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Castro BFM, Steel JC, Layton CJ. AAV-Based Strategies for Treatment of Retinal and Choroidal Vascular Diseases: Advances in Age-Related Macular Degeneration and Diabetic Retinopathy Therapies. BioDrugs 2024; 38:73-93. [PMID: 37878215 PMCID: PMC10789843 DOI: 10.1007/s40259-023-00629-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2023] [Indexed: 10/26/2023]
Abstract
Age-related macular degeneration (AMD) and diabetic retinopathy (DR) are vascular diseases with high prevalence, ranking among the leading causes of blindness and vision loss worldwide. Despite being effective, current treatments for AMD and DR are burdensome for patients and clinicians, resulting in suboptimal compliance and real risk of vision loss. Thus, there is an unmet need for long-lasting alternatives with improved safety and efficacy. Adeno-associated virus (AAV) is the leading vector for ocular gene delivery, given its ability to enable long-term expression while eliciting relatively mild immune responses. Progress has been made in AAV-based gene therapies for not only inherited retinal diseases but also acquired conditions with preclinical and clinical studies of AMD and DR showing promising results. These studies have explored several pathways involved in the disease pathogenesis, as well as different strategies to optimise gene delivery. These include engineered capsids with enhanced tropism to particular cell types, and expression cassettes incorporating elements for a targeted and controlled expression. Multiple-acting constructs have also been investigated, in addition to gene silencing and editing. Here, we provide an overview of strategies employing AAV-mediated gene delivery to treat AMD and DR. We discuss preclinical efficacy studies and present the latest data from clinical trials for both diseases.
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Affiliation(s)
- Brenda F M Castro
- LVF Ophthalmology Research Centre, Translational Research Institute, Brisbane, QLD, 4102, Australia.
- Greenslopes Clinical School, University of Queensland School of Medicine, Brisbane, QLD, Australia.
| | - Jason C Steel
- LVF Ophthalmology Research Centre, Translational Research Institute, Brisbane, QLD, 4102, Australia
- Greenslopes Clinical School, University of Queensland School of Medicine, Brisbane, QLD, Australia
- School of Health, Medical and Applied Sciences, Central Queensland University, Rockhampton, QLD, Australia
| | - Christopher J Layton
- LVF Ophthalmology Research Centre, Translational Research Institute, Brisbane, QLD, 4102, Australia.
- Greenslopes Clinical School, University of Queensland School of Medicine, Brisbane, QLD, Australia.
- School of Health, Medical and Applied Sciences, Central Queensland University, Rockhampton, QLD, Australia.
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Ross M, Obolensky A, Averbukh E, Desrosiers M, Ezra-Elia R, Honig H, Yamin E, Rosov A, Dvir H, Gootwine E, Banin E, Dalkara D, Ofri R. Outer retinal transduction by AAV2-7m8 following intravitreal injection in a sheep model of CNGA3 achromatopsia. Gene Ther 2022; 29:624-635. [PMID: 34853444 DOI: 10.1038/s41434-021-00306-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 10/26/2021] [Accepted: 11/15/2021] [Indexed: 01/09/2023]
Abstract
Sheep carrying a mutated CNGA3 gene exhibit diminished cone function and provide a naturally occurring large animal model of achromatopsia. Subretinal injection of a vector carrying the CNGA3 transgene resulted in long-term recovery of cone function and photopic vision in these sheep. Research is underway to develop efficacious vectors that would enable safer transgene delivery, while avoiding potential drawbacks of subretinal injections. The current study evaluated two modified vectors, adeno-associated virus 2-7m8 (AAV2-7m8) and AAV9-7m8. Intravitreal injection of AAV2-7m8 carrying enhanced green fluorescent protein under a cone-specific promoter resulted in moderate photoreceptor transduction in wild-type sheep, whereas peripheral subretinal delivery of AAV9-7m8 resulted in the radial spread of the vector beyond the point of deposition. Intravitreal injection of AAV2-7m8 carrying human CNGA3 in mutant sheep resulted in mild photoreceptor transduction, but did not lead to the clinical rescue of photopic vision, while day-blind sheep treated with a subretinal injection exhibited functional recovery of photopic vision. Transgene messenger RNA levels in retinas of intravitreally treated eyes amounted to 4-23% of the endogenous CNGA3 levels, indicating that expression levels >23% are needed to achieve clinical rescue. Overall, our results indicate intravitreal injections of AAV2.7m8 transduce ovine photoreceptors, but not with sufficient efficacy to achieve clinical rescue in CNGA3 mutant sheep.
