Extended duration strategies for the pharmacologic treatment of diabetic retinopathy: current status and future prospects

Orally Delivered Connexin43 Hemichannel Blocker, Tonabersat, Inhibits Vascular Breakdown and Inflammasome Activation in a Mouse Model of Diabetic Retinopathy

Diabetic retinopathy (DR), a microvascular complication of diabetes, is associated with pronounced inflammation arising from the activation of a nucleotide-binding and oligomerization domain-like receptor (NLR) protein 3 (NLRP3) inflammasome. Cell culture models have shown that a connexin43 hemichannel blocker can prevent inflammasome activation in DR. The aim of this study was to evaluate the ocular safety and efficacy of tonabersat, an orally bioavailable connexin43 hemichannel blocker, to protect against DR signs in an inflammatory non-obese diabetic (NOD) DR mouse model. For retina safety studies, tonabersat was applied to retinal pigment epithelial (ARPE-19) cells or given orally to control NOD mice in the absence of any other stimuli. For efficacy studies, either tonabersat or a vehicle was given orally to the inflammatory NOD mouse model two hours before an intravitreal injection of pro-inflammatory cytokines, interleukin-1 beta, and tumour necrosis factor-alpha. Fundus and optical coherence tomography images were acquired at the baseline as well as at 2- and 7-day timepoints to assess microvascular abnormalities and sub-retinal fluid accumulation. Retinal inflammation and inflammasome activation were also assessed using immunohistochemistry. Tonabersat did not have any effect on ARPE-19 cells or control NOD mouse retinas in the absence of other stimuli. However, the tonabersat treatment in the inflammatory NOD mice significantly reduced macrovascular abnormalities, hyperreflective foci, sub-retinal fluid accumulation, vascular leak, inflammation, and inflammasome activation. These findings suggest that tonabersat may be a safe and effective treatment for DR.

Essentials of a Robust Deep Learning System for Diabetic Retinopathy Screening: A Systematic Literature Review

This systematic review was performed to identify the specifics of an optimal diabetic retinopathy deep learning algorithm, by identifying the best exemplar research studies of the field, whilst highlighting potential barriers to clinical implementation of such an algorithm. Searching five electronic databases (Embase, MEDLINE, Scopus, PubMed, and the Cochrane Library) returned 747 unique records on 20 December 2019. Predetermined inclusion and exclusion criteria were applied to the search results, resulting in 15 highest-quality publications. A manual search through the reference lists of relevant review articles found from the database search was conducted, yielding no additional records. A validation dataset of the trained deep learning algorithms was used for creating a set of optimal properties for an ideal diabetic retinopathy classification algorithm. Potential limitations to the clinical implementation of such systems were identified as lack of generalizability, limited screening scope, and data sovereignty issues. It is concluded that deep learning algorithms in the context of diabetic retinopathy screening have reported impressive results. Despite this, the potential sources of limitations in such systems must be evaluated carefully. An ideal deep learning algorithm should be clinic-, clinician-, and camera-agnostic; complying with the local regulation for data sovereignty, storage, privacy, and reporting; whilst requiring minimum human input.

Emerging corticosteroid delivery platforms for treatment of diabetic macular edema

INTRODUCTION

Diabetic macular edema (DME) is a leading cause of vision impairment. Low-grade inflammation is thought to play a critical role in its pathogenesis. Although vascular endothelial growth factor inhibitors are used first-line, not all eyes with DME respond optimally and may respond better to corticosteroids. Currently corticosteroids for DME are given intravitreally and require regular monitoring. There is an unmet need for longer lasting therapies and/or effective noninvasive therapies such as those given via oral or topical routes.

AREAS COVERED

This review discusses emerging corticosteroid delivery platforms for DME treatment. A literature search of investigational novel therapeutic steroid delivery platform in DME was conducted. Results are presented from preclinical, phase 1,2 & 3 clinical trials of various drug delivery systems using new technologies such as Solubilizing Nanoparticle technology, Mucus Penetrating Particles technology and Particle Replication In Non-wetting Templates. These new platforms aim to deliver corticosteroids effectively via topical, episcleral, subtenon, oral, and intravitreal routes.

EXPERT OPINION

These novel drug delivery platforms have the potential to lead to noninvasive or minimally invasive therapies and may overcome the shortcomings of current pharmacotherapy. However, larger comparative trials are needed for these agents to be added to the current armamentarium in DME management.

Discontinuous to continuous therapy for persistent diabetic macular edema leads to reduction in treatment frequency

OBJECTIVE

To evaluate, in the setting of persistent diabetic macular edema, the impact that continuous fluocinolone acetonide delivery has on treatment burden, visual acuity, central retinal thickness, and intraocular pressure.

