Gene therapy for neovascular age-related macular degeneration: rationale, clinical trials and future directions

Phase 1/2 AAV5-hRKp.RPGR (Botaretigene Sparoparvovec) Gene Therapy: Safety and Efficacy in RPGR-associated X-linked Retinitis Pigmentosa

PURPOSE

To assess the safety and efficacy of AAV5-hRKp.RPGR in participants with retinitis pigmentosa GTPase regulator (RPGR)-associated X-linked retinitis pigmentosa (XLRP).

DESIGN

Open-label, phase 1/2 dose escalation/expansion study (NCT03252847).

METHODS

Males (≥5 years old) with XLRP-RPGR were evaluated. In the dose escalation phase, subretinal AAV5-hRKp.RPGR (low: 1.0×1011 vg/ml; intermediate: 2.0×1011 vg/ml; high: 4.0×1011 vg/ml) was administered to the poorer-seeing eye (n = 10). Dose confirmation (intermediate dose) was carried out in 3 pediatric participants. In the dose expansion phase, 36 participants were randomized 1:1:1 to immediate (low or intermediate dose) or deferred (control) treatment. The primary outcome was safety. Secondary efficacy outcomes included static perimetry, microperimetry, vision-guided mobility, best corrected visual acuity, and contrast sensitivity. Safety and efficacy outcomes were assessed for 52 weeks for immediate treatment participants and 26 weeks for control participants.

RESULTS

AAV5-hRKp.RPGR was safe and well tolerated, with no reported dose-limiting events. Most adverse events (AEs) were transient and related to the surgical procedure, resolving without intervention. Two serious AEs were reported with immediate treatment (retinal detachment, uveitis). A third serious AE (increased intraocular pressure) was reported outside the reporting period. All ocular inflammation-related AEs responded to corticosteroids. Treatment with AAV5-hRKp.RPGR resulted in improvements in retinal sensitivity and functional vision compared with the deferred group at Week 26; similar trends were observed at Week 52.

CONCLUSIONS

AAV5-hRKp.RPGR demonstrated an anticipated and manageable AE profile through 52 weeks. Safety and efficacy findings support investigation in a phase 3 trial.

PRDX1 exerts a photoprotection effect by inhibiting oxidative stress and regulating MAPK signaling on retinal pigment epithelium

BACKGROUND

The purpose of this study was to investigate the photoprotection effect of peroxiredoxin 1 (PRDX1) protein in ultraviolet B (UVB) irradiation-induced damage of retinal pigment epithelium (RPE) and its possible molecular mechanism.

METHODS

ARPE-19 cell viability and apoptosis were assessed by MTT assay and flow cytometry, respectively. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect the PRDX1 expression. The corresponding kits were employed to measure the levels or activities of lactate dehydrogenase (LDH), 8-hydroxy-2-deoxyguanosine (8-OHdG), reactive oxygen species (ROS), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD). Western blotting was applied to examine PRDX1 expression and mitogen-activated protein kinase (MAPK) signaling pathway-related proteins.

RESULTS

After exposure to 20 mJ/cm2 intensity of UVB irradiation for 24 h, ARPE-19 cells viability was decreased, the leakage degree of LDH and 8-OHdG were increased, and cell apoptosis was elevated. The expression of PRDX1 was significantly down-regulated in UVB-induced ARPE-19 cells. The low expression of PRDX1 was involved in high irradiation intensity. Overexpression of PRDX1 increased cell activity, decreased cell apoptosis, and LDH as well as 8-OHdG leakage in UVB-induced ARPE-19 cells. In addition to alleviating UVB-induced cell damage, PRDX1 overexpression also inhibited UVB-induced oxidative stress (down-regulation of ROS and MDA levels, up-regulation of GSH-Px and SOD activities) and the activation of MAPK signaling pathway in ARPE-19 cells.

CONCLUSION

PRDX1 exerts a photoprotection effect on RPE by attenuating UVB-induced cell damage and inhibiting oxidative stress, which can be attributed to the inhibition of MAPK signaling pathway activation.

Gene and cell therapy for age-related macular degeneration: A review

Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss among the elderly in Western communities, with an estimated global prevalence of 10 - 20% in people older than 65 years. AMD leads to central vision loss due to degeneration of the photoreceptors, retinal pigment epithelium and the choriocapillaris. Beckman's classification for AMD, based upon color fundus photographs, divides the disease into early, intermediate, and late forms. The late, vision-threatening stage includes both neovascular AMD and geographic atrophy. Despite its high prevalence and impact on patients' quality of life, treatment options for AMD are limited. While neovascular AMD can be medically managed with anti-VEGF intravitreal injections, until very recently there has been no approved treatment options for atrophic AMD; however, in February 2023 the first treatment for geographic atrophy - pegcetacoplan - was approved by the US FDA. We describe the current landscape of potential gene and cell therapeutic strategies for late-stage AMD, with an emphasis on the therapeutic options that might become available in the next few years.

In-Depth Retinal Sensitivity Assessment With the MP3 Type S Microperimeter: A Methods Study

Purpose

Retinal sensitivity is frequently listed as an end point in clinical trials, often with long working practices. The purpose of this methods study was to provide a new workflow and reduced test time for in-depth characterization of retinal sensitivity.

Methods

A workflow for the MP3-S microperimeter with detailed functional characterization of the retina under photopic, mesopic, and scotopic conditions was evaluated. Grids of 32 and 28 test positions for photopic/mesopic and scotopic, respectively, were tested in 12 healthy individuals and compared with an established 68-point grid for test time, mean sensitivity (MS), and bivariate contour ellipse area (BCEA).

Results

The mean test time (range; ±SD) was 10.5 minutes (8.4-14.9; ±2.0) in the 68-point grid and 4.3 minutes (3.8-5.0; ±0.4) in the 32-point grid, which was significantly different (P < 0.0001). The mean of difference in test time (±SD; 95% confidence interval) was 6.1 minutes (±2.0; 4.6-7.6). MS and BCEA were significantly correlated between grids (r = 0.89 and 0.74; P = 0.0005 and 0.014, respectively). Mean test time of subjects who underwent the full protocol (n = 4) was 2.15 hours.

Conclusions

The protocol suggested herein appears highly feasible with in-depth characterization of retinal function under different testing conditions and in a short test time.

Translational Relevance

The protocol described herein allows for characterization of the retina under different testing conditions and in a short test time, which is relevant due to its potential for patient prognostication and follow-up in clinical settings and also given its increasing role as a clinical trial end point.

The contribution of pattern recognition receptor signalling in the development of age related macular degeneration: the role of toll-like-receptors and the NLRP3-inflammasome

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss, characterised by the dysfunction and death of the photoreceptors and retinal pigment epithelium (RPE). Innate immune cell activation and accompanying para-inflammation have been suggested to contribute to the pathogenesis of AMD, although the exact mechanism(s) and signalling pathways remain elusive. Pattern recognition receptors (PRRs) are essential activators of the innate immune system and drivers of para-inflammation. Of these PRRs, the two most prominent are (1) Toll-like receptors (TLR) and (2) NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3)-inflammasome have been found to modulate the progression of AMD. Mutations in TLR2 have been found to be associated with an increased risk of developing AMD. In animal models of AMD, inhibition of TLR and NLRP3 has been shown to reduce RPE cell death, inflammation and angiogenesis signalling, offering potential novel treatments for advanced AMD. Here, we examine the evidence for PRRs, TLRs2/3/4, and NLRP3-inflammasome pathways in macular degeneration pathogenesis.

