Using a Novel, Subconjunctival, Sustained-Release Mitomycin C Formulation in a Rabbit Model of Filtration Surgery with Gel Stent Implantation

Purpose: To investigate gel stent implantation with and without intraoperative sustained-release mitomycin C (MMC SR) in a rabbit model for gel stent implantation, and to examine aqueous humor outflow (AHO) postimplantation. Methods: Four groups of rabbits were included. Group 1 was untreated (control). Groups 2, 3, and 4 received the gel stent without MMC, with MMC solution (subconjunctival injection), and with MMC SR (subconjunctival injection), respectively. Intraocular pressure (IOP) and AHO were assessed via tonometry and indocyanine green-based angiography, respectively. The main efficacy measure was change in IOP from baseline. Results: Following gel stent implantation, Groups 2, 3, and 4 maintained ≥20% IOP reduction (response) for a median duration of 1 week, 6.5 weeks, and 30 weeks, respectively. Angiography showed normal aqueous humor drainage (Group 1) beginning at the perilimbal trabecular plexus and continuing posteriorly to episcleral outflow vessels. Following implantation, drainage occurred preferentially and directly into the subconjunctival bleb. Conclusions: Gel stent implantation with MMC SR was most effective in achieving sustained, long-term IOP reduction in the rabbit model, compared with implantation with or without MMC solution. Bleb presence and the postimplantation aqueous angiography results indicated redirection of the AHO to the subconjunctival vasculature and presumed lymphatics, suggesting efficient glaucoma filtration to lower IOP in this model. This rabbit model and aqueous angiography may help refine understanding of the mechanism of action of minimally invasive glaucoma surgeries and ultimately translate to improved surgical devices and procedures for patients with glaucoma.

Drug Approval for the Treatment of Geographic Atrophy: How We Got Here and Where We Need to Go

PURPOSE

To discuss the clinical trial results leading to the US Food and Drug Administration (FDA) approval of anti-complement therapies for geographic atrophy (GA), perspectives on functional data from the GA clinical trials, and how lessons from the FDA approval may guide future directions for basic and clinical research in AMD.

DESIGN

Selected literature review with analysis and perspective METHODS: We performed a targeted review of publicly available data from the clinical trials of pegcetacoplan and avacincaptad for the treatment of GA, as well as scientific literature on the natural history of GA and the genetics and basic science of complement in AMD.

RESULTS

The approval of pegcetacoplan and avacincaptad was based on an anatomic endpoint of a reduction in the rate of GA expansion over time. However, functional data from 2 phase 3 clinical trials for each drug demonstrated no visual benefit to patients in the treatment groups. Review of the genetics of AMD and the basic science of the role for complement in AMD provides only modest support for targeting complement as treatment for GA expansion, and alternative molecular targets for GA treatment are therefore discussed. Reasons for the disconnect between anatomic and functional outcomes in the clinical trials of anti-complement therapies are discussed, providing insight to guide the configuration of future clinical studies for GA.

CONCLUSION

Although avacincaptad and pegcetacoplan are our first FDA-approved treatments for GA, results from the clinical trials failed to show any functional improvement after 1 and 2 years, respectively, calling into question whether the drugs represent a "clinically relevant outcome." To improve the chances of more impactful therapies in the future, we provide basic-science rationale for pursuing non-complement targets; emphasize the importance of ongoing clinical research that more closely pins anatomic features of GA to functional outcomes; and provide suggestions for clinical endpoints for future clinical trials on GA.

Faricimab Treat-and-Extend for Diabetic Macular Edema: Two-Year Results from the Randomized Phase 3 YOSEMITE and RHINE Trials

PURPOSE

To evaluate the 2-year efficacy, durability, and safety of dual angiopoietin-2 and vascular endothelial growth factor (VEGF) A pathway inhibition with intravitreal faricimab according to a personalized treat-and-extend (T&E)-based regimen with up to every-16-week dosing in the YOSEMITE and RHINE (ClinicalTrials.gov identifiers, NCT03622580 and NCT03622593, respectively) phase 3 trials of diabetic macular edema (DME).

DESIGN

Randomized, double-masked, noninferiority phase 3 trials.

PARTICIPANTS

Adults with visual acuity loss (best-corrected visual acuity [BCVA] of 25-73 letters) due to center-involving DME.

METHODS

Patients were randomized 1:1:1 to faricimab 6.0 mg every 8 weeks, faricimab 6.0 mg T&E (previously referred to as personalized treatment interval), or aflibercept 2.0 mg every 8 weeks. The T&E up to every-16-week dosing regimen was based on central subfield thickness (CST) and BCVA change.

MAIN OUTCOME MEASURES

Included changes from baseline in BCVA and CST, number of injections, durability, absence of fluid, and safety through week 100.

RESULTS

In YOSEMITE and RHINE (n = 940 and 951, respectively), noninferior year 1 visual acuity gains were maintained through year 2; mean BCVA change from baseline at 2 years (weeks 92, 96, and 100 average) with faricimab every 8 weeks (YOSEMITE and RHINE, +10.7 letters and +10.9 letters, respectively) or T&E (+10.7 letters and +10.1 letters, respectively) were comparable with aflibercept every 8 weeks (+11.4 letters and +9.4 letters, respectively). The median number of study drug injections was lower with faricimab T&E (YOSEMITE and RHINE, 10 and 11 injections, respectively) versus faricimab every 8 weeks (15 injections) and aflibercept every 8 weeks (14 injections) across both trials during the entire study. In the faricimab T&E arms, durability was improved further during year 2, with > 60% of patients receiving every-16-week dosing and approximately 80% receiving every-12-week or longer dosing at week 96. Almost 80% of patients who achieved every-16-week dosing at week 52 maintained every-16-week dosing without an interval reduction through week 96. Mean CST reductions were greater (YOSEMITE/RHINE weeks 92/96/100 average: faricimab every 8 weeks -216.0/-202.6 µm, faricimab T&E -204.5/-197.1 µm, aflibercept every 8 weeks -196.3/-185.6 µm), and more patients achieved absence of DME (CST < 325 μm; YOSEMITE/RHINE weeks 92-100: faricimab every 8 weeks 87%-92%/88%-93%, faricimab T&E 78%-86%/85%-88%, aflibercept every 8 weeks 77%-81%/80%-84%) and absence of intraretinal fluid (YOSEMITE/RHINE weeks 92-100: faricimab every 8 weeks 59%-63%/56%-62%, faricimab T&E 43%-48%/45%-52%, aflibercept every 8 weeks 33%-38%/39%-45%) with faricimab every 8 weeks or T&E versus aflibercept every 8 weeks through year 2. Overall, faricimab was well tolerated, with a safety profile comparable with that of aflibercept.

CONCLUSIONS

Clinically meaningful visual acuity gains from baseline, anatomic improvements, and extended durability with intravitreal faricimab up to every 16 weeks were maintained through year 2. Faricimab given as a personalized T&E-based dosing regimen supports the role of dual angiopoietin-2 and VEGF-A inhibition to promote vascular stability and to provide durable efficacy for patients with DME.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Investigating the effects of 7-ketocholesterol on retinal pigment epithelium bioenergetics

Age-related macular degeneration (AMD) is associated with formation of drusen, clusters of lipids, and oxidized lipid products under the retinal pigment epithelium (RPE). 7-Ketocholesterol (7KC) is a form of oxidized cholesterol present in drusen and is hypothesized to play a role in AMD pathogenesis. The association of 7KC with cellular toxicity and inflammation, key elements of AMD pathology, has been demonstrated. However, the effects of 7KC on altering RPE bioenergetics, a potentially important pathologic process in AMD, are unclear. Herein, we describe the effects of non-lethal doses of 7KC on the bioenergetics and phenotype of RPE cells in culture. Metabolic analysis demonstrated a significant dose-dependent increase in total ATP production rates that was driven primarily by an increase in glycolysis. The increase in glycolysis was accompanied by an increase in glucose uptake and increased expression of hexokinase 1. Increased levels of Translocase of Outer Mitochondrial Membrane 20 and NADH:Ubiquinone Oxidoreductase Core Subunit S1, Succinate dehydrogenase, Ubiquinol-Cytochrome C Reductase Core Protein 2, Cytochrome C Oxidase II, and ATP synthase subunit beta, proteins involved in oxidative phosphorylation (OXPHOS), were also seen. However, specific electron transport chain activity remained unchanged. 7KC-treated cells also demonstrated a change in cellular morphology with decreased expression of epithelial markers. In summary, 7KC has significant effects on the bioenergetics and morphology of RPE cells reflective of findings seen in clinical AMD.