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Affiliation(s)
- M Ross
- Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot, Israel
| | - A Obolensky
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - E Averbukh
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - M Desrosiers
- Department of Therapeutics, Institut de la Vision, Paris, France
| | - R Ezra-Elia
- Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot, Israel
| | - H Honig
- Department of Animal Science, ARO, The Volcani Center, Rishon LeZion, Israel
| | - E Yamin
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - A Rosov
- Department of Animal Science, ARO, The Volcani Center, Rishon LeZion, Israel
| | - H Dvir
- Department of Animal Science, ARO, The Volcani Center, Rishon LeZion, Israel
| | - E Gootwine
- Department of Animal Science, ARO, The Volcani Center, Rishon LeZion, Israel
| | - E Banin
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - D Dalkara
- Department of Therapeutics, Institut de la Vision, Paris, France
| | - R Ofri
- Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot, Israel.
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Systemic and local immune responses to intraocular AAV vector administration in non-human primates. Mol Ther Methods Clin Dev 2022; 24:306-316. [PMID: 35229004 PMCID: PMC8844404 DOI: 10.1016/j.omtm.2022.01.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 01/20/2022] [Indexed: 12/12/2022]
Abstract
Positive clinical outcomes in adeno-associated virus (AAV)-mediated retinal gene therapy have often been attributed to the low immunogenicity of AAVs and immune privilege of the eye. However, several recent studies have shown potential for inflammatory responses. The current understanding of the factors contributing to inflammation, such as the pre-existence of serum antibodies against AAVs and their contribution to increases in antibody levels post-injection, is incomplete. The parameters that regulate the generation of new antibodies in response to the AAV capsid or transgene after intraocular injections are also insufficiently described. This study is a retrospective analysis of the pre-existing serum antibodies in correlation with changes in antibody levels after intraocular injections of AAV in non-human primates (NHPs) of the species Macaca fascicularis. In NHP serums, we analyzed the binding antibody (BAB) levels and a subset of these called neutralizing antibodies (NABs) that impede AAV transduction. We observed significantly higher pre-existing serum BABs against AAV8 compared with other serotypes and a dose-dependent increase in BABs and NABs in the serums collected post-injection, irrespective of the serotype or the mode of injection. Lastly, we were able to demonstrate a correlation between the serum BAB levels with clinical grading of inflammation and levels of transgene expression.
