Abstract: Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. AMD most commonly affects older individuals and is characterized by irreversible degeneration of the retinal pigment epithelium and neurosensory retina. Currently, there are limited treatment options for dry AMD outside of lifestyle modification and nutrient supplementation. Risuteganib [Luminate (ALG-1001), Allegro Ophthalmics, CA, USA] is an intravitreally administered inhibitor of integrin heterodimers αVβ3, αVβ5, α5β1, and αMβ2. It is currently undergoing clinical trials for the treatment of dry AMD and diabetic macular edema (DME). Preclinical studies have shown that risuteganib has an effect on the pathways for angiogenesis, inflammation, and vascular permeability. Ongoing clinical trials have had promising results showing improvements in patient best corrected visual acuity (BCVA) and reduced central macular thickness measured by optical coherence tomography (OCT). There is a pressing need for treatments for dry AMD and while risuteganib appears to have a potential benefit for patients, more data are needed before one can truly evaluate its efficacy. This narrative review provides a concise summary of the most up to date data regarding the proposed mechanism of action of risuteganib in the treatment of nonexudative AMD and DME as well as the results from recent phase 1 and phase 2 clinical trials.
Abstract: Statins are used widely to treat hypercholesterolemia and atherosclerotic cardiovascular disease. They have inflammatory and immunomodulatory effects potentially useful for managing systemic autoimmune diseases such as rheumatoid arthritis, lupus erythematosus and multiple sclerosis. Statins also have anti-oxidative and large-vessel endothelial supportive properties that occur independent of their lipid-lowering effects. Additionally, statins can suppress macrophage and microglial activation responsible for initiating inflammatory cytokine release. More than forty percent of adults aged 65 years or older use statins in the United States and Australia, a prevalence that increases with age. The effects of statin usage on ophthalmic practice are probably underrecognized. Cardiovascular disease and age-related macular degeneration (AMD) share common risk factors, consistent with the “vascular model” of AMD pathogenesis that implicates impaired choroidal circulation in Bruch’s membrane lipoprotein accumulation. AMD has a complex multifactorial pathogenesis involving oxidative stress, choroidal vascular dysfunction, dysregulated complement-cascade-mediated inflammation and pro-inflammatory and pro-angiogenic growth factors. Many of these components are hypothetically amenable to the primary (cholesterol lowering) and secondary (anti-inflammatory, anti-oxidative, anti-vasculopathy) effects of statin use. Experimental studies have been promising, epidemiological trails have produced conflicting results and three prospective clinical trials have been inconclusive at demonstrating the value of statin therapy for delaying or preventing AMD. Cumulative evidence to date has failed to prove conclusively that statins are beneficial for preventing or treating AMD.
Abstract: In developed countries, age-related macular degeneration (AMD) is the main cause of visual impairment in the elderly. Though the etiology of AMD is still unclear, it has been well understood that vascular endothelial growth factor (VEGF) is involved in the development of aberrant vasculature that represents the neovascular AMD (nAMD). Hence, VEGF inhibition is a more effective way to control nAMD. Pegaptanib, ranibizumab, and aflibercept are three drugs approved by the US Food and Drug Administration (FDA) to treat nAMD. Bevacizumab (an anti-VEGF medication comparable to ranibizumab) is already widely used off label. Existing anti-VEGF medicines are made up of antibodies or pieces of antibodies. Synthetic designed ankyrin repeat proteins (DARPins) imitate antibodies introduced recently by evolutions in bioengineering technology. These agents are designed to have high specificity and affinity to a specific target, smaller molecular size, and better tissue penetration, making them more stable and longer-acting at less concentration. Abicipar pegol (Allergan, Dublin, Ireland) is a DARPin that interlocks all VEGF-A isoforms. It has a greater affinity for VEGF and a longer intraocular half-life than ranibizumab, making it a feasible anti-VEGF agent. This review describes the properties and efficacy of abicipar, the new anti-VEGF agent, in clinical practice, which aims to improve outcomes, safety, and treatment burden of nAMD.
Abstract: The purpose of this article is to review current literature and data regarding treatment options for age-related macular degeneration (AMD) related to mitochondrial therapy. This article considers the presence of flavoprotein fluorescence as a potential biomarker to test the effectiveness of the treatments. We focus primarily on two major mitochondrial targets, nuclear factor erythroid 2-related factor (NFE2L2) and PGC-1α, that function in controlling the production and effects of reactive oxidative species (ROS) directly in the mitochondria. PU-91 is an FDA approved drug that directly targets and upregulates PGC-1α in AMD cybrid cell lines. Although neither NFE2L2 nor PGC1-α have yet been tested in clinical trials, their effects have been studied in rodent models and offer promising results. MTP-131, or elamipretide?, and metformin are two drugs in phase II clinical trials that focus on the treatment of advanced, non-exudative AMD. MTP-131 functions by associating with cardiolipin (CL) whereas metformin targets adenosine-monophosphate protein kinase (AMPK) in the mitochondria. The current results of their clinical trials are elucidated in this article. The molecular targets and drugs reviewed in this article show promising results in the treatment of AMD. These targets can be further pursued to improve and refine treatment practices of this diagnosis.