Correlation between hyperreflective foci and visual function testing in eyes with intermediate age-related macular degeneration

BACKGROUND

To investigate the relationship between intraretinal hyperreflective foci (HRF) and visual function in intermediate age-related macular degeneration (iAMD).

METHODS

Retrospective, cross-sectional study. iAMD patients underwent spectral domain optical coherence tomography (SD-OCT) imaging and vision function testing: normal luminance best corrected visual acuity (VA), low luminance VA (LLVA), quantitative contrast sensitivity function (qCSF), low luminance qCSF (LLqCSF), and mesopic microperimetry. Each OCT volume was graded for the presence and number of HRF. Each HRF was graded for: separation from the retinal pigment epithelium (RPE), above drusen, and shadowing. Central drusen volume was calculated by the built-in functionality of the commercial OCT software after manual segmentation of the RPE and Bruch's membrane.

RESULTS

HRF group: 11 eyes; 9 patients; mean age 75.7 years. No-HRF group: 11 eyes; 10 patients; mean age 74.8 years. In linear mixed effect model adjusting for cube-root transformed drusen volume, HRF group showed statistically significant worse VA, LLVA, LLqCSF, and microperimetry. HRF group showed worse cone function, as measured by our pre-defined multicomponent endpoint, incorporating LLVA, LLqCSF and microperimetry (p = 0.018). For eyes with HRF, # of HRF did not correlate with any functional measures; however, % of HRF separated from RPE and # of HRF that created shadowing were statistically associated with low luminance deficit (LLD).

CONCLUSIONS

The association between the presence of HRF and worse cone visual function supports the hypothesis that eyes with HRF have more advanced disease.

Cross-Sectional Study of Cone Function in Age-Related Macular Degeneration Subjects With Non-foveal Nascent Geographic Atrophy

PURPOSE

To determine photoreceptor function in subjects with drusen only and non-foveal nascent geographic atrophy (nGA) intermediate age-related macular degeneration.

METHODS

In this cross-sectional study, 60 eyes from 33 subjects, 30 with drusen only and 30 with non-foveal nGA determined by spectral domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF) underwent testing for best-corrected visual acuity (BCVA), low-luminance visual acuity (LLVA), and qCSF algorithm (area under log contrast sensitivity function [AULCSF]) under both standard photopic and low-luminance (LL AULCSF) conditions. Areas of nGA-associated hypo-autofluorescence (hypo-AF) were graded.

RESULTS

In the drusen group, visual acuity (VA) = 81 letters ± 3 (mean ± SD), LLVA = 65 letters ± 4, AULCSF = 0.99 ± 0.0.5, and LL AULCSF = 0.38 ± 0.04, whereas in the nGA group, VA = 77 ± 4 letters, LLVA = 61± 4, AULCSF = 0.87 ± 0.09, and LL AULCSF = 0.28 ± 0.06. Multivariate analysis of variance among the LLVA, AULCSF, and LL AULCSF did not demonstrate a statistical difference (P = .167), whereas LL AULCSF analyzed by analysis of variance demonstrated a significant difference between the 2 groups (P = .037). Linear regressions demonstrated significant relationships between BCVA and AULCSF in both the drusen and nGA groups (r = 0.83, P < 10^-9 and r = 0.61, P = .0004) but did not correlate with AULCSF under low-luminance conditions (r = 2.9, P = .13) in the nGA group. The total area of hypo-AF was negatively associated with poorer visual functions.

CONCLUSIONS

The use of LL AULCSF and certain features of FAF should be considered in clinical trials of intermediate age-related macular degeneration. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

ANATOMIC AND FUNCTIONAL IMPROVEMENT OF A DRUSENOID PIGMENT EPITHELIAL DETACHMENT: A CASE REPORT

BACKGROUND/PURPOSE

Age-related macular degeneration is the most prevalent cause of permanent vision loss in the developed world. Drusenoid pigment epithelial detachments are a biomarker of age-related macular degeneration disease progression and typically result in poor visual prognosis. Low luminance visual acuity (LLVA) has been previously been shown to correlate with the severity of age-related macular degeneration. However, the degree of spontaneous improvement of this functional outcome is still under investigation.

METHODS

Observational clinical case report.

RESULTS

A drusenoid pigment epithelial detachment that increased in size with the development of hyperreflective foci spontaneously improved with restoration of normal foveal contour over the span of 41 months without progression to geographic atrophy or choroidal neovascularization. Although best-corrected visual acuity remained stable both before and after the pigment epithelial detachment resolution, low luminance visual acuity decreased from a baseline of 59 (20/63 -1) to 39 (20/160 -1) letters over 17 months. However, over the subsequent 24 months, low luminance visual acuity improved by 35 letters to 74 letters (20/32 -2).

CONCLUSION

Drusenoid pigment epithelial detachments can resolve without treatment. Low luminance visual acuity seems to correlate with the anatomic improvement and can improve spontaneously by more than six lines of vision.

Normal- and Low-Luminance Automated Quantitative Contrast Sensitivity Assessment in Eyes With Age-Related Macular Degeneration

PURPOSE

To assess the effectiveness of an active learning approach to measuring the contrast sensitivity function (CSF) in patients with various degrees of dry age-related macular degeneration (AMD) under multiple luminance conditions.

DESIGN

Cross-sectional study.

METHODS

Patients with AMD (26 intermediate AMD, 19 AMD with subretinal drusenoid deposits [SDD], 20 geographic atrophy [GA]) and 23 age-matched controls were tested with the Manifold Contrast Vision Meter (Adaptive Sensory Technology) and the qCSF algorithm, which applies active learning to estimate a model of the CSF's global shape. Testing was performed under conditions of standard and low luminance. For each AMD severity, the area under log CSF (AULCSF) and contrast sensitivities at individual spatial frequencies were calculated for analysis. Low-luminance deficits (LLDs) for visual acuity (VA) and AULCSF were calculated as the difference between standard and low luminance values.

RESULTS

Progressive decreases in AULCSF were observed as disease severity increased. For standard luminance, pairwise comparisons revealed significant differences between control/intermediate AMD (P < .0005), control/SDD (P < .0005), control/GA (P < .0005), and intermediate AMD/GA (P < .005). Similarly, for low luminance, pairwise comparisons revealed significant differences between the controls and each disease group (all P < .0005), in addition to significant differences between intermediate AMD/SDD (P < .005), and intermediate AMD/GA (P < .005). No correlations were found between LLD VA and LLD AULCSF in any AMD groups.

CONCLUSIONS

Contrast sensitivity measured via qCSF under both standard- and low-luminance conditions correlates with advancing stages of dry AMD. The interaction between luminance and contrast sensitivity appears to reflect a different aspect of visual function than the interaction between luminance and VA.

THE ANGIOPOIETIN/TIE PATHWAY IN RETINAL VASCULAR DISEASES: A Review

PURPOSE

To provide a concise overview for ophthalmologists and practicing retina specialists of available clinical evidence of manipulating the angiopoietin/tyrosine kinase with immunoglobulin-like and endothelial growth factor-like domains (Tie) pathway and its potential as a therapeutic target in retinal vascular diseases.

METHODS

A literature search for articles on the angiopoietin/Tie pathway and molecules targeting this pathway that have reached Phase 2 or 3 trials was undertaken on PubMed, Association for Research in Vision and Ophthalmology meeting abstracts (2014-2019), and ClinicalTrials.gov databases. Additional information on identified pipeline drugs was obtained from publicly available information on company websites.

RESULTS

The PubMed and Association for Research in Vision and Ophthalmology meeting abstract search yielded 462 results, of which 251 publications not relevant to the scope of the review were excluded. Of the 141 trials related to the angiopoietin/Tie pathway on ClinicalTrials.gov, seven trials focusing on diseases covered in this review were selected. Vision/anatomic outcomes from key clinical trials on molecules targeting the angiopoietin/Tie pathway in patients with retinal vascular diseases are discussed.