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Ross M, Ofri R. The future of retinal gene therapy: evolving from subretinal to intravitreal vector delivery. Neural Regen Res 2021; 16:1751-1759. [PMID: 33510064 PMCID: PMC8328774 DOI: 10.4103/1673-5374.306063] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/26/2020] [Accepted: 12/09/2020] [Indexed: 12/18/2022] Open
Abstract
Inherited retinal degenerations are a leading and untreatbale cause of blindness, and as such they are targets for gene therapy. Numerous gene therapy treatments have progressed from laboratory research to clinical trails, and a pioneering gene therapy received the first ever FDA approval for treating patients. However, currently retinal gene therapy mostly involves subretinal injection of the therapeutic agent, which treats a limited area, entails retinal detachment and other potential complications, and requires general anesthesia with consequent risks, costs and prolonged recovery. Therefore there is great impetus to develop safer, less invasive and cheapter methods of gene delivery. A promising method is intravitreal injection, that does not cause retinal detachment, can lead to pan-retinal transduction and can be performed under local anesthesia in out-patient clinics. Intravitreally-injected vectors face several obstacles. First, the vector is diluted by the vitreous and has to overcome a long diffusion distance to the target cells. Second, the vector is exposed to the host's immune response, risking neutralization by pre-existing antibodies and triggering a stronger immune response to the injection. Third, the vector has to cross the inner limiting membrane which is both a physical and a biological barrier as it contains binding sites that could cause the vector's sequestration. Finally, in the target cell the vector is prone to proteasome degradation before delivering the transgene to the nucleus. Strategies to overcome these obstacles include modifications of the viral capsid, through rational design or directed evolution, which allow resistance to the immune system, enhancement of penetration through the inner limiting membrane or reduced degradation by intracellular proteasomes. Furthermore, physical and chemical manipulations of the inner limiting membrane and vitreous aim to improve vector penetration. Finally, compact non-viral vectors that can overcome the immunological, physical and anatomical and barriers have been developed. This paper reviews ongoing efforts to develop novel, safe and efficacious methods for intravitreal delivery of therapeutic genes for inherited retinal degenerations. To date, the most promising results are achieved in rodents with robust, pan-retinal transduction following intravitreal delivery. Trials in larger animal models demonstrate transduction mostly of inner retinal layers. Despite ongoing efforts, currently no intravitreally-injected vector has demonstrated outer retinal transduction efficacy comparable to that of subretinal delivery. Further work is warranted to test promising new viral and non-viral vectors on large animal models of inherited retinal degenerations. Positive results will pave the way to development of the next generation of treatments for inherited retinal degeneration.
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Affiliation(s)
- Maya Ross
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Ron Ofri
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
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Breaking the sound barrier: Towards next-generation AAV vectors for gene therapy of hearing disorders. Hear Res 2020; 413:108092. [PMID: 33268240 DOI: 10.1016/j.heares.2020.108092] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 09/14/2020] [Accepted: 10/08/2020] [Indexed: 12/20/2022]
Abstract
Owing to the advances in transgenic animal technology and the advent of the next-generation sequencing era, over 120 genes causing hereditary hearing loss have been identified by now. In parallel, the field of human gene therapy continues to make exciting and rapid progress, culminating in the recent approval of several ex vivo and in vivo applications. Despite these encouraging developments and the growing interest in causative treatments for hearing disorders, gene therapeutic interventions in the inner ear remain in their infancy and await clinical translation. This review focuses on the adeno-associated virus (AAV), which nowadays represents one of the safest and most promising vectors in gene therapy. We first provide an overview of AAV biology and outline the principles of therapeutic gene transfer with recombinant AAV vectors, before pointing out major challenges and solutions for clinical translation including vector manufacturing and species translatability. Finally, we highlight seminal technologies for engineering and selection of next-generation "designer" AAV capsids, and illustrate their power and potential with recent examples of their application for inner ear gene transfer in animals.
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Abstract
Adeno-associated virus (AAV) has emerged as the vector of choice for delivering genes to the mammalian retina. From the first gene therapy to receive FDA approval for the inherited retinal disease (Luxturna™) to more recent clinical trials using microbial opsins to regain light sensitivity, therapeutic transgenes rely on AAV vectors for safe and efficient gene delivery to retinal cells. Such vectors are administered to the retina via subretinal (SR) injection or intravitreal (IVT) injection routes depending on the targeted retinal cell type. An attractive target for gene therapy is the fovea, bearing the highest concentration of cone cells responsible for our high acuity daylight vision. However, previous clinical trials and large animal studies reported that SR administration of vector under the cone-exclusive fovea disrupts its fine structure and might impair visual acuity. Due to its technical difficulty and potential risks, alternatives to vector injection under this delicate region have been investigated by using novel AAV capsid variants identified via rational design or directed evolution. We recently established new vector-promoter combinations to overcome the limitations associated with AAV-mediated cone transduction in the fovea. Our methods provide efficient foveal cone transduction without detaching this delicate region and rely on the use of engineered AAVs and optimal promoters compatible with optogenetic vision restoration. Here we describe in detail our AAV vectors, methods for intravitreal and subretinal injections as well as pre- and postoperative procedures as performed in cynomolgus macaques.