Advancements in the treatment of age-related macular degeneration: a comprehensive review

Age-related macular degeneration (AMD) stands as a leading cause of irreversible blindness, particularly affecting central vision and impeding daily tasks. This paper provides a thorough exploration of AMD, distinguishing between its two main subtypes-Wet and Dry AMD-while shedding light on the prevalence and risk factors, including age, genetics, and smoking. The focus shifts to the current and future treatment landscape, examining both Dry and Wet AMD. Regarding Dry AMD, interventions such as antioxidant supplementation and ongoing clinical trials offer hope. Notable among these is Pegcetacoplan which is the only Food and Drug Administration (FDA)-approved medication, displaying promising results in reducing geographic atrophy lesions. For Wet AMD, anti-Vascular Endothelial Growth Factor therapies like Ranibizumab (Lucentis®) have been instrumental, and newer drugs like Faricimab and OPT-302 show comparable efficacy with extended dosing intervals. Additionally, gene therapies such as RGX-314 present a potential paradigm shift, reducing or eliminating the need for frequent injections. Biosimilars offer cost-effective alternatives. The paper also delves into the integration of technology and artificial intelligence in AMD management, highlighting the role of smartphone apps for patient monitoring and artificial intelligence algorithms for diagnosis and surveillance. Furthermore, patient perspectives on artificial intelligence demonstrate a positive correlation between understanding and trust. The narrative concludes with a glimpse into ground-breaking technologies, including retinal implants and bionic chips, offering hope for vision restoration. Overall, this paper underscores the multifaceted approach in addressing AMD, combining traditional and innovative strategies, paving the way for a more promising future in AMD treatment.

Age-Related Macular Degeneration and Mitochondria-Associated Autoantibodies: A Review of the Specific Pathogenesis and Therapeutic Strategies

Age-related macular degeneration (AMD) is a severe retinal disease that causes irreversible visual loss and blindness in elderly populations worldwide. The pathological mechanism of AMD is complex, involving the interactions of multiple environmental and genetic factors. A poor understanding of the disease leads to limited treatment options and few effective prevention methods. The discovery of autoantibodies in AMD patients provides an opportunity to explore the pathogenesis and treatment direction of the disease. This review focuses on the mitochondria-associated autoantibodies and summarizes the functional roles of mitochondria under physiological conditions and their alterations during the pathological states. Additionally, it discusses the crosstalk between mitochondria and other organelles, as well as the mitochondria-related therapeutic strategies in AMD.

The suprachoroidal space in patients affected by retinitis pigmentosa

BACKGROUND AND OBJECTIVE

The Suprachoroidal Space (SCS) is a theoretical structure which can be demonstrated between the inner border of the sclera and the outer boundary of the choroid. SCS is being studied for its potential uses as a route for drug delivery and innovative surgical techniques for the treatment of many retinal diseases. Retinitis pigmentosa (RP) is a group of inherited eye disorders characterized by a gradual loss of photoreceptors, resulting in vision impairment, which typically presents as night blindness and progressive visual field loss. The purpose of the study is to define the morphology of outer choroidal margins by means of SS-OCT in RP.

MATERIAL AND METHOD

This is a retrospective observational study designed to evaluate the presence of SCS in RP. We performed Swept Source optical coherence tomography (SS-OCT) in a group of 55 patients affected by RP (26 males and 29 females, 110 eyes) with a mean age of 51.8 ± 13.7 years. In the control group, we included 28 healthy subjects (6 males and 22 females, 56 eyes) with a mean age of 48,8 ± 16,6 years.

RESULTS

OCT scans allowed the outer choroidal margin and inner scleral margin to be delineated with certainty in all 110 eyes. In the RP group SCS was detected in 47 of 110 eyes (42,7%), in the control group SCS was detected in 11 eyes (19,6%). Subjects with SCS visible (RP group) had reduced retinal thickness (168.4 µm) compared to those with not visible SCL (211.2 µm, P = .007).

CONCLUSIONS

SS-OCT can be successfully applied to assess the presence of SCS in RP and the high rate of SCS found in the RP patients is encouraging when considering future innovative therapies.

Recent Developments in Gene Therapy for Neovascular Age-Related Macular Degeneration: A Review

Age-related macular degeneration (AMD) is a complex and multifactorial disease and a leading cause of irreversible blindness in the elderly population. The anti-vascular endothelial growth factor (anti-VEGF) therapy has revolutionized the management and prognosis of neovascular AMD (nAMD) and is currently the standard of care for this disease. However, patients are required to receive repeated injections, imposing substantial social and economic burdens. The implementation of gene therapy methods to achieve sustained delivery of various therapeutic proteins holds the promise of a single treatment that could ameliorate the treatment challenges associated with chronic intravitreal therapy, and potentially improve visual outcomes. Several early-phase trials are currently underway, evaluating the safety and efficacy of gene therapy for nAMD; however, areas of controversy persist, including the therapeutic target, route of administration, and potential safety issues. In this review, we assess the evolution of gene therapy for nAMD and summarize several preclinical and early-stage clinical trials, exploring challenges and future directions.

Chimpanzee adenovirus-mediated multiple gene therapy for age-related macular degeneration

Neovascular age-related macular degeneration AMD (nAMD) is characterized by choroidal neovascularization (CNV) and could lead to irreversible blindness. However, anti-vascular endothelial growth factor (VEGF) therapy has limited efficacy. Therefore, we generated a chimpanzee adenoviral vector (AdC68-PFC) containing three genes, pigment endothelial-derived factor (PEDF), soluble fms-like tyrosine kinase-1 (sFlt-1), and soluble forms of CD59 (sCD59), to treat nAMD. The results showed that AdC68-PFC mediated a strong onset of PEDF, sFlt-1, and sCD59 expression both in vivo and in vitro. AdC68-PFC showed preventive and therapeutic effects following intravitreal (IVT) injection in the laser-induced CNV model and very low-density lipoprotein receptor-deficient (Vldlr-/-) mouse model. In vitro assessment indicated that AdC68-PFC had a strong inhibitory effect on endothelial cells. Importantly, the safety test showed no evidence of in vivo toxicity of adenovirus in murine eyes. Our findings suggest that AdC68-PFC may be a long-acting and safe gene therapy vector for future nAMD treatments.

Design Parameters for Injectable Biopolymeric Hydrogels with Dynamic Covalent Chemistry Crosslinks

Dynamic covalent chemistry (DCC) crosslinks can form hydrogels with tunable mechanical properties permissive to injectability and self-healing. However, not all hydrogels with transient crosslinks are easily extrudable. For this reason, two additional design parameters must be considered when formulating DCC-crosslinked hydrogels: 1) degree of functionalization (DoF) and 2) polymer molecular weight (MW). To investigate these parameters, hydrogels comprised of two recombinant biopolymers: 1) a hyaluronic acid (HA) modified with benzaldehyde and 2) an elastin-like protein (ELP) modified with hydrazine (ELP-HYD), are formulated. Several hydrogel families are synthesized with distinct HA MW and DoF while keeping the ELP-HYD component constant. The resulting hydrogels have a range of stiffnesses, G' ≈ 10-1000 Pa, and extrudability, which is attributed to the combined effects of DCC crosslinks and polymer entanglements. In general, lower MW formulations require lower forces for injectability, regardless of stiffness. Higher DoF formulations exhibit more rapid self-healing. Gel extrusion through a cannula (2 m length, 0.25 mm diameter) demonstrates the potential for minimally invasive delivery for future biomedical applications. In summary, this work highlights additional parameters that influence the injectability and network formation of DCC-crosslinked hydrogels and aims to guide future design of injectable hydrogels.

