Bartoe, J. T. | bioRxiv Science

bioRxiv2022

Injectable polymer-nanoparticle hydrogel for the sustained intravitreal delivery of bimatoprost

Vision impairment resulting from chronic eye diseases, such as macular degeneration and glaucoma, severely impacts patients quality of life and poses an immense global financial burden. Current standard of care for such diseases includes daily eye drops or frequent intravitreal (ITV) injections, which are burdensome treatment modalities resulting in low patient compliance. There remains a growing need for easily administered long-acting delivery technologies for prolonging exposure of ocular therapeutics with each administration. Here, we deploy a supramolecular polymer-nanoparticle (PNP) hydrogel for ITV delivery of the glaucoma drug bimatoprost. PNP hydrogels are shear-thinning and self-healing, key properties for injectability, and enable slow release of molecular cargo in vitreous humor (VH) mimics. An in vivo study in New Zealand white rabbits demonstrated intravitreally injected PNP hydrogels form depots that degrade slowly over time, maintaining detectable levels of bimatoprost in the VH up to eight weeks following injection. Ophthalmic examinations and histopathology identified a mild foreign body response (FBR) to the hydrogel, characterized by rare clusters of foamy macrophages and giant cells associated with minimal, patchy fibroplasia. This work shows that PNP hydrogels exhibit numerous desirable traits for sustained drug delivery and further work will be necessary to optimize tolerability in the eye.

bioengineering↗

bioRxiv2021

Targeting ON-bipolar cells by AAV gene therapy stably reverses LRIT3-congenital stationary night blindness

AAV gene therapies aimed at curing inherited retinal diseases to date have typically focused on photoreceptors and retinal pigmented epithelia within the relatively accessible outer retina. However, therapeutic targeting in diseases such as congenital stationary night blindness (CSNB) that involve defects in ON-bipolar cells (ON-BCs) within the mid-retina has been challenged by the relative inaccessibility of the target cell in intact retinas, the limited transduction efficiency of these cells by existing AAV serotypes, poor availability of established ON-BC-specific promoters, and absence of appropriate patient-relevant large animal models. Here, we demonstrate safe and effective ON-BC targeting by AAV gene therapy in a recently characterized naturally-occurring canine model of CSNB, LRIT3-CSNB. To effectively target ON-BCs, new AAV capsid variants with ON-BC tropism and ON-BC specific modified GRM6 promoters were adopted to ensure cell-specific transgene expression. Notably, subretinal injection of one vector, AAVK9#4-shGRM6-cLRIT3-WPRE, significantly recovered rod-derived b-wave in all treated eyes (6/6) of adult dogs injected at 1-3 years of age. The robust therapeutic effect was evident 7 weeks post-injection and was sustained for at least 1 year in all treated eyes. Scotopic vision was significantly improved in treated eyes based on visually-guided obstacle course navigation. Restoration of LRIT3 signals was confirmed by immunohistochemistry. Thus, we report on the first ON-BC functional rescue in a large animal model using a novel AAV capsid variant and modified promoter construct optimized for ON-BC specificity, thereby establishing both proof-of-concept and a novel translational platform for treatment of CSNB in patients with defects in photoreceptor-to-bipolar signaling. SignificanceCanine models of inherited retinal diseases have informed and advanced AAV gene therapies targeting specific cells, including photoreceptors in the outer retina, for treatment of blinding diseases in human patients. However, therapeutic targeting of diseases such as congenital stationary night blindness (CSNB) that exhibit defects in ON-bipolar cells (ON-BCs) of the mid-retina remains under-developed. Using a new LRIT3 mutant canine model of CSNB exhibiting ON-BC dysfunction, we tested the ability of a cell-specific AAV capsid and promotor to specifically target ON-BCs for gene delivery. Notably, subretinal injection of AAV-LRIT3 vector demonstrated safety and efficacy with robust and stable rescue of ERG signals and night vision up to 1 year, paving the way for clinical trials in CNSB patients.

neuroscience↗