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Ross M, Obolensky A, Averbukh E, Ezra-Elia R, Yamin E, Honig H, Dvir H, Rosov A, Hauswirth WW, Gootwine E, Banin E, Ofri R. Evaluation of Photoreceptor Transduction Efficacy of Capsid-Modified Adeno-Associated Viral Vectors Following Intravitreal and Subretinal Delivery in Sheep. Hum Gene Ther 2020; 31:719-729. [PMID: 32486858 DOI: 10.1089/hum.2020.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Gene augmentation therapy based on subretinal delivery of adeno-associated viral (AAV) vectors is proving to be highly efficient in treating several inherited retinal degenerations. However, due to potential complications and drawbacks posed by subretinal injections, there is a great impetus to find alternative methods of delivering the desired genetic inserts to the retina. One such method is an intravitreal delivery of the vector. Our aim was to evaluate the efficacy of two capsid-modified vectors that are less susceptible to cellular degradation, AAV8 (doubleY-F) and AAV2 (quadY-F+T-V), as well as a third, chimeric vector AAV[max], to transduce photoreceptor cells following intravitreal injection in sheep. We further tested whether saturation of inner limiting membrane (ILM) viral binding sites using a nonmodified vector, before the intravitreal injection, would enhance the efficacy of photoreceptor transduction. Only AAV[max] resulted in moderate photoreceptor transduction following intravitreal injection. Intravitreal injection of the two other vectors did not result in photoreceptor transduction nor did the saturation of the ILM before the intravitreal injection. However, two of the vectors efficiently transduced photoreceptor cells following subretinal injection in positive control eyes. Previous trials with the same vectors in both murine and canine models resulted in robust and moderate transduction efficacy, respectively, of photoreceptors following intravitreal delivery, demonstrating the importance of utilizing as many animal models as possible when evaluating new strategies for retinal gene therapy. The successful photoreceptor transduction of AAV[max] injected intravitreally makes it a potential candidate for intravitreal delivery, but further trials are warranted to determine whether the transduction efficacy is sufficient for a clinical outcome.
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Affiliation(s)
- Maya Ross
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Alexey Obolensky
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Edward Averbukh
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Raaya Ezra-Elia
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Esther Yamin
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Hen Honig
- Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Hay Dvir
- Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Alexander Rosov
- Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - William W Hauswirth
- Department of Ophthalmology, University of Florida, Gainesville, Florida, USA
| | - Elisha Gootwine
- Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Eyal Banin
- Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Ron Ofri
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
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Kansara V, Muya L, Wan CR, Ciulla TA. Suprachoroidal Delivery of Viral and Nonviral Gene Therapy for Retinal Diseases. J Ocul Pharmacol Ther 2020; 36:384-392. [PMID: 32255727 PMCID: PMC7404827 DOI: 10.1089/jop.2019.0126] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Retinal gene therapy is a rapidly growing field with numerous clinical trials underway, and route of delivery is a critical contributor to its success. Subretinal administration, which involves pars plana vitrectomy in the operating room, offers targeted delivery to retinal-pigment epithelium cells and photoreceptors. Due to the immune-privileged nature of the subretinal space, the risk of an immune reaction against viral capsid antigens is minimized, an advantage of subretinal administration in patients with preexisting neutralizing antibodies. Intravitreal administration, with fewer procedure-related complications, is challenged by potential immune response and incomplete vector penetration through the internal limiting membrane. However, novel vectors, optimized by "directed evolution" may address these issues. Nonsurgical in-office suprachoroidal gene delivery offers the potential for greater surface-area coverage of the posterior segment compared to focal subretinal injection, and is not hindered by the internal limiting membrane. However, the vector must pass through multiple layers to reach the targeted retinal layers, and there is a risk of immune response. This review highlights recent developments, challenges, and future opportunities associated with viral and nonviral suprachoroidal gene delivery for the treatment of chorioretinal diseases. While ocular tolerability and short-term effectiveness of suprachoroidal gene delivery have been demonstrated in preclinical models, durability of gene expression, long-term safety, potential systemic exposure, and effective delivery to the macula require further exploration. Although the safety and efficacy of suprachoroidal gene delivery are yet to be proven in clinical trials, further optimization could facilitate nonsurgical in-office suprachoroidal gene therapy.