Faricimab: Transforming the Future of Macular Diseases Treatment - A Comprehensive Review of Clinical Studies

Degenerative eye conditions such as age-related macular degeneration (AMD), diabetic retinopathy, and retinal vein occlusion are major contributors to significant vision loss in developed nations. The primary therapeutic approach for managing complications linked to these diseases involves the intravitreal delivery of anti-vascular endothelial growth factor (VEGF) treatments. Faricimab is a novel, humanised, bispecific antibody that simultaneously binds all VEGF-A isoforms and Angiopoietin-2, which has been approved by regulatory agencies, such as the US Food and Drug Administration (FDA), the UK Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency (EMA), for the treatment of neovascular AMD and diabetic macular oedema (DMO). Intravitreal faricimab holds the promise of reducing the treatment burden for patients with these conditions by achieving comparable or superior therapeutic outcomes with fewer clinic visits. The scope of faricimab's application includes addressing complex macular conditions such as DMO. This review intends to elucidate the distinctive pharmacological characteristics of faricimab and provide an overview of the key clinical trials and real-world studies that assess its effectiveness and safety in treating degenerative macular diseases.

Lentiviral delivered aflibercept OXB-203 for treatment of neovascular AMD

Neovascular age-related macular degeneration (nAMD) is a leading cause of blindness in the aging population, with vascular endothelial growth factor (VEGF) playing a key role. Treatment with recombinant anti-VEGFs is the current standard of care; however, it is only effective for 1-2 months at a time and requires re-administration. Gene therapy could pave the way for stable, long-term expression of therapeutic anti-VEGF with a single dose, reducing the frequency of treatment and potentially improving clinical outcomes. As such, we have developed OXB-203, a lentiviral-based gene therapy encoding the anti-VEGF protein aflibercept. Aflibercept derived from OXB-203 exhibited comparable in vitro binding characteristics to VEGF as recombinant aflibercept. Furthermore, its biological potency was demonstrated by the equivalent inhibition of VEGF-induced human umbilical vein endothelial cell (HUVEC) proliferation and tubule formation as recombinant aflibercept. In a rat choroidal neovascularization (CNV) model of nAMD, a single subretinal administration of OXB-203 reduced laser-induced CNV lesion areas analogous to an intravitreal bolus of recombinant aflibercept. Finally, in a head-to-head comparative study, aflibercept derived from OXB-203 was shown to be expressed at significantly higher levels in ocular tissues than from an AAV8-aflibercept vector following a single subretinal delivery to rats. These findings support the therapeutic potential of OXB-203 for the management of nAMD.

[Gene therapy in ophthalmology]

In 2017 the gene therapy medication voretigene neparvovec-rzyl was approved by the U.S. Food and Drug Administration (FDA) for retinal gene therapy of hereditary retinal dystrophies caused by mutations in the RPE65 gene. Voretigene neparvovec-rzyl is a gene augmentation therapy using an  adeno-associated virus-based vector to express a healthy copy of the human RPE65 gene in the patient's retinal pigment epithelial (RPE) cells. The success of gene augmentation therapy in RPE65-linked retinal dystrophy encouraged research activities on the concept of gene supplementation to be extended to nongenetic diseases, such as age-related macular degeneration; however, it also showed that the principle of success cannot be easily extended to other retinal dystrophies. This review article presents the most commonly used principles and technologies of gene therapy and provides an overview of the current challenges and limitations. Furthermore, practice-relevant aspects of the indications and the treatment procedure are discussed. Particular attention is paid to the consideration of disease stages, especially with respect to patient's expectations and the evaluation of treatment success.

Progress and prospects of gene therapy in ophthalmology from 2000 to 2022: A bibliometric analysis

Background

Gene therapy is a treatment approach at the genetic level, which brings great advances in many diseases and develops rapidly in recent years. Currently, its mechanism of action is mainly through the replacement of missing or defective genes, or the reduction of harmful gene products. However, the application of gene therapy in ophthalmology remains limited.

Methods

A total of 1143 articles and reviews published in the field of ocular gene therapies were found in the Web of Science Core Collection database and used for the bibliometric analysis. CiteSpace was mainly applied to the network analysis of countries, institutions, keywords, and dual-map overlay of journals. The visual analysis of authors, journals, and references was used by VOSviewer. The geographical distribution of publications was conducted by R language.

Results

The annual publications are increasing in general. Currently, the USA and the UK are two main sources of publications in this field. Switzerland, Denmark, and Finland are the top 3 countries that establish the most cooperation and exchanges with other countries or regions. The most cited and co-cited journal in this field is Investigative Ophthalmology & Visual Science. Gene therapy studies for eye diseases are mainly focused on retinal dysfunctions by the analysis of references, keywords, and counting of original research, including Leber's congenital amaurosis and retinitis pigmentosa.

Conclusion

This study used bibliometrics to analyze overall characteristics and put forward prospects for the future in the field of gene therapy in ophthalmology. Ocular diseases, especially hereditary retinal diseases, will be the major focus of gene therapy in the future.

Collective endpoint of visual acuity and contrast sensitivity function from hierarchical Bayesian joint modeling

Clinical trials typically analyze multiple endpoints for signals of efficacy. To improve signal detection for treatment effects using the high-dimensional data collected in trials, we developed a hierarchical Bayesian joint model (HBJM) to compute a five-dimensional collective endpoint (CE5D) of contrast sensitivity function (CSF) and visual acuity (VA). The HBJM analyzes row-by-row CSF and VA data across multiple conditions, and describes visual functions across a hierarchy of population, individuals, and tests. It generates joint posterior distributions of CE5D that combines CSF (peak gain, peak frequency, and bandwidth) and VA (threshold and range) parameters. The HBJM was applied to an existing dataset of 14 eyes, each tested with the quantitative VA and quantitative CSF procedures in four Bangerter foil conditions. The HBJM recovered strong correlations among CE5D components at all levels. With 15 qVA and 25 qCSF rows, it reduced the variance of the estimated components by 72% on average. Combining signals from VA and CSF and reducing noises, CE5D exhibited significantly higher sensitivity and accuracy in discriminating performance differences between foil conditions at both the group and test levels than the original tests. The HBJM extracts valuable information about covariance of CSF and VA parameters, improves precision of the estimated parameters, and increases the statistical power in detecting vision changes. By combining signals and reducing noise from multiple tests for detecting vision changes, the HBJM framework exhibits potential to increase statistical power for combining multi-modality data in ophthalmic trials.