CONCLUSION

Initial clinical evidence suggests a potential benefit of targeting the angiopoietin/Tie pathway and vascular endothelial growth factor-A over anti-vascular endothelial growth factor-A monotherapy alone, in part due to of the synergistic nature of the pathways.

The Relationship Between Central Drusen Volume and Low-Luminance Deficit in Age-Related Macular Degeneration

Purpose

To determine the relationship between central drusen volume and low-luminance deficit (LLD) in visual acuity (VA) in patients with intermediate age-related macular degeneration (AMD).

Methods

In this cross-sectional study, 42 patients with intermediate AMD underwent testing for VA and low-luminance VA (LLVA), as well as spectral-domain optical coherence tomography. LLD was calculated as the difference between VA and LLVA. Central drusen volume was measured in the central 3 mm of the macula, defined as the volume between the inner border of the retinal pigment epithelium and Bruch's membrane.

Results

Mean ± standard deviation (SD) LLD was 0.32 ± 0.12 logMAR and mean ± SD drusen volume was 0.18 ± 0.09 mm³. No linear relationship was identified between central 3 mm drusen volume and LLD (P = 0.215). R² for the bivariate linear model was 0.038 (95% confidence interval 0-0.222). Limitation of the analysis to drusen volumes measured in the central 1 mm of the macula did not impact results (R² = 0.075), nor did incorporation of lens status into the model (R² = 0.067) or censoring of patients with nonfoveal subretinal drusenoid deposits (R² = 0.071).

Conclusions

The amount of drusen within the central 3 mm of the macula does not appear to be related to LLD in intermediate AMD. These measures may be manifestations of different underlying pathophysiological mechanisms.

Translational Relevance

Understanding relationships between markers for AMD progression may help guide development of improved clinical grading scales for AMD.

Protection of human retinal pigment epithelial cells from oxidative damage using cysteine prodrugs

Age-related macular degeneration (AMD) is one of the major causes of vision loss in the elderly in most developed countries. Among other causes, oxidative stress in the retinal pigment epithelium (RPE) has been hypothesized to be a major driving force of AMD pathology. Oxidative stress could be treated by antioxidant administration into the RPE cells. However, to achieve high in-vivo efficacy of an antioxidant, it is imperative that the agent be able to penetrate the tissues and cells. Evidence suggests that lipophilicity governs cellular penetrance. Out of many antioxidant candidates, N-acetyl-L-cysteine (a prodrug of L-cysteine) (NAC) is a potent antioxidant as the bioavailability of the parent drug, L-cysteine, determines the production of glutathione; the universal antioxidant that regulates ROS. To increase the lipophilicity, four ester derivatives of N-acetylcysteine: N-acetylcysteine methyl ester, N-acetylcysteine ethyl ester, N-acetylcysteine propyl ester, and N-acetylcysteine butyl ester were synthesized. To mimic in vitro AMD conditions, hydroquinone, a component of cigarette smoke, was used as the oxidative insult. Cytosolic and mitochondrial protection against oxidative stress were tested using cytosolic and mitochondrial specific assays. The results provide evidence that these lipophilic cysteine prodrugs provide increased protection against oxidative stress in human RPE cells compared with NAC.

Investigating the Effect of Esterification on Retinal Pigment Epithelial Uptake Using Rhodamine B Derivatives

Purpose

This study investigated the effects of esterification and increased lipophilicity on cellular penetration, accumulation and retention in ARPE-19-nic cells using ester functionalized rhodamine B dyes.

Methods

Rhodamine B was esterified to generate four dyes with increasing lipophilicity. Cellular uptake, retention and mitochondrial localization were investigated in vitro using ARPE-19-nic cells using direct intracellular and extracellular and mitochondrial fluorescence quantitation, confocal and high-resolution live cell imaging and co-localization with Mito-GFP.

Results

Cellular penetrance, mitochondrial accumulation, and retention of the esterified dyes were increased in ARPE-19-nic cells compared with the nonesterified parent dye by direct fluorescence quantitation. Imaging demonstrated intracellular accumulation was confined to mitochondria as confirmed by colocalization with Mito-GFP.

Conclusions

Esterification is an effective way to increase lipophilicity of a dye to improve cellular penetration of chemical entities. These observations may be key to improving retinal drug delivery for retinal pigment epithelium–based diseases.

Translational Relevance

Understanding the intracellular distribution of drugs into retinal pigment epithelium cells is a critical component for identifying potential therapies for retinal pigment epithelium–based diseases.

A profile of circulating vascular progenitor cells in human neovascular age-related macular degeneration

Background/objective

A subset of neovascular age-related macular degeneration (nvAMD) subjects appears to be refractory to the effects of anti-VEGF treatment and require frequent intravitreal injections. The vascular phenotype of the choroidal neovascular (CNV) lesions may contribute to the resistance. Animal studies of CNV lesions have shown that cells originating from bone marrow are capable of forming varying cell types in the lesions. This raised the possibility of a similar cell population in human nvAMD subjects.

Materials and methods

Blood draws were obtained from subjects with active nvAMD while patients were receiving standard of care anti-VEGF injections. Subjects were classified as refractory or non-refractory to anti-VEGF treatment based on previous number of injections in the preceding 12 months. Peripheral blood mononuclear cells (PBMCs) were isolated and CD34-positive cells purified using magnetic bead sorting. The isolated cells were expanded in StemSpan SFEM media to increase cell numbers. After expansion, the cells were split and plated in either endothelial or mesenchymal promoting conditions. Phenotype analysis was performed via qPCR.

Results

There was no significant difference in the number of PBMCs and CD34-positive cells between refractory and non-refractory nvAMD subjects. The growth pattern distribution between endothelial and mesenchymal media conditions were very similar between refractory and non-refractory subjects. qPCR and immunostaining demonstrated positive expression of endothelial markers in endothelial media, and markers such as NG2 and αSMA in mesenchymal media. However, analysis of subsequent samples from AMD subjects demonstrated high variability in both the numbers and differentiation properties of this cell population.

Conclusions

CD34+ cells can be isolated from nvAMD subjects and show both endothelial and pericyte-like characteristics after differentiation in certain media conditions. However, nvAMD subjects show high variability in both numbers of cells and differentiation characteristics in repeat sampling. This variability highlights the importance of taking multiple samples from nvAMD subjects for any clinical trials focused on biomarkers for the disease.

Microperimetry for geographic atrophy secondary to age-related macular degeneration

Geographic atrophy (GA) is a progressive, advanced form of age-related macular degeneration leading to visual function impairment and irreversible vision loss. Standard clinical tests to evaluate visual function in patients with GA provide poor anatomic-functional correlation, whereas fundus imaging does not assess the visual function deficit. Microperimetry is a psychophysical visual function test that spatially maps retinal sensitivity and allows for identification of correlation of anatomic features with visual function. In this review, we present an overview of mesopic microperimetry for GA, including commercially available microperimetry devices, strategies to capture a mesopic microperimetry test, and strategies to assess and interpret microperimetry data in patients with GA. We demonstrate the importance of microperimetry data for assessing GA progression and for evaluating visual function loss through anatomic-functional correlations. Although valuable, current microperimetry tests require an extensive time commitment from the patient and examiner, and the development of faster, more reproducible and accessible methods is important to enable broader use of microperimetry in both clinical and research settings.

Pharmacology of Corticosteroids for Diabetic Macular Edema

Purpose

Corticosteroids remain the mainstay of treatment for inflammatory diseases almost 80 years after their first clinical use. Topical ophthalmic formulations of corticosteroids have been available to treat disease of the anterior segment of the eye, but the approval of corticosteroids to treat vitreoretinal diseases, including vein occlusion, diabetic macular edema, and uveitis, has occurred only recently. Although most diseases respond to corticosteroid therapy, some patients are resistant to this therapy and side effects, including cataract and elevated intraocular pressure, can limit their use. The purpose of this review is to detail the basic science of corticosteroids focusing on differences in potency, drug delivery, pharmacokinetics, and gene activation, and how these differences affect safety and efficacy in the treatment of diabetic macular edema.

Methods

A review was conducted of basic science and pharmacology of the corticosteroids used to treat diabetic macular edema.

