AAV8-vectored suprachoroidal gene transfer produces widespread ocular transgene expression

Abstract

There has been great progress in ocular gene therapy, but delivery of viral vectors to the retinal pigmented epithelium (RPE) and retina can be challenging. Subretinal injection, the preferred route of delivery for most applications, requires a surgical procedure that has risks. Herein we report a novel gene therapy delivery approach, suprachoroidal injection of AAV8 vectors, which is less invasive and could be done in an outpatient setting. Two weeks after suprachoroidal injection of AAV8.GFP in rats, GFP fluorescence covered 18.9% of RPE flat mounts and extended entirely around sagittal and transverse sections in RPE and photoreceptors. After 2 suprachoroidal injections of AAV8.GFP, GFP fluorescence covered 30.5% of RPE flat mounts. Similarly, widespread expression of GFP occurred in nonhuman primate and pig eyes after suprachoroidal injection of AAV8. GFP. Compared with subretinal injection in rats of RGX-314, an AAV8 vector expressing an anti-VEGF Fab, suprachoroidal injection of the same dose of RGX-314 resulted in similar expression of anti-VEGF Fab and similar suppression of VEGFinduced vascular leakage. Suprachoroidal AAV8 vector injection provides a noninvasive outpatient procedure to obtain widespread transgene expression in retina and RPE.

Host immune responses after suprachoroidal delivery of AAV8 in nonhuman primate eyes

“…In this study, we evaluated host immune responses to a novel mode of delivering viral vectors into the suprachoroidal space of NHPs using transscleral microneedles. 21,22 Using an AAV8 vector to express GFP under a CMV promoter, we found that suprachoroidal delivery can trigger a peripheral chorioretinitis and vitritis with outer retinal disruption at month 1 after viral injection, but subsequently showed resolution of inflammation and restoration of retinal architecture at month 3, after systemic corticosteroid administration. The inflammation was accompanied by both humoral and cell-mediated responses to the GFP transgene product, but a less pronounced humoral response to the AAV8 capsid than intravitreal injections.…”

“…13,20 We and others have recently described a novel mode of ocular gene delivery by injecting AAV into the suprachoroidal space, which is located between the scleral wall and the choroidal vasculature of the eye. 21,22 Although this potential space is barely detectable under physiologic conditions, 23,24 suprachoroidal injection of compounds using transscleral microneedles expands the suprachoroidal space as seen on in vivo imaging, 25,26 enabling targeted drug delivery to retinal and choroidal tissues while minimizing adverse effects on anterior segment structures. [27][28][29][30][31] Suprachoroidal injection of a triamcinolone acetonide suspension using these microneedles has been effective in treating macular edema from noninfectious uveitis in human clinical trials.…”

Suprachoroidal and Subretinal Injections of AAV Using Transscleral Microneedles for Retinal Gene Delivery in Nonhuman Primates

“…55 However, the blood supply to the rabbit retina is merangiotic, while humans and other primates have holangiotic retinal vasculature. A more recent study by Ding et al 56 also demonstrated this approach in Norway brown rats, but the ocular dimensions of the rat eye are much smaller than humans and primates, and the suprachoroidal space is more difficult to access reliably. The team also employed a conventional 27-gauge needle to deliver AAV8 suprachoroidally in three nonhuman primates, 56 but this free-hand technique is less precise and cannot exclude the possibility of inadvertent subretinal delivery.…”

“…A more recent study by Ding et al 56 also demonstrated this approach in Norway brown rats, but the ocular dimensions of the rat eye are much smaller than humans and primates, and the suprachoroidal space is more difficult to access reliably. The team also employed a conventional 27-gauge needle to deliver AAV8 suprachoroidally in three nonhuman primates, 56 but this free-hand technique is less precise and cannot exclude the possibility of inadvertent subretinal delivery. In contrast, our study employed rhesus macaques with ocular dimensions and vasculature similar to humans, and transscleral microneedles, which reliably access the suprachoroidal space with well-characterized biodistribution, 57,58 and are already employed in human patients in phase I/II clinical trials.…”

Suprachoroidal Delivery of Viral and Nonviral Gene Therapy for Retinal Diseases

“…Another method to access the SCS is the free-hand technique using a standard hypodermic needle attached to a Hamilton syringe or insulin syringe. 22 In this method, the needle is inserted directly and tangentially through the sclera behind the limbus with or without sclerotomy. The needle is then slowly advanced with gentle pressure on the plunger, and the injection slowly performed when the loss of resistance is experienced.…”