Rethinking the potential and necessity of drug delivery systems in neovascular age-related macular degeneration therapy

Age-related macular degeneration (AMD) is the predominant threat to human vision and ultimately results in blindness. With the increase in the aging population, it has become a more crucial issue to human health. AMD is a multifactorial disease with the unique feature of uncontrollable angiogenesis during initiation and progression. Although increasing evidence indicates that AMD is largely hereditary, the predominant efficient treatment is antiangiogenesis, which mainly involves VEGF and HIF-α as therapeutic targets. The repeated administration of this treatment over the long term, generally through intravitreal injection, has called for the introduction of long-term drug delivery systems, which are expected to be achieved by biomaterials. However, the clinical results of the port delivery system indicate that the optimization of medical devices toward prolonging the activities of therapeutic biologics in AMD therapy seems more promising. These results indicate that we should rethink the possibility and potential of biomaterials as drug delivery systems in achieving long-term, sustained inhibition of angiogenesis in AMD therapy. In this review, the etiology, categorization, risk factors, pathogenesis, and current clinical treatments of AMD are briefly introduced. Next, the development status of long-term drug delivery systems is discussed, and the drawbacks and shortages of these systems are emphasized. By comprehensively considering the pathological aspect and the recent application of drug delivery systems in AMD therapy, we hope to find a better solution for the further development of long-term therapeutic strategies for AMD.

Ocular therapies with biomacromolecules: From local injection to eyedrop and emerging noninvasive delivery strategies

The last two decades have witnessed a continuously increasing number of biomacromolecules approved for the treatment of ocular diseases. The eye possesses multiple protective mechanisms to resist the invasion of exogenous substances, but meanwhile these physiological defense systems also act as strong barriers, impeding absorption of most biomacromolecules into the eye. As a result, local injections play predominant roles for posterior ocular delivery of biomacromolecules in clinical practice. To achieve safe and convenient application of biomacromolecules, alternative strategies to realize noninvasive intraocular delivery are necessary. Various nanocarriers, novel penetration enhancers and physical strategies have been explored to facilitate delivery of biomacromolecules to both anterior and posterior ocular segments but still suffered difficulties in clinical translation. This review compares the anatomical and physiological characteristics of the eyes from those frequently adopted experimental species and profiles the well-established animal models of ocular diseases. We also summarize the ophthalmic biomacromolecules launched on the market and put emphasis on emerging noninvasive intraocular delivery strategies of peptides, proteins and genes.

Faricimab for the Treatment of Diabetic Macular Edema and Neovascular Age-Related Macular Degeneration

Nowadays; intravitreal anti-vascular endothelial growth factor (VEGF) drugs are considered the first-line therapeutic strategy for treating macular exudative diseases; including wet age-related macular degeneration (w-AMD) and diabetic macular edema (DME). Despite the important clinical achievements obtained by anti-VEGF drugs in the management of w-AMD and DME; some limits still remain; including high treatment burden; the presence of unsatisfactory results in a certain percentage of patients and long-term visual acuity decline due to complications such as macular atrophy and fibrosis. Targeting the angiopoietin/Tie (Ang/Tie) pathway beyond the VEGF pathway may be a possible therapeutic strategy; which may has the potential to solve some of the previous mentioned challenges. Faricimab is a new; bispecific antibody targeting both VEGF-A and the Ang-Tie/pathway. It was approved by FDA and; more recently; by EMA for treating w-AMD and DME. Results from phase III trials TENAYA and LUCERNE (w-AMD) and RHINE and YOSEMITE (DME) have shown the potential of faricimab to maintain clinical efficacy with more prolonged treatment regimens compared to aflibercept (12 or 16 weeks) with a a good safety profile.

Advanced Therapy Medicinal Products for Age-Related Macular Degeneration; Scaffold Fabrication and Delivery Methods

Retinal degenerative diseases such as age-related macular degeneration (AMD) represent a leading cause of blindness, resulting in permanent damage to retinal cells that are essential for maintaining normal vision. Around 12% of people over the age of 65 have some form of retinal degenerative disease. Whilst antibody-based drugs have revolutionised treatment of neovascular AMD, they are only effective at an early stage and cannot prevent eventual progression or allow recovery of previously lost vision. Hence, there is a clear unmet need to find innovative treatment strategies to develop a long-term cure. The replacement of damaged retinal cells is thought to be the best therapeutic strategy for the treatment of patients with retinal degeneration. Advanced therapy medicinal products (ATMPs) are a group of innovative and complex biological products including cell therapy medicinal products, gene therapy medicinal products, and tissue engineered products. Development of ATMPs for the treatment of retinal degeneration diseases has become a fast-growing field of research because it offers the potential to replace damaged retinal cells for long-term treatment of AMD. While gene therapy has shown encouraging results, its effectiveness for treatment of retinal disease may be hampered by the body's response and problems associated with inflammation in the eye. In this mini-review, we focus on describing ATMP approaches including cell- and gene-based therapies for treatment of AMD along with their applications. We also aim to provide a brief overview of biological substitutes, also known as scaffolds, that can be used for delivery of cells to the target tissue and describe biomechanical properties required for optimal delivery. We describe different fabrication methods for preparing cell-scaffolds and explain how the use of artificial intelligence (AI) can aid with the process. We predict that combining AI with 3D bioprinting for 3D cell-scaffold fabrication could potentially revolutionise retinal tissue engineering and open up new opportunities for developing innovative platforms to deliver therapeutic agents to the target tissues.

Enhanced Biosafety of the Sleeping Beauty Transposon System by Using mRNA as Source of Transposase to Efficiently and Stably Transfect Retinal Pigment Epithelial Cells

Neovascular age-related macular degeneration (nvAMD) is characterized by choroidal neovascularization (CNV), which leads to retinal pigment epithelial (RPE) cell and photoreceptor degeneration and blindness if untreated. Since blood vessel growth is mediated by endothelial cell growth factors, including vascular endothelial growth factor (VEGF), treatment consists of repeated, often monthly, intravitreal injections of anti-angiogenic biopharmaceuticals. Frequent injections are costly and present logistic difficulties; therefore, our laboratories are developing a cell-based gene therapy based on autologous RPE cells transfected ex vivo with the pigment epithelium derived factor (PEDF), which is the most potent natural antagonist of VEGF. Gene delivery and long-term expression of the transgene are enabled by the use of the non-viral Sleeping Beauty (SB100X) transposon system that is introduced into the cells by electroporation. The transposase may have a cytotoxic effect and a low risk of remobilization of the transposon if supplied in the form of DNA. Here, we investigated the use of the SB100X transposase delivered as mRNA and showed that ARPE-19 cells as well as primary human RPE cells were successfully transfected with the Venus or the PEDF gene, followed by stable transgene expression. In human RPE cells, secretion of recombinant PEDF could be detected in cell culture up to one year. Non-viral ex vivo transfection using SB100X-mRNA in combination with electroporation increases the biosafety of our gene therapeutic approach to treat nvAMD while ensuring high transfection efficiency and long-term transgene expression in RPE cells.