Abstract: Dramatic advances in retinal imaging technology over the last two decades have significantly improved our understanding of the natural history and pathophysiology of non-neovascular age-related macular degeneration (AMD). Currently, aside from micronutrient supplements, there are no proven treatments for non-neovascular or dry AMD. Recently, a number of pharmacological agents have been evaluated or are under evaluation for treatment of patients with end-stage dry AMD manifesting as geographic atrophy (GA). It may preferable, however, to intervene earlier in the disease before the development of irreversible loss of visual function. Earlier intervention would require a more precise understanding of biomarkers which may increase the risk of progression from early and intermediate stages to the late stage of the disease. The development of optical coherence tomography angiography (OCTA) has allowed the layers of the retinal microcirculation and choriocapillaris (CC) to be visualized and quantified. Flow deficits in the CC have been observed to increase with age, particularly centrally, and these flow deficits appear to worsen with development and progression of AMD. As such, OCTA-based CC assessment appears to be a valuable new biomarker in our assessment and risk-stratification of AMD. Alterations in the CC may also provide new insights into the pathophysiology of the disease. Enhancement of choriocapillaris function may also prove to be a target of future therapeutic strategies or as a biomarker to monitor the effectiveness of therapy. As such, CC imaging may be anticipated to be an integral tool in the management of dry AMD.
Background: Soft drusen and basal linear deposit (BLinD) are two forms of the same extracellular lipid rich material that together make up an Oil Spill on Bruch’s membrane (BrM). Drusen are focal and can be recognized clinically. In contrast BLinD is thin and diffusely distributed, and invisible clinically, even on highest resolution OCT, but has been detected on en face hyperspectral autofluorescence (AF) imaging ex vivo. We sought to optimize histologic hyperspectral AF imaging and image analysis for recognition of drusen and sub-RPE deposits (including BLinD and basal laminar deposit), for potential clinical application.
Methods: Twenty locations specifically with drusen and 12 additional locations specifically from fovea, perifovea and mid-periphery from RPE/BrM flatmounts from 4 AMD donors underwent hyperspectral AF imaging with 4 excitation wavelengths (λex 436, 450, 480 and 505 nm), and the resulting image cubes were simultaneously decomposed with our published non-negative matrix factorization (NMF). Rank 4 recovery of 4 emission spectra was chosen for each excitation wavelength.
Results: A composite emission spectrum, sensitive and specific for drusen and presumed sub-RPE deposits (the SDr spectrum) was recovered with peak at 510–520 nm in all tissues with drusen, with greatest amplitudes at excitations λex 436, 450 and 480 nm. The RPE spectra of combined sources Lipofuscin (LF)/Melanolipofuscin (MLF) were of comparable amplitude and consistently recapitulated the spectra S1, S2 and S3 previously reported from all tissues: tissues with drusen, foveal and extra-foveal locations.
Conclusions: A clinical hyperspectral AF camera, with properly chosen excitation wavelengths in the blue range and a hyperspectral AF detector, should be capable of detecting and quantifying drusen and sub-RPE deposits, the earliest known lesions of AMD, before any other currently available imaging modality.
Background: Cells of the retinal pigment epithelium (RPE) accumulate different kinds of granules (lipofuscin, melanolipofuscin, melanosomes) within their cell bodies, with lipofuscin and melanolipofuscin being autofluorescent after blue light excitation. High amounts of lipofuscin granules within the RPE have been associated with the development of RPE cell death and age-related macular degeneration (AMD); however, this has not been confirmed in histology so far. Here, based on our previous dataset of RPE granule characteristics, we report the characteristics of RPE cells from human donor eyes that show either high or low numbers of intracellular granules or high or low autofluorescence (AF) intensities.
Methods: RPE flatmounts of fifteen human donors were examined using high-resolution structured illumination microscopy (HR-SIM) and laser scanning microscopy (LSM). Autofluorescent granules were analyzed regarding AF phenotype and absolute number of granules. In addition, total AF intensity per cell and granule density (number of granules per cell area) were determined. For the final analysis, RPE cells with total granule number below 5th or above the 95th percentile, or a total AF intensity ± 1.5 standard deviations above or below the mean were included, and compared to the average RPE cell at the same location. Data are presented as mean ± standard deviation.
Results: Within 420 RPE cells examined, 42 cells were further analyzed due to extremes regarding total granule numbers. In addition, 20 RPE cells had AF 1.5 standard deviations below, 28 RPE cells above the mean local AF intensity. Melanolipofuscin granules predominate in RPE cells with low granule content and low AF intensity. RPE cells with high granule content have nearly twice (1.8 times) as many granules as an average RPE cell.
Conclusions: In normal eyes, outliers regarding autofluorescent granule load and AF intensity signals are rare among RPE cells, suggesting that granule deposition and subsequent AF follows intrinsic control mechanisms at a cellular level. The AF of a cell is related to the composition of intracellular granule types. Ongoing studies using AMD donor eyes will examine possible disease related changes in granule distribution and further put lipofuscin′s role in aging and AMD further into perspective.