MATERIALS AND METHODS

A single-center, retrospective, cohort study of patients with persistent diabetic macular edema, previously treated with anti-vascular endothelial growth factor injections, dexamethasone implants, or focal laser, who were subsequently treated with fluocinolone acetonide was conducted. All retinal visits were analyzed prior to fluocinolone acetonide, until the most recent follow-up visit. Primary outcomes were pre- and post-fluocinolone acetonide changes in the best-corrected visual acuity and number of treatments required for diabetic macular edema. Secondary outcomes included changes in the central retinal thickness and intraocular pressure.

RESULTS

A total of 19 eyes with persistent diabetic macular edema were included and followed for a mean (SD) of 399.3 (222.9) days. Post-fluocinolone acetonide, the mean best-corrected visual acuity improved by 0.4 ETDRS letters for all eyes (p = 0.895) and the central retinal thickness decreased by 34.2 µm (p = 0.077). After fluocinolone acetonide, the number of treatments decreased from an average of one treatment every 2.7 months to one every 6 months (p = 0.009). Furthermore, post-fluocinolone acetonide, 10/19 eyes (52.6%) did not require additional treatment due to a dry macula, and those who did experienced a non-statistically significant reduction of treatments, from one every 2.6 months pre-fluocinolone acetonide, to one every 2.8 months post-fluocinolone acetonide (p = 0.622).

CONCLUSIONS

In the setting of persistent diabetic macular edema, fluocinolone acetonide significantly reduces the therapeutic burden, while maintaining best-corrected visual acuity and improving the central retinal thickness. In patient-centered discussions, judiciously employing fluocinolone acetonide should be performed to mitigate this therapeutic burden for patients.

Effects of Intravitreal Bevacizumab Therapy in Patients with Proliferative Diabetic Retinopathy

INTRODUCTION

Diabetes mellitus (DM) stands out as one of the chronic diseases with the highest morbidity and mortality rates worldwide. Among the many complications of DM, diabetic retinopathy (DR) is one of the causes of blindness in patients aged between 20 and 64 years. At least 90% of the new cases showed to have the retinal structure and function restored when proper treatment was provided.

AIM

To evaluate the efficacy of the antiangiogenic bevacizumab in the treatment of DR according not only to the clinical laboratory parameters for glycated hemoglobin (HbA1C) and capillary glycemia but also to the ophthalmological parameters for optical coherence tomography (OCT) and best-corrected visual acuity (BCVA).

PATIENTS AND METHODS

A total of 11 individuals were included and followed up for 12 months after 3 administrations of bevacizumab.

RESULTS

Upon associating the ophthalmological and laboratory variables throughout the treatment, no significant alterations could be seen regarding the analyzed variables. However, it was observed that HbA1c values and the total leukocyte count negatively interfered with the treatment response.

CONCLUSION

The current study showed that HbA1c values and the amount of leukocytes negatively interfere with the therapeutic response. Therefore, laboratory analyses of these parameters are recommended for diabetic patients undergoing the above-mentioned treatment.

Predictive capacity of baseline hyperreflective dots on the intravitreal dexamethasone implant (Ozurdex®) outcomes in diabetic macular edema: a multicenter study

PURPOSE

The purpose of this study is to evaluate the predictive capacity of the baseline hyperreflective dots (HRDs) on the functional and anatomical response in patients with diabetic macular edema (DME). Additionally, we assessed the impact of the intravitreal dexamethasone (DEX) implant on the functional and anatomic outcomes.

METHODS

Retrospective, multicenter study. The number of HRDs was graded in four different stages: [A] none HRDs; [B] few, 1-10 HRDs; [C] moderate, 11-20 HRDs; and [D] many, ≥ 21 HRDs. For statistical purposes, groups A and B were combined [scarce HRDs (S-HRDs)] and group D was renamed as [abundant HRDs (A-HRDs)]. The primary endpoints were the mean change in best corrected visual acuity (BCVA) and central macular thickness (CMT) according to baseline HRD stage.

RESULTS

One hundred eyes from one hundred patients were included in the study. Mean BCVA significantly improved from 52.9 (50.0 to 55.8) letters ETDRS at baseline to 57.2 (54.0 to 60.4) letters at month 6, p = 0.0039. There were no significant differences between the S-HRDs and A-HRD study groups in BCVA. As compared to baseline, CMT reduction was 106.3 (59.8 to 152.7) μm and 94.2 (34.7 to 153.7) μm in S-HRDs and A-HRD groups, respectively (p < 0.0001 each, respectively). Twenty-three (65.7%) and 18 (62.1%) eyes achieved a CMT reduction ≥ 10% in the S-HRD and A-HRD groups, respectively, p = 0.7640. DEX implant significantly reduced the presence of outer nuclear layer (ONL) disruptions (p = 0.0010).

CONCLUSIONS

The number of HRDs did not influence either functional or anatomic outcomes. DEX implant significantly decreases the number of eyes with ONL disruptions, which might improve retinal integrity.