High-Capacity Mesoporous Silica Nanocarriers of siRNA for Applications in Retinal Delivery

The main cause of subretinal neovascularisation in wet age-related macular degeneration (AMD) is an abnormal expression in the retinal pigment epithelium (RPE) of the vascular endothelial growth factor (VEGF). Current approaches for the treatment of AMD present considerable issues that could be overcome by encapsulating anti-VEGF drugs in suitable nanocarriers, thus providing better penetration, higher retention times, and sustained release. In this work, the ability of large pore mesoporous silica nanoparticles (LP-MSNs) to transport and protect nucleic acid molecules is exploited to develop an innovative LP-MSN-based nanosystem for the topical administration of anti-VEGF siRNA molecules to RPE cells. siRNA is loaded into LP-MSN mesopores, while the external surface of the nanodevices is functionalised with polyethylenimine (PEI) chains that allow the controlled release of siRNA and promote endosomal escape to facilitate cytosolic delivery of the cargo. The successful results obtained for VEGF silencing in ARPE-19 RPE cells demonstrate that the designed nanodevice is suitable as an siRNA transporter.

Factors That Can Prolong Ocular Treatment Duration in Age-Related Macular Degeneration

Intravitreal injections of anti-vascular endothelial growth factor (VEGF) agents are used to treat wet age-related macular degeneration (wAMD); however, they are associated with a considerable treatment burden and poor real-world outcomes. The molecular size and charge of anti-VEGF agents influence drug pharmacokinetics in the vitreous and peak drug efficacy. This article reviews the established and novel strategies to prolong drug action, in the vitreal cavity, and thus reduce dosing frequency. Increased ocular residency can be attained by increasing drug size as with large molecules, such as KSI-301; adding polyethylene glycol to pegcetacoplan (APL-2) or avacincaptad pegol to increase molecular size; or binding to other targets that increase molecular size, such as vitreal albumin in the case of BI-X. Faricimab is a bispecific antibody in which the fragment crystallizable portion is engineered to prolong ocular residency and reduce systemic exposure. Conversely, small VEGF-binding molecules, such as brolucizumab, can be administered at higher clinical doses, with the potential for prolonged clinical activity versus larger molecules. Other important considerations include sustained drug delivery routes, such as the ranibizumab port delivery system or subconjunctival or suprachoroidal injection. More effective and longer-lasting treatments are needed for wAMD to prolong drug action and reduce dosing frequency. Several strategies are under investigation and the prevention of vision loss in patients with AMD or other retinal diseases may be attainable in the near future.

RNA-targeting strategies as a platform for ocular gene therapy

Genetic medicine is offering hope as new therapies are emerging for many previously untreatable diseases. The eye is at the forefront of these advances, as exemplified by the approval of Luxturna® by the United States Food and Drug Administration (US FDA) in 2017 for the treatment of one form of Leber Congenital Amaurosis (LCA), an inherited blindness. Luxturna® was also the first in vivo human gene therapy to gain US FDA approval. Numerous gene therapy clinical trials are ongoing for other eye diseases, and novel delivery systems, discovery of new drug targets and emerging technologies are currently driving the field forward. Targeting RNA, in particular, is an attractive therapeutic strategy for genetic disease that may have safety advantages over alternative approaches by avoiding permanent changes in the genome. In this regard, antisense oligonucleotides (ASO) and RNA interference (RNAi) are the currently popular strategies for developing RNA-targeted therapeutics. Enthusiasm has been further fuelled by the emergence of clustered regularly interspersed short palindromic repeats (CRISPR)-CRISPR associated (Cas) systems that allow targeted manipulation of nucleic acids. RNA-targeting CRISPR-Cas systems now provide a novel way to develop RNA-targeted therapeutics and may provide superior efficiency and specificity to existing technologies. In addition, RNA base editing technologies using CRISPR-Cas and other modalities also enable precise alteration of single nucleotides. In this review, we showcase advances made by RNA-targeting systems for ocular disease, discuss applications of ASO and RNAi technologies, highlight emerging CRISPR-Cas systems and consider the implications of RNA-targeting therapeutics in the development of future drugs to treat eye disease.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

The Need for Artificial Intelligence Based Risk Factor Analysis for Age-Related Macular Degeneration: A Review

In epidemiology, a risk factor is a variable associated with increased disease risk. Understanding the role of risk factors is significant for developing a strategy to improve global health. There is strong evidence that risk factors like smoking, alcohol consumption, previous cataract surgery, age, high-density lipoprotein (HDL) cholesterol, BMI, female gender, and focal hyper-pigmentation are independently associated with age-related macular degeneration (AMD). Currently, in the literature, statistical techniques like logistic regression, multivariable logistic regression, etc., are being used to identify AMD risk factors by employing numerical/categorical data. However, artificial intelligence (AI) techniques have not been used so far in the literature for identifying risk factors for AMD. On the other hand, artificial intelligence (AI) based tools can anticipate when a person is at risk of developing chronic diseases like cancer, dementia, asthma, etc., in providing personalized care. AI-based techniques can employ numerical/categorical and/or image data thus resulting in multimodal data analysis, which provides the need for AI-based tools to be used for risk factor analysis in ophthalmology. This review summarizes the statistical techniques used to identify various risk factors and the higher benefits that AI techniques provide for AMD-related disease prediction. Additional studies are required to review different techniques for risk factor identification for other ophthalmic diseases like glaucoma, diabetic macular edema, retinopathy of prematurity, cataract, and diabetic retinopathy.

Formulation and Evaluation of Polymer-Based Nanoparticles for Intravitreal Gene-Delivery Applications

The advent of the first-ever retinal gene therapy product, involving subretinal administration of a virus-based gene delivery platform, has garnered hope that this state-of-the-art therapeutic modality may benefit a broad spectrum of patients with diverse retinal disorders. On the other hand, clinical studies have revealed limitations of the applied delivery strategy that may restrict its universal use. To this end, intravitreal administration of synthetic gene-delivery platforms, such as polymer-based nanoparticles (PNPs), has emerged as an attractive alternative to the current mainstay. To achieve success, however, it is imperative that synthetic platforms overcome key biological barriers in human eyes encountered following intravitreal administration, including the vitreous gel and inner limiting membrane (ILM). Here, we introduce a series of experiments, from the fabrication of PNPs to a comprehensive evaluation in relevant experimental models, to determine whether PNPs overcome these barriers and efficiently deliver therapeutic gene payloads to retinal cells. We conclude the article by discussing a few important considerations for successful implementation of the strategy. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Preparation and characterization of PNPs Basic Protocol 2: Evaluation of in vitro transfection efficacy Basic Protocol 3: Evaluation of PNP diffusion in vitreous gel Basic Protocol 4: Ex vivo assessment of PNP penetration within vitreoretinal explant culture Basic Protocol 5: Assessment of in vivo transgene expression mediated by intravitreally administered PNPs.

Retinal and Choroidal Neovascularization Antivascular Endothelial Growth Factor Treatments: The Role of Gene Therapy

Neovascularization in ocular vessels causes a major disease burden. The most common causes of choroidal neovascularization (CNV) are age-related macular degeneration and diabetic retinopathy, which are the leading causes of irreversible vision loss in the adult population. Vascular endothelial growth factor (VEGF) is critical for the formation of new vessels and is the main regulator in ocular angiogenesis and vascular permeability through its receptors. Laser therapy and antiangiogenic factors have been used for CNV treatment. Bevacizumab, ranibizumab, and aflibercept are commonly used anti-VEGF agents; however, high costs and the need for frequent intraocular injections are major drawbacks of anti-VEGF drugs. Gene therapy, given the potency of one-time treatment and no need for frequent injections offers the real possibility of such a lasting treatment, with fewer adverse effects and higher patient quality of life. Herein, we reviewed the role of gene therapy in the CNV treatment. In addition, we discuss the advantages and challenges of current treatments compared with gene therapy.