Results

Clinically available corticosteroids not only have differing potency and pharmacokinetics, but also activate different genes in different target tissues. These differences are associated with distinct efficacy, pharmacokinetic, and safety profiles. It is important to understand these differences in selecting corticosteroids to treat diabetic macular edema.

Conclusions

Recent advances in our understanding of the basic science of corticosteroids can explain clinical differences in these agents regarding efficacy and safety. Importantly, this understanding should allow the future discovery of additional novel corticosteroids to treat diabetic macular edema.

Emixustat Hydrochloride for Geographic Atrophy Secondary to Age-Related Macular Degeneration: A Randomized Clinical Trial

PURPOSE

To determine whether emixustat hydrochloride (emixustat) reduces the rate of enlargement of geographic atrophy (GA) compared with placebo in subjects with age-related macular degeneration (AMD) and to evaluate the safety and tolerability of emixustat over 24 months of treatment.

DESIGN

Multicenter, randomized, double-masked, placebo-controlled, phase 2b/3 clinical trial.

PARTICIPANTS

Patients with GA secondary to AMD, a visual acuity score of at least 35 letters, and GA with a total area of 1.25 to 18 mm² were enrolled.

METHODS

Subjects were randomized (1:1:1:1) to emixustat 2.5 mg, 5 mg, 10 mg, or placebo, administered orally once daily for 24 months. Visits included screening, baseline, and months 1, 2, 3, 6, 9, 12, 15, 18, 21, 24, and 25.

MAIN OUTCOME MEASURES

The primary efficacy end point was the mean annual growth rate of total GA area in the study eye, as measured by a central reading center using fundus autofluorescence (FAF) images. The change from baseline in normal luminance best-corrected visual acuity (NL-BCVA) was a secondary efficacy end point.

RESULTS

Of 508 randomized subjects, 320 completed the study. Demographics and baseline characteristics were comparable between treatment groups. On average, GA lesions in the study eye grew at a similar rate in each group (emixustat: 1.69 to 1.84 mm²/year; placebo: 1.69 mm²/year; P ≥ 0.81). Changes in NL-BCVA were also comparable between groups. Subjects with a larger low luminance deficit (LLD) at baseline (≥20 letters) demonstrated a more rapid growth of GA over 24 months. No relationship was observed between the risk-allele status of the AMD-associated single-nucleotide polymorphisms tested and the growth rate of GA. The most common adverse events in emixustat-treated subjects were delayed dark adaptation (55%), chromatopsia (18%), visual impairment (15%), and erythropsia (15%).

CONCLUSIONS

Emixustat did not reduce the growth rate of GA in AMD. The most common adverse events were ocular in nature and likely related to the drug's mechanism of action. Data gained from this study over a 2-year period add to the understanding of the natural history of GA and the baseline characteristics affecting the growth rate of GA.

SU5416 induces premature senescence in endothelial progenitor cells from patients with age-related macular degeneration

PURPOSE

We recently demonstrated increased frequency and growth potential of late outgrowth endothelial progenitor cells (OECs) in patients with neovascular age-related macular degeneration (nvAMD). This study investigated the effects of short- and long-term in vitro inhibition of vascular endothelial growth factor (VEGF) Receptor-2 (VEGFR-2) signaling by SU5416 and other inhibitors of the VEGF signaling pathway in OECs.

METHODS

OECs, from the peripheral blood of patients with nvAMD, and human umbilical vein endothelial cells were grown in the presence of SU5416, other VEGFR-2 tyrosine kinase inhibitors (TKIs), and inhibitors of phosphatidylinositol 3'-Kinase (PI3K)/protein kinase B (Akt) and protein kinase C (PKC) in complete angiogenic medium. Apotosis was assessed after 48 h using the fluorescein isothiocyanate Annexin V method. Cell counts were performed for 10 days, and features of senescence were analyzed using senescence-associated β-galactosidase staining, the telomeric repeat amplification protocol for telomerase activity, Southern blot analysis for mean telomere length, flow cytometric analysis for cell-cycle arrest, and western blot for p53 and p21. Control OECs, cells treated for 7 days with inhibitors, as well as naturally senescent OECs were analyzed for expression of different endothelial antigens, including VEGFR-2 and the receptor for stromal cell-derived factor 1, chemokine receptor 4 (CXCR-4). Migration in vitro to VEGF and stromal cell-derived factor 1 of OECs was assessed.

RESULTS

SU5416, other VEGFR-2 TKIs, and inhibitors of PI3K, Akt, and PKC induced apoptosis, inhibited long-term proliferation, reduced telomerase activity, and induced premature senescence and cell-cycle arrest in OECs as well as in human umbilical vein endothelial cells. Naturally senescent cells and cells rendered senescent by VEGFR-2 TKIs had reduced VEGFR-2 and CXCR-4 expression and demonstrated reduced migratory ability to VEGF.

CONCLUSIONS

This study demonstrates apoptosis upon short-term inhibition and inhibition of long-term survival of OECs from patients with nvAMD by SU5416, presumably via PI3K/Akt and/or PKC-mediated reduction in telomerase activity and subsequent induction of premature senescence, which is accompanied by impaired endothelial activity. Therefore, induction of premature senescence in endothelial cells may represent a potential therapeutic target in nvAMD.

Cigarette smoke-related hydroquinone induces filamentous actin reorganization and heat shock protein 27 phosphorylation through p38 and extracellular signal-regulated kinase 1/2 in retinal pigment epithelium: implications for age-related macular degeneration

Retinal pigment epithelium (RPE)-derived membranous debris named blebs, may accumulate and contribute to sub-RPE deposit formation, which is the earliest sign of age-related macular degeneration (AMD). Oxidative injury to the RPE might play a significant role in AMD. However, the underlying mechanisms are unknown. We previously reported that hydroquinone (HQ), a major pro-oxidant in cigarette smoke, foodstuff, and atmospheric pollutants, induces actin rearrangement and membrane blebbing in RPE cells as well as sub-RPE deposits in mice. Here, we show for the first time that phosphorylated Heat shock protein 27 (Hsp27), a key regulator of actin filaments dynamics, is up-regulated in RPE from patients with AMD. Also, HQ-induced nonlethal oxidative injury led to Hsp27mRNA up-regulation, dimer formation, and Hsp27 phosphorylation in ARPE-19 cells. Furthermore, we found that a cross talk between p38 and extracellular signal-regulated kinase (ERK) mediates HQ-induced Hsp27 phosphorylation and actin aggregate formation, revealing ERK as a novel upstream mediator of Hsp27 phosphorylation. Finally, we demonstrated that Hsp25, p38, and ERK phosphorylation are increased in aging C57BL/6 mice chronically exposed to HQ, whereas Hsp25 expression is decreased. Our data suggest that phosphorylated Hsp27 might be a key mediator in AMD and HQ-induced oxidative injury to the RPE, which may provide helpful insights into the early cellular events associated with actin reorganization and bleb formation involved in sub-RPE deposits formation relevant to the pathogenesis of AMD.

Evaluation of clearance mechanisms with transscleral drug delivery

PURPOSE

The goal of this study was to examine elimination pathways when delivering subconjunctivally administered hydrophilic agents to the retinas of rat eyes.

METHODS

The distribution of sodium fluorescein released from an episcleral implant was compared in live and postmortem eyes. Elimination of the subconjunctivally administered hydrophilic agent IgG through blood and lymphatic vessels was investigated by immunohistochemistry. Additionally, lymphatic elimination of subconjunctivally injected sodium fluorescein was quantitatively evaluated.

RESULTS

NaFl released from an episcleral implant was successfully delivered to the subretinal space in the postmortem eye but failed to do so in the live eye. Immunohistochemical visualization of the conjunctival tissue demonstrated dense distribution of blood and lymphatic vessels while also confirming the elimination of subconjunctivally administered IgG through these same vessels. The lymphatic elimination rate after injection of 75.6 μg of a hydrophilic agent, sodium fluorescein, into the subconjunctival space was determined to be 105 ng/min between 30 and 60 minutes.

CONCLUSIONS

Conjunctival blood and lymphatic vessel elimination considerably limit transscleral hydrophilic drug delivery to the retina.

