid-vitreous. More efficient retinal delivery translates to using lower vector doses, with reduced risk of ocular inflammatory exposure. These results indicate that para-retinal delivery yields more effective vector concentration near the retina, thereby increasing the potential for better retinal transduction in human clinical application.

Highlights

The eye is advantageous for exploring gene therapy, as the small closed compartment requires minimal vector quantity and is somewhat protected against immune system activation.[1]
Two non-human primate (NHP) eyes were dosed by para-retinal application, a third was dosed by standard mid-vitreous injection, and a fourth received excipient as a control
Results of Para-retinal Delivery into Rabbit Eyes The rabbit study assessed whether para-retinal delivery of AAV8CMV-EGFP vector gave higher local concentration that persisted temporarily in the posterior vitreous compared to the anterior vitreous near the lens

Summary

Introduction

The eye is advantageous for exploring gene therapy, as the small closed compartment requires minimal vector quantity and is somewhat protected against immune system activation.[1]. Subretinal application, which is used for voretigene neparvovec-rzyl (Luxterna) has the advantage of placing the vector adjacent to target retina cells, including the photoreceptors and retinal pigment epithelium (RPE), which frequently are affected by retinal diseases. Subretinal administration requires surgical manipulation of retinal tissue, and vector distribution is limited to the region near the injection site.[2] The procedure itself requires local retinal detachment of photoreceptors from the RPE, which may cause immediate or lasting retinal damage.[2] Intravitreal application is minimally traumatic and can reach a larger expanse of the retina, as used for the Gensight LHON vector, which targets retinal ganglion cells and axons at the retina surface. Standard intravitreal application yields poor transduction efficiency for reaching the photoreceptors and RPE.[3]

Methods

Results

Conclusion