Design, construction and in vivo functional assessment of a hinge truncated sFLT01

Gene therapy for the treatment of ocular neovascularization has reached clinical trial phases. The AAV2-sFLT01 construct was already evaluated in a phase 1 open-label trial administered intravitreally to patients with advanced neovascular age-related macular degeneration. SFLT01 protein functions by binding to VEGF and PlGF molecules and inhibiting their activities simultaneously. It consists of human VEGFR1/Flt-1 (hVEGFR1), a polyglycine linker, and the Fc region of human IgG1. The IgG1 upper hinge region of the sFLT01 molecule makes it vulnerable to radical attacks and prone to causing immune reactions. This study pursued two goals: (i) minimizing the immunogenicity and vulnerability of the molecule by designing a truncated molecule called htsFLT01 (hinge truncated sFLT01) that lacked the IgG1 upper hinge and lacked 2 amino acids from the core hinge region; and (ii) investigating the structural and functional properties of the aforesaid chimeric molecule at different levels (in silico, in vitro, and in vivo). Molecular dynamics simulations and molecular mechanics energies combined with Poisson-Boltzmann and surface area continuum solvation calculations revealed comparable free energy of binding and binding affinity for sFLT01 and htsFLT01 to their cognate ligands. Conditioned media from human retinal pigment epithelial (hRPE) cells that expressed htsFLT01 significantly reduced tube formation in HUVECs. The AAV2-htsFLT01 virus suppressed vascular development in the eyes of newborn mice. The htsFLT01 gene construct is a novel anti-angiogenic tool with promising improvements compared to existing treatments.

Advancements in ocular gene therapy delivery: vectors and subretinal, intravitreal, and suprachoroidal techniques

INTRODUCTION

: Ocular gene therapy represents fertile ground for rapid innovation, with ever-expanding therapeutic strategies, molecular targets, and indications.

AREAS COVERED

: Potential indications for ocular gene therapy have classically focused on inherited retinal disease (IRD), but more recently include acquired retinal diseases, such as neovascular age-related macular degeneration, geographic atrophy and diabetic retinopathy. Ocular gene therapy strategies have proliferated recently, and include gene augmentation, gene inactivation, gene editing, RNA modulation, and gene-independent gene augmentation. Viral vector therapeutic constructs include adeno-associated virus and lentivirus and continue to evolve through directed evolution and rationale design. Ocular gene therapy administration techniques have expanded beyond pars plana vitrectomy with subretinal injection to intravitreal injection and suprachoroidal injection.

EXPERT OPINION

: The success of treatment for IRD, paired with the promise of clinical research in acquired retinal diseases and in administration techniques, has raised the possibility of in-office gene therapy for common retinal disorders within the next five to ten years.

Aflibercept versus Faricimab in the Treatment of Neovascular Age-Related Macular Degeneration and Diabetic Macular Edema: A Review

Diabetic macular edema (DME) and neovascular age-related macular degeneration (nAMD) are common retinal vascular diseases responsible for most blindness in the working-age and older population in developed countries. Currently, anti-VEGF agents that block VEGF family ligands, including ranibizumab, bevacizumab (off-label use), brolucizumab, and aflibercept, are the first-line treatment for nAMD and DME. However, due to the complex pathophysiological background of nAMD and DME, non-response, resistance during anti-VEGF therapy, and relapses of the disease are still observed. Moreover, frequent injections are a psychological and economic burden for patients, leading to inadequate adhesion to therapy and a higher risk of complications. Therefore, therapeutic methods are strongly needed to develop and improve, allowing for more satisfactory disease management and lower treatment burden. Currently, the Ang/Tie-2 pathway is a promising therapeutic target for retinal vascular diseases. Faricimab is the first bispecific monoclonal antibody for intravitreal use that can neutralize VEGF and Ang-2. Due to the prolonged activity, faricimab allows extending the interval between successive injections up to three or four months in nAMD and DME patients, which can be a significant benefit for patients and an alternative to implanted drug delivery systems.

Molecular Genetic Mechanisms in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is among the leading causes of irreversible blindness worldwide. In addition to environmental risk factors, such as tobacco use and diet, genetic background has long been established as a major risk factor for the development of AMD. However, our ability to predict disease risk and personalize treatment remains limited by our nascent understanding of the molecular mechanisms underlying AMD pathogenesis. Research into the molecular genetics of AMD over the past two decades has uncovered 52 independent gene variants and 34 independent loci that are implicated in the development of AMD, accounting for over half of the genetic risk. This research has helped delineate at least five major pathways that may be disrupted in the pathogenesis of AMD: the complement system, extracellular matrix remodeling, lipid metabolism, angiogenesis, and oxidative stress response. This review surveys our current understanding of each of these disease mechanisms, in turn, along with their associated pathogenic gene variants. Continued research into the molecular genetics of AMD holds great promise for the development of precision-targeted, personalized therapies that bring us closer to a cure for this debilitating disease.

Biomarkers as Predictive Factors of Anti-VEGF Response

Age-related macular degeneration is the main cause of irreversible vision in developed countries, and intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections are the current gold standard treatment today. Although anti-VEGF treatment results in important improvements in the course of this disease, there is a considerable number of patients not responding to the standardized protocols. The knowledge of how a patient will respond or how frequently retreatment might be required would be vital in planning treatment schedules, saving both resource utilization and financial costs, but today, there is not an ideal biomarker to use as a predictive response to ranibizumab therapy. Whole blood and blood mononuclear cells are the samples most studied; however, few reports are available on other important biofluid samples for studying this disease, such as aqueous humor. Moreover, the great majority of studies carried out to date were focused on the search for SNPs in genes related to AMD risk factors, but miRNAs, proteomic and metabolomics studies have rarely been conducted in anti-VEGF-treated samples. Here, we propose that genomic, proteomic and/or metabolomic markers could be used not alone but in combination with other methods, such as specific clinic characteristics, to identify patients with a poor response to anti-VEGF treatment to establish patient-specific treatment plans.

Novel and investigational therapies for wet and dry age-related macular degeneration

Age-related macular degeneration (AMD) is a macular degenerative eye disease, the major cause of irreversible loss of central vision. In this review, we highlight current progress and future perspectives of novel and investigational therapeutic strategies in the drug pipeline, including anti-vascular endothelial growth factor (VEGF) agents, bispecific antibodies, biosimilars, small molecules, gene therapy, and long-acting drug delivery strategies for both dry and wet AMD. We anticipate that biologics with dual functionalities and combined therapies with long-acting capabilities will lead the wet AMD pipeline. Sustained-release platforms also show potential. However, significant breakthroughs are yet to be made for dry AMD. The personalized approach might be well suited in the scenario of diverse genetic variations in both conditions. Teaser: AMD is the leading cause of global blindness in the developed world. This article highlights investigational therapeutics, such as antibodies, Bi-specifics, small molecules, biosimilars, gene therapy and long-acting strategies (Port Delivery System), for this condition.