Episcleral clearance of sodium fluorescein from a bioerodible sub-tenon's implant in the rat

We quantified episcleral drug clearance of sodium fluorescein (NaFl) in rats to examine the hypothesis that there is rapid clearance of episcleral water soluble drugs, and that this rapid clearance may limit the amount of drug that is able to reach the posterior segment from an episcleral location. 2 mm implants containing either 12 or 22 microg of NaFl were manufactured and in vitro release rates were determined. Implants were placed in the sub-Tenon's space and the amount of drug remaining in the conjunctiva/sclera/choroid complex (CSCC) at various time points was quantified following tissue solubilization and fluorescence quantification using a spectrofluorometer. Kinetics of NaFl clearance was determined in live animals, following euthanasia and in animals in which choroidal non-perfusion had been achieved with indocyanine green-enhanced 810 nm diode laser thrombosis of the choroidal vasculature. Choroidal non-perfusion in these laser-treated rats was verified with Concavalin-A staining of choroidal flatmounts. In vitro, >99% of drug was released by 25 min for the low dose implants, and by 60 min for the high dose implants. In vivo, both implant doses were >99% cleared from the episcleral tissue by 3 h. By 7 h, an average of only 0.14 +/- 0.131 ng of NaFl per mg of wet tissue weight (mean +/- SD) remained in the CSCC with the low dose implant, and 0.29 +/- 0.428 ng of NaFl per mg of wet tissue weight remained in animals with the high dose implant. By comparison, in euthanized animals at 7 h following sub-Tenon's implantation, 432.0 +/- 181.40 ng of NaFl per mg of wet tissue weight was in the episcleral tissue of animals with the low dose implant, and of 787.8 +/- 409.89 ng of NaFl per mg of wet tissue weight remained in the animals with the high dose implant. In live animals with selective thrombosis of the choroidal vasculature, the difference in the amount of drug remaining in the episcleral tissue as compared to control live animals was not significant at all time points for both implant doses. In conclusion, there is rapid clearance of episcleral NaFl delivered from a bioerodible sub-tenon's implant. The clearance mechanisms are dramatically reduced following euthanasia, suggesting that elimination is occurring via active physiologic mechanisms, rather than by passive diffusion clearance (CL(diff)) (Pfister et al., 2003). Interestingly, the choroid does not appear to play a prominent role as clearance of episcleral NaFl was not affected by elimination of choroidal blood flow. Further work is needed to delineate the pathways of episcleral drug clearance.

FcRn receptor-mediated pharmacokinetics of therapeutic IgG in the eye

PURPOSE

The goal of this study was to determine the role of the neonatal Fc (FcRn) receptor in eliminating intravitreally administered full-length immunoglobulin G (IgG) across the blood-retinal barrier.

METHODS

FcRn receptor expression in normal and laser photocoagulated retinas was compared quantitatively by real-time RT-PCR. The distribution of intravitreally administered full-length IgG was investigated and compared in wild-type and FcRn knockout mouse eyes as well as normal and laser-photocoagulated rat eyes at several time points. Additionally, the pharmacokinetics of intravitreally injected full-length IgG and chicken immunoglobulin Y (IgY) was compared in the normal rat retina.

RESULTS

Intravitreally administered full-length IgG overcame the inner limiting membrane and diffused into the deeper retinal structures in both normal and laser-photocoagulated retinas. Interestingly, IgG was eliminated across the blood-retinal barrier into the blood system in the normal retina, whereas IgY was not. In addition, full-length IgGs did not penetrate across the blood-retinal barrier in the FcRn knockout mouse. Intravitreally injected IgGs were eliminated into the blood system more rapidly in laser-photocoagulated eyes when compared to normal control eyes because of FcRn receptor upregulation in the laser-photocoagulated retina.

CONCLUSIONS

FcRn plays an important role in eliminating intravitreally administered full-length IgGs across the blood-retina barrier into the systemic blood system.

Nanoparticle-integrin antagonist C16Y peptide treatment of choroidal neovascularization in rats

Choroidal neovascularization (CNV) is the major cause of severe vision loss in patients with age-related macular degeneration (AMD). Present drug delivery may be limited by poor delivery to the choroid where CNV originates. The goal of this study was to develop a drug delivery system to deliver an integrin-antagonist peptide to the sub-retinal space. We developed polylactic acid/polylactic acid-polyethylene oxide nanoparticles (PLA/PLA-PEO) encapsulating the water-soluble integrin-antagonist peptide, C16Y (C16Y-NP). The PLA/PLA-PEO nanoparticles were 302+/-85.1 nm in size and demonstrated a two-week sustained release, in vitro, of encapsulated C16Y. Injected nanoparticles did not demonstrate retinal toxicity as determined by histopathology. C16Y peptide solution or C16Y-NP was injected 5 or 9 days post laser photocoagulation. A single intravitreal injection of C16Y peptide and C16Y-NP solution at both 5 days and 9 days post laser photocoagulation statistically inhibited CNV (p<0.05). However, for the day 5 injections the area of choroidal neovascularization on day 12 was smaller for C16Y-NP than for C16Y peptide solution (p<0.05) because of the short vitreous half-life of C16Y peptide solution. These results demonstrate the importance of sustained release delivery for the treatment of choroidal neovascularization associated with age-related macular degeneration. The intravitreally administered PLA/PLA-PEO containing coumarin was found to penetrate the retina and localize to the RPE. These results suggest that nanoparticles of biodegradable polymers may be a potential useful delivery system for intravitreal injection of drugs in the treatment of AMD.

Investigating the movement of intravitreal human serum albumin nanoparticles in the vitreous and retina

PURPOSE

To investigate the movement of intravitreally injected human serum albumin nanoparticles (HSA-NP) with respect to nanoparticle surface charge and retinal injury.

METHODS

HSA-NPs were developed by a desolvation technique. HSA-NPs were cationized by covalent coupling of hexamethylenediamine on the particle surface. Either anionic or cationic HSA-NPs were injected to determine the effect of surface charge on intravitreal nanoparticle movement. HSA-NPs were injected intravitreally into both normal and laser photocoagulated eyes to examine the effect of the integrity of retinal tissue on the retinal penetration. The retinal penetration of fluorescence labeled anionic HSA-NPs was investigated by confocal microscopy.

RESULTS

Anionic particles (-33.3+/-6.1 mV) more easily diffused through the 3-dimensional vitreal network of collagen fibrils than did their cationic counterparts (11.7+/-7.2 mV). In the laser photocoagulated retina, more HSA-NPs were detected in the choroidal space, compared to the normal retina. The immunohistochemical studies indicated that HSA-NPs were taken up into Müller cells.

CONCLUSIONS

The movement of intravitreal nanoparticles depended on both nanoparticles surface charge and retinal injury. The Müller cells might play an important role in the retinal penetration of nanoparticles. The anionic HSA-NP is a promising drug or gene delivery carrier to the sub-retinal space and RPE.

Late outgrowth endothelial progenitor cells in patients with age-related macular degeneration

PURPOSE

To evaluate the feasibility of isolating and expanding endothelial progenitor cells (EPCs), in the form of late outgrowth endothelial progenitor cells (OECs), from the peripheral blood of an aged population, particularly patients affected by different forms of AMD.

METHODS

Peripheral blood mononuclear cells were collected from young control subjects (n = 18) and from elderly subjects with non-AMD/low-risk dry AMD (n = 15), high-risk dry AMD (n = 6), or neovascular AMD (nvAMD; n = 32); cultured in established conditions; and observed for appearance of OEC clusters and growth characteristics on expansion. Expression of VEGF receptor-2 (KDR) in OECs after expansion was determined by Western blot. Plasma samples of study subjects were analyzed for CRP and VEGF levels.

RESULTS

OEC cultures were successfully generated from a similar number of subjects in each group. After adjustment for all other variables, subjects with high-risk dry AMD had a 5.6-fold higher number of OEC clusters per 20 mL blood, and subjects with nvAMD had a 5.1-fold high number than did subjects with non-AMD/low-risk dry AMD (P < 0.05). High-risk dry AMD generated 63 times more (NS) and nvAMD 32-times more (P < 0.05) OECs on expansion of clusters than did non-AMD/low-risk dry AMD. Population doubling occurred significantly faster in cultures from nvAMD eyes compared to non-AMD/low-risk dry AMD eyes. In addition, a significant correlation between the number of OEC clusters, expanded OECs and levels of KDR was demonstrated.