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Affiliation(s)
| | - Leroy Muya
- Clearside Biomedical, Inc., Alpharetta, Georgia
| | | | - Thomas A. Ciulla
- Clearside Biomedical, Inc., Alpharetta, Georgia
- Address correspondence to: Dr. Thomas A. Ciulla, Clearside Biomedical, Inc., 900 Northpoint Parkway Suite 200, Alpharetta, GA 30005
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Gamlin PD, Alexander JJ, Boye SL, Witherspoon CD, Boye SE. SubILM Injection of AAV for Gene Delivery to the Retina. Methods Mol Biol 2019; 1950:249-262. [PMID: 30783978 PMCID: PMC6700748 DOI: 10.1007/978-1-4939-9139-6_14] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Adeno-associated virus (AAV) has emerged as the vector of choice for delivering genes to the retina. Indeed, the first gene therapy to receive FDA approval in the United States is an AAV-based treatment for the inherited retinal disease, Leber congenital amaurosis-2. Voretigene neparvovec (Luxturna™) is delivered to patients via subretinal (SR) injection, an invasive surgical procedure that requires detachment of photoreceptors (PRs) from the retinal pigment epithelium (RPE). It has been reported that subretinal administration of vector under the cone-exclusive fovea leads to a loss of central retinal structure and visual acuity in some patients. Due to its technical difficulty and potential risks, alternatives to SR injection have been explored in primates. Intravitreally (Ivt) delivered AAV transduces inner retina and foveal cones, but with low efficiency. Novel AAV capsid variants identified via rational design or directed evolution have offered only incremental improvements, and have failed to promote pan-inner retinal transduction or significant outer retinal transduction beyond the fovea. Problems with retinal transduction by Ivt-delivered AAV include dilution in the vitreous, potential antibody-mediated neutralization of capsid in this nonimmune privileged space, and the presence of the inner limiting membrane (ILM), a basement membrane separating the vitreous from the neural retina. We have developed an alternative "subILM" injection method that overcomes all three hurdles. Specifically, vector is placed in a surgically induced, hydrodissected space between the ILM and neural retina. We have shown that subILM injection promotes more efficient retinal transduction by AAV than Ivt injection, and results in uniform and extensive transduction of retinal ganglion cells (RGCs) beneath the subILM bleb. We have also demonstrated transduction of Muller glia, ON bipolar cells, and photoreceptors by subILM injection. Our results confirm that the ILM is a major barrier to transduction by AAV in primate retina and that, when it is circumvented, the efficiency and depth to which AAV2 promotes transduction of multiple retinal cell classes is greatly enhanced. Here we describe in detail methods for vector preparation, vector dilution, and subILM injection as performed in macaque (Macaca sp.).
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Affiliation(s)
- Paul D Gamlin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - John J Alexander
- Department of Human Genetics, Emory University, Atlanta, GA, USA
| | - Sanford L Boye
- Department of Pediatrics and the Powell Gene Therapy Center, University of Florida College of Medicine, Gainesville, FL, USA
| | - C Douglas Witherspoon
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Shannon E Boye
- Department of Ophthalmology, University of Florida College of Medicine, Gainesville, FL, USA
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