The Effectiveness of Brolucizumab and Aflibercept in Patients with Neovascular Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a progressive, chronic disease of the central area of the retina, which, if untreated, leads to blindness. This study aimed to compare the effectiveness of therapy using anti-VEGF drugs, namely brolucizumab and aflibercept, in patients with neovascular AMD (nAMD) during a monitoring period lasting around 20 weeks. The analysis consisted of 40 patients diagnosed with neovascular age-related macular degeneration, with 20 patients receiving aflibercept (Eylea, Bayer) at a dose of 2 mg/50 µL into the vitreous chamber at the following intervals—3 doses, 4 weeks apart, followed by a fourth dose after 8 weeks. The remaining 20 patients received brolucizumab (Beovu, Novartis) at a dose of 6 mg/50 µL, administered in the following schedule—3 initial doses, 4 weeks apart, with the administration of a fourth dose decided for each patient individually by the doctor, depending on disease activity, assessed through imaging tests. To evaluate treatment effectiveness, the following measurements were used: ‘read distance and near visual acuity’ for each eye separately using the Snellen chart; and non-invasive retinal imaging techniques—optical coherence tomography (OCT) and OCT angiography (OCTA). In patients treated using brolucizumab, during the observation period, statistically significant differences were found in the following parameters: flow area (p = 0.0277); select area (p = 0.0277); FOVEA (p = 0.0073); visus (p = 0.0064). In brolucizumab-treated patients, changes in OCT and OCTA, indicating an improvement, were already visible after the first injection of the drug, whereas in the aflibercept-treated group, changes were only visible after the fourth injection. We found a higher effectiveness of brolucizumab therapy compared to aflibercept in patients with nAMD during an observations period lasting 20 weeks. Our observations are significant, although they require further research.

Effectiveness of Current Treatments for Wet Age-Related Macular Degeneration in Japan: A Systematic Review and Pooled Data Analysis

Purpose

We conducted a systematic review to investigate the effectiveness of clinical treatments for wet age-related macular degeneration (wAMD) in Japanese patients in the decade since anti-vascular endothelial growth factor (VEGF) therapies were introduced.

Methods

PubMed was searched for articles published in English between 1 January 2008 and 30 September 2018 using a multistring search strategy. Reviews were scanned for additional relevant studies and select gray literature was evaluated. Mean and/or median for the logarithm of the minimum angle of resolution (logMAR) visual acuity (VA), central retinal thickness (CRT), and the number of injections after 12 months of treatment were calculated using extracted data. Data were stratified by disease type and treatment modality.

Results

Of 335 studies identified, 94 were selected for data extraction (147 treatment arms; typical AMD, n = 25; polypoidal choroidal vasculopathy [PCV], n = 85). Mean (median) logMAR VA was 0.44 (0.32) for typical AMD and 0.34 (0.31) for PCV; the respective mean number of anti-VEGF injections was 5.6 and 4.6. The mean CRT was approximately 220 μm for both groups. For typical AMD, anti-VEGF monotherapy resulted in better VA outcomes than photodynamic therapy (PDT) alone. For PCV, anti-VEGF monotherapy or anti-VEGF plus PDT combination therapy resulted in better VA and CRT outcomes than PDT monotherapy. Combination therapy required fewer injections than anti-VEGF monotherapy (PCV, 3.2 versus 5.3).

Conclusion

wAMD treatment has advanced dramatically in the years since anti-VEGF drugs were introduced in Japan. Discrete patient populations may benefit from differing management regimens, including the fewer injections required with combination therapy.

Ocular Therapeutics and Molecular Delivery Strategies for Neovascular Age-Related Macular Degeneration (nAMD)

Age-related macular degeneration (AMD) is the leading cause of vision loss in geriatric population. Intravitreal (IVT) injections are popular clinical option. Biologics and small molecules offer efficacy but relatively shorter half-life after intravitreal injections. To address these challenges, numerous technologies and therapies are under development. Most of these strategies aim to reduce the frequency of injections, thereby increasing patient compliance and reducing patient-associated burden. Unlike IVT frequent injections, molecular therapies such as cell therapy and gene therapy offer restoration ability hence gained a lot of traction. The recent approval of ocular gene therapy for inherited disease offers new hope in this direction. However, until such breakthrough therapies are available to the majority of patients, antibody therapeutics will be on the shelf, continuing to provide therapeutic benefits. The present review aims to highlight the status of pre-clinical and clinical studies of neovascular AMD treatment modalities including Anti-VEGF therapy, upcoming bispecific antibodies, small molecules, port delivery systems, photodynamic therapy, radiation therapy, gene therapy, cell therapy, and combination therapies.

Complement Inhibitors in Age-Related Macular Degeneration: A Potential Therapeutic Option

Age-related macular degeneration (AMD) is a multifactorial disease, which can culminate in irreversible vision loss and blindness in elderly. Nowadays, there is a big gap between dry AMD and wet AMD on treatment. Accounting for nearly 90% of AMD, dry AMD still lacks effective treatment. Numerous genetic and molecular researches have confirmed the significant role of the complement system in the pathogenesis of AMD, leading to a deeper exploration of complement inhibitors in the treatment of AMD. To date, at least 14 different complement inhibitors have been or are being explored in AMD in almost 40 clinical trials. While most complement inhibitors fail to treat AMD successfully, two of them are effective in inhibiting the rate of GA progression in phase II clinical trials, and both of them successfully entered phase III trials. Furthermore, recently emerging complement gene therapy and combination therapy also offer new opportunities to treat AMD in the future. In this review, we aim to introduce genetic and molecular associations between the complement system and AMD, provide the updated progress in complement inhibitors in AMD on clinical trials, and discuss the challenges and prospects of complement therapeutic strategies in AMD.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

Subretinal Saline Protects the Neuroretina From Thermic Damage During Laser Induction of Experimental Choroidal Neovascularization in Pigs

Purpose

The purpose of this study was to develop a porcine model for photocoagulation induced choroidal neovascularization (CNV) with high success rate and minimal thermic damage to the neuroretina.

Methods

Experimental CNV was induced by laser photocoagulation in both eyes of 16 domestic pigs. In the left eyes, photocoagulation was preceded by subretinal injection of saline to protect the neuroretina from thermic damage, whereas the right eyes were treated with photocoagulation only. The development of the CNV after 3, 7, 14, 28, and 42 days was evaluated by optical coherence tomography (OCT) scanning, fluorescein angiography, and OCT angiography, and by histology after enucleation.

Results

From day 7 after the photocoagulation, OCT showed subretinal density in all lesions of 14 alive animals, and either fluorescein or OCT angiography confirmed CNV formation in 11 of 14 of the eyes that had received photocoagulation alone and those in which photocoagulation had been preceded by subretinal injection of saline. In all cases pretreated with subretinal saline, the neuroretina was protected from immediate thermic damage. The formation of CNVs were confirmed by histology. For both groups, the largest lesions were observed within 14 days after photocoagulation.

Conclusions

Injection of subretinal saline can protect the retina from thermic damage induced by retinal photocoagulation without reducing the success rate in producing experimental CNV. The effect of interventional studies aimed at reducing photocoagulation induced experimental CNV in pigs can be evaluated within 2 weeks after photocoagulation.