CONCLUSIONS

An OEC population was isolated and expanded from the blood of elderly control and AMD-affected patients and demonstrated significantly higher number of initial OEC clusters and expansion potential of OECs in patients at risk for or already affected by nvAMD. OECs may be used for further phenotypic, genetic, and functional analyses in patients with nvAMD.

Mapping of the neonatal Fc receptor in the rodent eye

PURPOSE

The neonatal Fc receptor (FcRn) has been known to modulate IgG transport and protect against IgG catabolism, resulting in extension of the serum half-life of IgG. The goal of this study was to localize FcRn receptor expression in the rat's eye.

METHODS

The cornea, retina, conjunctiva, ciliary body and iris, retinal pigment epithelium and choroid, and lens were dissected from each rat's eye, and total RNA was purified. The first-strand cDNAs were synthesized and subjected to PCR reaction. For control samples, reverse transcriptase was omitted. A monoclonal antibody against the FcRn heavy chain was used to localize the distribution of the FcRn receptor in ocular tissues. Lymphatic vessels and blood vessels were stained with a rabbit anti-mouse lymphatic vessel endothelial receptor-1 polyclonal antibody and a rabbit anti-human von Willebrand factor polyclonal antibody, respectively.

RESULTS

RT-PCR demonstrated expression of FcRn RNA in cornea, retina, conjunctiva, ciliary body and iris, and lens but absence of expression in the retinal pigment epithelium and choroid. Immunohistochemistry and double staining confirmed the expression of FcRn receptor to the conjunctival lymphatic vessels but not in the conjunctival blood vessels. In the ciliary body, the FcRn receptor was found to be expressed in both the nonpigmented ciliary epithelium and the ciliary blood vessels. The expression of FcRn receptor was confirmed in the retinal blood vessels, iris blood vessels, optic nerve vascular structures, corneal epithelium and endothelium, and lens epithelium.

CONCLUSIONS

The FcRn receptor is expressed in multiple ocular tissues. The blood-ocular barrier showed FcRn receptor expression, indicating that IgG transport from ocular tissues to the blood system may use this receptor. The role of the FcRn receptor in the anterior segment and the conjunctiva remains unclear.

Angiogenesis inhibition and choroidal neovascularization suppression by sustained delivery of an integrin antagonist, EMD478761

PURPOSE

To evaluate the angiogenic inhibitory effects of an alpha(v)beta(3)/alpha(v)beta(5) integrin antagonist, EMD478761, released from a polymeric implant in a chick chorioallantoic membrane (CAM) assay and laser-induced experimental choroidal neovascularization (CNV) in rats.

METHODS

Polyvinyl alcohol-based reservoir implants releasing EMD478761 were designed for placement onto a CAM or intravitreally in rats. In vitro release rates of the implants were measured using HPLC. Angiogenesis was induced on 10-day-old chick embryos by basic fibroblast growth factor (bFGF), and areas of neovascularization were measured. Experimental CNV was induced in the Brown-Norway rat with a diode laser. EMD478761 or sham microimplants were placed within the vitreous chamber of Brown-Norway rats. Two weeks later, areas of CNV were determined by FITC-dextran staining of choroidal flatmounts.

RESULTS

Sustained delivery of EMD478761 significantly inhibited bFGF-induced angiogenesis in CAM, as determined by a reduction in angiogenesis areas, without drug toxicity to the normal CAM vasculature. In an experimental rat model, intravitreal EMD478761 implants significantly suppressed laser-induced CNV compared with intravitreal sham implants, with the mean area reduced by 63% (P < 0.05).

CONCLUSIONS

Sustained delivery of EMD478761demonstrates potent antiangiogenic properties in vivo. These results suggest that an EMD478761 implant may be beneficial in the treatment of neovascular ocular diseases.

Drug elimination kinetics following subconjunctival injection using dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

To determine the elimination rates of subconjunctivally injected model drugs using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

METHODS

Gadolinium-diethylenetriaminopentaacetic acid (Gd-DTPA) and gadolinium-albumin (Gd-albumin) were injected in rabbits. Experiments were performed in vivo and post mortem and injection volumes of 200 and 600 microl were administered. Signal intensity values from MR images were converted to concentration of contrast agent to determine the mass clearance rates from subconjunctival space.

RESULTS

Injection volume did not have a significant effect on clearance rate for both Gd-DTPA and Gd-albumin. The clearance rate of Gd-DTPA in vivo was about nine times faster than that post mortem. The in vivo and post mortem clearance rates of Gd-albumin were not significantly different. The in vivo half-life of Gd-DTPA was about 22 min while that of Gd-albumin was about 5.3 h.

CONCLUSIONS

DCE-MRI was used to quantitatively compare the subconjunctival clearance rates of Gd-DTPA and Gd-albumin. Dynamic clearance mechanisms present in vivo significantly reduced the subconjunctival concentration of Gd-DTPA but not Gd-albumin. Lymphatic clearance does not seem to be as significant as clearance by blood, as evidenced by data from Gd-albumin injections. Larger injection volumes may allow for longer retention times and prolonged release of drug.

A Pharmacokinetic and Safety Evaluation of an Episcleral Cyclosporine Implant for Potential Use in High-Risk Keratoplasty Rejection

PURPOSE

To determine the short and long-term pharmacokinetics and assess the toxicity of a cyclosporine (CsA) episcleral implant for the prevention of high-risk keratoplasty rejection.

METHODS

CsA episcleral implants were made with a high (implant A) or low (implant B) release rate, and in vitro release rates were performed. Short-term pharmacokinetics were performed in rabbits using implant B, and the spatial and temporal spread of drug was observed by sampling from multiple corneal and conjunctival sites at 3 and 72 hours. Implant A was used in long-term pharmacokinetic studies in dogs aged more than 1 year. An ocular toxicity study was performed in dogs older than 1 year.

RESULTS

A high release rate was observed with both implants over the initial 5 months followed by a steady state release. The cumulative release over the 400-day assay period from implants A and B was 3.8 +/- 0.3 and 2.3 +/- 0.3 mg, respectively. In the short-term pharmacokinetic studies, the cornea had CsA concentrations of 0.15 +/- 0.06, 0.07 +/- 0.02, and 0.05 +/- 0.02 microg/mg at sites centered 8, 13, and 18 mm away from the implant site, respectively. In the long-term pharmacokinetic studies, corneal CsA levels ranged from 0.18 +/- 0.06 to 0.009 +/- 0.004 microg/mg during the 1-year study. There were no signs of ocular toxicity at 1 year.

CONCLUSIONS

Episcleral implants are safe and effective at delivering therapeutic CsA levels to the cornea to potentially prevent corneal allograft rejection. The implant can be surgically inserted at the time of penetrating keratoplasties, since the implant achieves therapeutic levels as early as 3 hours.

Assessment of subconjunctival and intrascleral drug delivery to the posterior segment using dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

Sustained-release intravitreal drug implants for posterior segment diseases are associated with significant complications. As an alternative, subconjunctival infusions of drug to the episclera of the back of the eye have been performed, but results in clinical trials for macular diseases showed mixed

RESULTS

To improve understanding of transscleral drug delivery to the posterior segment, the distribution and clearance of gadolinium-diethylene-triamino-penta-acetic acid (Gd-DTPA) infused in the subconjunctival or intrascleral space was investigated by means of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

METHODS

In anesthetized rabbits, catheters were placed anteriorly in the subconjunctival or intrascleral space and infused with Gd-DTPA at 1 and 10 muL/min. Distribution and clearance of Gd-DTPA were measured using DCE-MRI. Histologic examination was performed to assess ocular toxicity of the delivery system. results. Subconjunctival infusions failed to produce detectable levels of Gd-DTPA in the back of the eye. In contrast, intrascleral infusions expanded the suprachoroidal layer and delivered Gd-DTPA to the posterior segment. Suprachoroidal clearance of Gd-DTPA followed first-order kinetics with an average half-life of 5.4 and 11.8 minutes after intrascleral infusions at 1 and 10 muL/min, respectively. Histologic examination demonstrated expansion of the tissues in the suprachoroidal space that normalized after infusion termination.

CONCLUSIONS

An intrascleral infusion was successful in transporting Gd-DTPA to the posterior segment from an anterior infusion site with limited anterior segment exposure. The suprachoroidal space appears to be an expandible conduit for drug transport to the posterior segment. Further studies are indicated to explore the feasibility of clinical applications.

An apolipoprotein E variant may protect against age-related macular degeneration through cytokine regulation

Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness among the elderly in Western countries. Genetic factors, age, cigarette smoking, nutrition, and exposure to light have been identified as AMD risk factors. In this study, we investigated the association between ApoE C112R/R158C single nucleotide polymorphisms (which determine the E2, E3, and E4 isoforms) and age-related macular degeneration (AMD), and the mechanism underlying the association. Genomic DNA was extracted from 133 clinically screened controls, 94 volunteers with a younger mean age, 120 patients with advanced AMD, and 40 archived ocular AMD slides for single nucleotide polymorphism typing. The effects of recombinant ApoE isoforms on CCL2 (a chemokine), CX3CR1 (a chemokine receptor), and VEGF (a cytokine) expression in cultured human retinal pigment epithelium (RPE) cells were tested and serum cholesterol profiles of the clinically screened subjects were analyzed. ApoE112R (E4) distribution differed significantly between AMD patients and controls. ApoE112R allele frequency was 10.9% in the AMD group when compared with 16.5% in the younger controls and 18.8% in the clinically screened controls. The pathologically diagnosed archived AMD cases had the lowest allele frequency of 5%. No significant differences in ApoE158C (E2) distribution were observed among the groups. A meta-analysis of 8 cohorts including 4,289 subjects showed a strong association between AMD and 112R, but not 158C. In vitro studies found that recombinant ApoE suppresses CCL2 and VEGF expression in RPE cells. However, the E4 isoform showed more suppression than E3 in both cases. These results further confirm the association between ApoE112R and a decreased risk of AMD development. The underlying mechanisms may involve differential regulation of both CCL2 and VEGF by the ApoE isoforms.

A novel bioerodible deep scleral lamellar cyclosporine implant for uveitis

PURPOSE

To determine the feasibility, safety, and effectiveness of an episcleral or deep scleral lamellar sustained release cyclosporine (CsA) device in a naturally occurring animal model of uveitis.

METHODS

A two-compartment perfusion chamber was used to assess in vitro human and equine scleral permeability of fluorescein, dexamethasone-fluorescein, or CsA. A biodegradable, matrix-reservoir CsA implant was designed, and release rates of CsA were determined in vitro. Tissue CsA levels were measured in eyes with the implant. Horses with equine recurrent uveitis (ERU) received episcleral or deep scleral lamellar CsA implants and were monitored for up to 3 years.

RESULTS

Dexamethasone-fluorescein and CsA penetrated the in vitro equine sclera poorly; however, low but detectable levels of CsA were detected intraocularly in vivo. The implant placed episclerally failed to control inflammatory episodes in ERU. CsA implants placed in the deep sclera adjacent to the suprachoroidal space resulted in high levels of CsA in most ocular tissues. In clinical equine patients with ERU, frequency of uveitic flare-ups was significantly decreased after implantation of a deep scleral lamellar CsA implant.

CONCLUSIONS

Diffusion of CsA across the sclera from the episcleral space was not a feasible method of drug delivery to the equine eye. However, placing a deep scleral lamellar CsA implant adjacent to the suprachoroidal space was effective in achieving therapeutic ocular drug concentrations and controlling uveitis in horses with ERU.

SAFETY AND PHARMACOKINETICS OF A PRESERVATIVE-FREE TRIAMCINOLONE ACETONIDE FORMULATION FOR INTRAVITREAL ADMINISTRATION

PURPOSE

The safety and pharmacokinetics of a triamcinolone acetonide (TA) preservative-free (TA-PF) formulation were investigated after intravitreal administration in rabbits.

METHODS

A TA-PF formulation was prepared as a sterile 40-mg/mL or 160-mg/mL suspension in single-use vials by adding TA powder to 0.5% hydroxypropyl methylcellulose in normal saline. TA-PF (4-mg and 16-mg doses) and Kenalog (Bristol-Myers-Squibb, Princeton, NJ) (4-mg dose) were injected into the vitreous of separate groups of rabbits, and drug levels were measured in the vitreous over time with HPLC. Ocular toxicology (clinical examination, serial electroretinography, and histopathologic analysis) was evaluated in a separate group of animals after intravitreal TA-PF injection.

RESULTS

The half-lives of the injection amount in the vitreous, 4-mg TA-PF, 16-mg TA-PF, and 4-mg Kenalog, were found to be 24 days, 39 days, and 23 days, respectively. There were no signs of toxicities by clinical examination after TA-PF injection. Serial electroretinograms of rabbits receiving either 4-mg or 16-mg intravitreal TA-PF injections remained normal over time. Histopathologic analysis showed normal ocular tissues in animals receiving either 4-mg or 16-mg intravitreal TA-PF injections.

CONCLUSION

The half-life of TA in the vitreous after a 4-mg injection of either TA-PF or Kenalog was comparable. A 16-mg dose of TA-PF produced a long vitreous half-life, and this may be of clinical benefit in patients requiring 6 months of drug exposure in the eye for a chronic disease.

A rabbit model for assessing the ocular barriers to the transscleral delivery of triamcinolone acetonide

Transscleral delivery of triamcinolone acetonide into the vitreous using sub-Tenon's injections may be a safer alternative to reduce the sight-threatening complications of direct intravitreal injections. However, sub-Tenon's injections have demonstrated low and poorly sustained vitreous drug levels in animal studies. To improve our understanding of the clearance mechanisms of corticosteroids, we evaluated vitreous drug levels following sub-Tenon's injection of triamcinolone acetonide in rabbits with selective elimination of conjunctival lymphatic/blood vessels and the choroid. Pigmented rabbits were given a sub-Tenon's injection of a preservative-free triamcinolone acetonide formulation of either a 10- or 20-mg dose in the superotemporal quadrant. The effect eliminating both conjunctival and choroidal clearance was evaluated by injecting the drug, followed by immediate euthanasia, effectively terminating both lymph and blood flow in the conjunctiva and choroid. To inhibit only the clearance from conjunctival lymphatics/blood vessels of a sub-Tenon's injection of triamcinolone acetonide, a group of rabbits had a 'conjunctival window' created by incising an 7 mmx7 mmx7 mm square through the conjunctiva to bare sclera in the superotemporal quadrant. To eliminate only the clearance of drug from the choroidal circulation, cryotherapy was performed in another group of rabbits creating a chorioretinal scar in the superotemporal quadrant. Following the sub-Tenon's drug injection, the eyes were enucleated in all groups after 3 hr and vitreous drug levels were measured with HPLC. In normal animals, a 10-mg sub-Tenon's injection showed no detectable vitreous drug levels; however, a 20-mg injection showed positive vitreous drug levels. This suggested that collectively, the transscleral clearance mechanisms inhibiting delivery into the vitreous may be saturated with a drug depot that has a higher release rate. A 10-mg sub-Tenon's drug depot was able to deliver drug into the vitreous when both the conjunctival and choroidal drug clearance was eliminated by euthanizing the animal immediately following the drug injection. In rabbits that had only a 'conjunctival window', selectively eliminating conjunctival drug clearance, vitreous drug levels were detected. However, in rabbits that had only cryotherapy, selectively eliminating choroidal drug clearance, vitreous drug levels were not detected suggesting that the conjunctival lymphatics/blood vessels may be an important barrier to the transscleral delivery of triamcinolone acetonide. Variability in the vitreous drug levels between rabbits in each group precluded statistical testing. In summary, the rabbit appeared to demonstrate saturable ocular barriers to transscleral delivery of triamcinolone acetonide into the vitreous following a sub-Tenon's injection. The results suggested that the conjunctival lymphatics/blood vessels may be an important barrier to the delivery of triamcinolone acetonide to the vitreous in this rabbit model. The barrier location and clearance abilities of the ocular tissues are important to consider when developing a successful transscleral drug delivery system. Animal models, retaining the dynamics of blood and lymph flow, may improve the basic understanding of the ocular barriers involved with transscleral drug transport and warrants further investigation.

Serum inflammatory markers in diabetic retinopathy

PURPOSE

To evaluate the association of serum factors with the severity of diabetic retinopathy and to assess their presence in retinal tissue obtained at autopsy.