Translational Relevance

This model provides a fundament to develop and evaluate novel treatment methods for neovascular retinal diseases.

Low-Dose Recombinant Adeno-Associated Virus-Mediated Inhibition of Vascular Endothelial Growth Factor Can Treat Neovascular Pathologies Without Inducing Retinal Vasculitis

The wet form of age-related macular degeneration is characterized by neovascular pathologies that, if untreated, can result in edemas followed by rapid vision loss. Inhibition of vascular endothelial growth factor (VEGF) has been used to successfully treat neovascular pathologies of the eye. Nonetheless, some patients require frequent intravitreal injections of anti-VEGF drugs, increasing the burden and risk of complications from the procedure to affected individuals. Recombinant adeno-associated virus (rAAV)-mediated expression of anti-VEGF proteins is an attractive alternative to reduce risk and burden to patients. However, controversy remains as to the safety of prolonged VEGF inhibition in the eye. Here, we show that two out of four rAAV serotypes tested by intravitreal delivery to express the anti-VEGF drug conbercept lead to a dose-dependent vascular sheathing pathology that is characterized by immune cell infiltrates, reminiscent of vasculitis in humans. We show that this pathology is accompanied by increased expression in vascular cell adhesion molecule 1 (VCAM1) and intercellular adhesion molecule 1 (ICAM1), both of which promote extravasation of immune cells from the vasculature. While formation of the vascular sheathing pathology is prevented in immunodeficient Rag-1 mice that lack B and T cells, increased expression of VACM1 and ICAM1 still occurs, indicating that inhibition of VEGF function leads to expression changes in cell adhesion molecules that promote extravasation of immune cells. Importantly, a 10-fold lower dose of one of the vectors that cause a vascular sheathing pathology is still able to reduce edemas resulting from choroidal neovascularization without causing any vascular sheathing pathology and only a minimal increase in VCAM1 expression. The data suggest that treatments of neovascular eye pathologies with rAAV-mediated expression of anti VEGF drugs can be developed safely. However, viral load needs to be adjusted to the tropisms of the serotype and the expression pattern of the promoter.

Treatments for dry age-related macular degeneration: therapeutic avenues, clinical trials and future directions

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the developed world. The identification of the central role of vascular endothelial growth factor (VEGF) in the pathogenesis of neovascular AMD and the introduction of anti-VEGF agents as gold-standard treatment, have drastically changed its prognosis-something yet to be seen in dry AMD. Several therapeutic avenues with a wide variability of targets are currently being investigated in dry AMD. The approaches being investigated to reduce the rate of disease progression include, (1) drugs with antioxidative properties, (2) inhibitors of the complement cascade, (3) neuroprotective agents, (4) visual cycle inhibitors, (5) gene therapy and (6) cell-based therapies. A number of early phase clinical trials have provided promising results, with many more ongoing and anticipated in the near future. In this review, we aim to provide an update of the interventional trials to date and future prospects for the treatment of dry AMD.

PDGF Receptor Alpha Signaling Is Key for Müller Cell Homeostasis Functions

Müller cells, the major retinal macroglia, are key to maintaining vascular integrity as well as retinal fluid and ion homeostasis. Although platelet derived growth factor (PDGF) receptor expression in Müller glia has been reported earlier, their actual role for Müller cell function and intimate interaction with cells of the retinal neurovascular unit remains unclear. To close this gap of knowledge, Müller cell-specific PDGF receptor alpha (PDGFRα) knockout (KO) mice were generated, characterized, and subjected to a model of choroidal neovascularization (CNV). PDGFRα-deficient Müller cells could not counterbalance hypoosmotic stress as efficiently as their wildtype counterparts. In wildtypes, the PDGFRα ligand PDGF-BB prevented Müller cell swelling induced by the administration of barium ions. This effect could be blocked by the PDGFR family inhibitor AC710. PDGF-BB could not restore the capability of an efficient volume regulation in PDGFRα KO Müller cells. Additionally, PDGFRα KO mice displayed reduced rod and cone-driven light responses. Altogether, these findings suggest that Müller glial PDGFRα is central for retinal functions under physiological conditions. In contrast, Müller cell-specific PDGFRα KO resulted in less vascular leakage and smaller lesion areas in the CNV model. Of note, the effect size was comparable to pharmacological blockade of PDGF signaling alone or in combination with anti-vascular endothelial growth factor (VEGF) therapy—a treatment regimen currently being tested in clinical trials. These data imply that targeting PDGF to treat retinal neovascular diseases may have short-term beneficial effects, but may elicit unwarranted side effects given the putative negative effects on Müller cell homeostatic functions potentially interfering with a long-term positive outcome.

Cellular senescence in the aging retina and developments of senotherapies for age-related macular degeneration

Age-related macular degeneration (AMD), a degenerative disease in the central macula area of the neuroretina and the supporting retinal pigment epithelium, is the most common cause of vision loss in the elderly. Although advances have been made, treatment to prevent the progressive degeneration is lacking. Besides the association of innate immune pathway genes with AMD susceptibility, environmental stress- and cellular senescence-induced alterations in pathways such as metabolic functions and inflammatory responses are also implicated in the pathophysiology of AMD. Cellular senescence is an adaptive cell process in response to noxious stimuli in both mitotic and postmitotic cells, activated by tumor suppressor proteins and prosecuted via an inflammatory secretome. In addition to physiological roles in embryogenesis and tissue regeneration, cellular senescence is augmented with age and contributes to a variety of age-related chronic conditions. Accumulation of senescent cells accompanied by an impairment in the immune-mediated elimination mechanisms results in increased frequency of senescent cells, termed “chronic” senescence. Age-associated senescent cells exhibit abnormal metabolism, increased generation of reactive oxygen species, and a heightened senescence-associated secretory phenotype that nurture a proinflammatory milieu detrimental to neighboring cells. Senescent changes in various retinal and choroidal tissue cells including the retinal pigment epithelium, microglia, neurons, and endothelial cells, contemporaneous with systemic immune aging in both innate and adaptive cells, have emerged as important contributors to the onset and development of AMD. The repertoire of senotherapeutic strategies such as senolytics, senomorphics, cell cycle regulation, and restoring cell homeostasis targeted both at tissue and systemic levels is expanding with the potential to treat a spectrum of age-related diseases, including AMD.

Soluble ligands as drug targets

Historically, the main classes of drug targets have been receptors, enzymes, ion channels and transporters. However, owing largely to the rise of antibody-based therapies in the past two decades, soluble protein ligands such as inflammatory cytokines have become an increasingly important class of drug targets. In this Review, we analyse drugs targeting ligands that have reached clinical development at some point since 1992. We identify 291 drugs that target 99 unique ligands, and we discuss trends in the characteristics of the ligands, drugs and indications for which they have been tested. In the last 5 years, the number of ligand-targeting drugs approved by the FDA has doubled to 34, while the number of clinically validated ligand targets has doubled to 22. Cytokines and growth factors are the predominant types of targeted ligands (70%), and inflammation and autoimmune disorders, cancer and ophthalmological diseases are the top therapeutic areas for both approved agents and agents in clinical studies, reflecting the central role of cytokine and/or growth factor pathways in such diseases.