METHODS

The following serum factors of 93 subjects were examined at the National Eye Institute (NEI) clinical center: the chemokines regulated on activation, normal T-cell expressed and presumably secreted (RANTES)/CCL5, epithelial neutrophil activator (ENA)-78/CXCL5, interferon-induced protein (IP)-10/CXCL10, stromal cell-derived factor (SDF)-1alpha/CXCLl2, monocyte chemoattractant protein (MCP)-1/CCL2, macrophage inflammatory protein (MIP)-1alpha/CCL3, interleukin (IL)-8/CXCL8; the cytokine IL-6; the cell adhesion molecules intercellular adhesion molecule (ICAM-1/CD54) and vascular cell adhesion molecule (VCAM/CD106); and the growth factor vascular endothelial growth factor (VEGF). Logistic regression was performed to assess the association of these factors with age, sex, severity of retinopathy, hemoglobin A(1C), total cholesterol, creatinine, duration of diabetes, and presence of macular edema. The outcome assessed was severity of retinopathy. Frozen sections of two donor eyes obtained at autopsy from a donor with documented severe nonproliferative diabetic retinopathy and diabetic macular edema and of a normal nondiabetic eye were processed by immunoperoxidase staining with primary antibodies against RANTES, MCP-1, ICAM-1, and LFA-1alpha/CD11a.

RESULTS

The levels of RANTES and SDF-1alpha were significantly elevated in patients with at least severe nonproliferative diabetic retinopathy compared with those with less severe diabetic retinopathy (P < 0.001 and 0.007, respectively). Positive immunostaining was observed in the inner retina for MCP-1 and RANTES of the patient with diabetes. Staining was strongly positive throughout the diabetic retina for ICAM-1. Normal retinal tissues showed little reactivity.

CONCLUSIONS

Serum chemokines were significantly elevated in patients with at least severe nonproliferative diabetic retinopathy compared with those who had less severe retinopathy. Elevated levels of the chemokines and cell adhesion molecules were also identified in eyes of a donor with ischemic diabetic retinopathy. These findings provide evidence to support the role of inflammation in the pathogenesis of diabetic retinopathy.

EFFECTIVE TRANSSCLERAL DELIVERY OF TWO RETINAL ANTI-ANGIOGENIC MOLECULES

PURPOSE

To evaluate the human transscleral diffusion and intravitreal delivery of carboxyamido-triazole (CAI) and 2-Methoxyestradiol (2ME2).

METHODS

The transscleral diffusion of two retinal antiangiogenic molecules, CAI and 2ME2, was measured in vitro to assess their potential transscleral delivery. Varying concentrations and different solvents of CAI and 2ME2 were placed in the upper compartment of a two-chamber acrylic perfusion apparatus, on the episcleral side of the sclera obtained from human donor eyes. Samples were taken from the lower compartment (uveal side) for up to 24 hours and measured by high performance liquid chromatography.

RESULTS

All three solutions that contained CAI efficiently diffused through the sclera with permeability constants that ranged from 2.8 to 5.5 x 10 cm/s. The scleral permeability constant derived for 2ME2 was 9.96 x 10 cm/s. The permeability constants obtained for both CAI and 2ME2 are similar to each other as well as to permeability constants measured for other small molecules such as fluorescein and dexamethasone fluorescein.

CONCLUSION

Both CAI and 2ME2 traverse the sclera efficiently. These data combined with the reported inhibition of posterior segment neovascularization observed with these two molecules demonstrates that CAI and 2ME2 are good candidate molecules to treat posterior segment neovascularization by local delivery.

The pharmacokinetics of rituximab following an intravitreal injection

Rituximab is a monoclonal antibody directed against the CD20 B-cell antigen and is approved for the treatment of B-cell lymphoma. We investigated the pharmacokinetics of rituximab following intravitreal administration to assess the feasibility of treating primary intraocular lymphoma. Intravitreal injections of rituximab 0.1 ml (1 mg) were performed in rabbits. Drug concentrations in the aqueous and vitreous humor were measured at intervals from 2 to 17 days after administration. The half-life of the total amount of rituximab in the two compartments was calculated to be 4.7 days. The aqueous and vitreous humor drug levels decayed in parallel maintaining an average ratio of approximately seven. Fitting the data to a two-compartment model yielded a clearance from the aqueous humor of 1.2 microl/min. The clearance was less than the reported rate of aqueous humor outflow indicating that elimination by this route could have been sufficient to account for the disappearance of the drug from the eye. The duration of time over which sustained levels of rituximab were achieved suggest that intravitreal administration warrants further investigation as an approach to treating vitreous and anterior chamber infiltrates in patients with primary intraocular lymphoma.

Nonlethal oxidant injury to human retinal pigment epithelium cells causes cell membrane blebbing but decreased MMP-2 activity

PURPOSE

This study was undertaken to determine whether transient or sustained nonlethal oxidant injury can induce RPE cell membrane blebbing and alter RPE expression of matrix metalloproteinase (MMP)-2 and type IV collagen, two molecules that are necessary for regulation of the turnover of the RPE basal lamina.

METHODS

The ARPE-19 cell line stably expressing green fluorescent protein (GFP) targeted to the cell membrane was bleb injured by exposure to myeloperoxidase (MPO; 10 microunits) and H(2)O(2) (100 microM). Sustained (>6 hours) or transient (up to 6 hours) exposure to MPO/H(2)O(2) was evaluated. An MTS assay conversion and cell counts were used to detect cell viability. Supernatants and the cell homogenates were collected from cultured ARPE-19 to assess fluorescent GFP-derived blebs, MMP-2 protein by Western blot, MMP-2 activity by zymography, and type IV collagen accumulation by ELISA. Expression of MMP-2 was examined by real-time RT-PCR with total RNA.

RESULTS

Both sustained and transient exposure of RPE cells to nonlethal oxidant injury upregulated blebbing and increased pro-MMP2 protein, but downregulated the MMP-2 activity released into the supernatant in a time-dependent manner. Only sustained oxidant injury for 24 hours induced an increase in collagen type IV. After removal of transient oxidant exposure, blebbing resolved and RPE MMP-2 activity and protein recovered to normal levels within 48 hours.

CONCLUSIONS

Sustained or transient oxidant injury causes increased cell membrane blebbing but decreased activation of MMP-2. The findings lead to the hypothesis that blebs released in the absence of active MMP-2 may become trapped between the RPE and its basal lamina as sub-RPE deposits, possibly contributing to drusen formation in age-related macular degeneration. Also, the results lead to the postulation that oxidant injury disrupts the cell-specific surface proteases necessary to cleave and activate pro-MMP-2.

Differences in gene expression profiles in dermal fibroblasts from control and patients with age-related macular degeneration elicited by oxidative injury

The pathogenesis of age-related macular degeneration (AMD) is still unknown but there is growing evidence that a combination of both oxidative injury and genetic factors may play a role. One particle hypothesis proposes that dysregulation of multiple genes in response to an oxidative injury could contribute to the development of AMD. While direct examination of ocular cells from AMD patients is difficult, AMD also appears to have a systemic component. Therefore, as is the case with other central nervous diseases, peripheral sites may also manifest any underlying genetic abnormalities. For the present study, biopsy-derived fibroblasts from 4 patients with the early form and 4 patients with the late form of AMD and 3 age-matched control patients were grown in culture and treated with a nonlethal dose of the oxidative stimulus menadione. Gene expression patterns were quantitatively and qualitatively examined using Human Genome U95A GeneChips (Affymetrix) and verified by real-time PCR analysis. In response to the oxidative injury 755 genes were found to be upregulated at least twofold in one of the patients groups. Cluster analysis of expression profiles detected six patterns of dysregulation initiated by oxidative injury specific for the disease groups (98 genes total). Clusters of genes dysregulated by the sublethal oxidative injury in either early and/or late AMD groups were further categorized by overrepresentation of GO "biological process" categories using Expression Analysis Systematic Explorer (EASE) software. This approach demonstrated that four major functional gene groups including inflammatory/innate immune response, transcriptional regulation, cell cycle, and proliferation were significantly overrepresented (Fisher test ranging from 0.0393 to 0.00018) in both AMD patients groups in response to the oxidative injury. Despite the small number of patients in the study, specific biological and statistical differences in gene expression profiles between control and AMD patients were identified but only in the presence of an environmental stimulus.