Adipose stem cells and their paracrine factors are therapeutic for early retinal complications of diabetes in the Ins2Akita mouse

BACKGROUND

Early-stage diabetic retinopathy (DR) is characterized by neurovascular defects. In this study, we hypothesized that human adipose-derived stem cells (ASCs) positive for the pericyte marker CD140b, or their secreted paracrine factors, therapeutically rescue early-stage DR features in an Ins2Akita mouse model.

METHODS

Ins2Akita mice at 24 weeks of age received intravitreal injections of CD140b-positive ASCs (1000 cells/1 μL) or 20× conditioned media from cytokine-primed ASCs (ASC-CM, 1 μL). Age-matched wildtype mice that received saline served as controls. Visual function experiments and histological analyses were performed 3 weeks post intravitreal injection. Biochemical and molecular analyses assessed the ASC-CM composition and its biological effects.

RESULTS

Three weeks post-injection, Ins2Akita mice that received ASCs had ameliorated decreased b-wave amplitudes and vascular leakage but failed to improve visual acuity, whereas Ins2Akita mice that received ASC-CM demonstrated amelioration of all aforementioned visual deficits. The ASC-CM group demonstrated partial amelioration of retinal GFAP immunoreactivity and DR-related gene expression but the ASC group did not. While Ins2Akita mice that received ASCs exhibited occasional (1 in 8) hemorrhagic retinas, mice that received ASC-CM had no adverse complications. In vitro, ASC-CM protected against TNFα-induced retinal endothelial permeability as measured by transendothelial electrical resistance. Biochemical and molecular analyses demonstrated several anti-inflammatory proteins including TSG-6 being highly expressed in cytokine-primed ASC-CM.

CONCLUSIONS

ASCs or their secreted factors mitigate retinal complications of diabetes in the Ins2Akita model. Further investigation is warranted to determine whether ASCs or their secreted factors are safe and effective therapeutic modalities long-term as current locally delivered therapies fail to effectively mitigate the progression of early-stage DR. Nonetheless, our study sheds new light on the therapeutic mechanisms of adult stem cells, with implications for assessing relative risks/benefits of experimental regenerative therapies for vision loss.

Long-term efficacy and safety profile of multiple injections of intravitreal dexamethasone implant to manage diabetic macular edema: A systematic review of real-world studies

INTRODUCTION

Systematic review of real-world studies about repeated dexamethasone intravitreal implant (DEXi) 0.7 mg in diabetic macular edema management, in order to identify the effective window of time occurring between injections, the critical evaluation of efficacy of the treatment, and the relative long-term safety in the real life setting.

METHODS

Literature databases such as PubMed, SCOPUS, and EMBASE were used to identify reports including DEX implant injections.

RESULTS

Twenty-one peer-reviewed publications were identified. DEX implants retreatment was considered on a pro re nata (PRN) basis at any time or starting from month three or four. About 1/3 of the eyes were retreated before six months from first injection (range 0-86.7%). Mean retreatment average time was 5.3 ± 0.9 months, with an estimated average of 1.3 injections each six months. There was no statistical correlation between average retreatment time and incidence of adverse events or other variables investigated. Limited safety issues related to implants number have been found, suggesting an overall good tolerance of long-term DEXi.

CONCLUSIONS

Comprehensive evaluation of real-world data suggests an average DEXi duration close to five months, following a PRN treatment strategy, including about 1/3 of patients. Repeated DEXi administration revealed an acceptable long-term efficacy/safety ratio.

Potential effect on molecular pathways in different targeted genes in the VEGF family in retina - From the genomic point of view

This study's goal is to determine similarities and differences in the molecular pathways or potential functions of the various targeted regions or genes of the Vegf family-VegfA, VegfB, VegfC, and Pgf-using the BXD genetic reference panel. Data from whole genome expression profiles of retinas from the well-characterized mouse recombinant inbred (RI) strain population derived from C57BL/6J X DBA/2J (BXD) were analyzed. Multiple analytical tools and statistical strategies were used to investigate the expression level. The expression Quantitative Trait Loci (QTLs) of these probes were mapped and compared. Our data showed that VegfA2 has the highest expression levels among all probes of Vegf genes. The expression levels of Vegf family genes are not significantly correlated. In the overall comparison, expression levels of VegfA1 and VegfA2 are positively correlated (R = 0.540). The expression levels of VegfB and VegfC are weakly correlated (R = 0.360). VegfC is also weakly correlated with the expression levels of Pgf (R = 0.324). The interaction of VegfB- and VegfA2-associated 50a2 genes was very weak (R50 ab = 0.3129). The interaction of top VegfB-associated 50b genes with VegfA2 has a reciprocal negative impact (R50ba = -0.42758). The VegfC-associated top 50c genes are strongly correlated with VegfB (R50 cb = 0.8159), while they are negatively correlated with VegfA2 (R50ca = -0.1450). Expression quantitative trait loci (eQTL) analysis suggested that the regulatory mechanisms for the expression levels of these genes in the Vegf family are different from each other. The expression level of VegfA associates with a group of genes that are not associated with other genes in the Vegf family.

Therapeutic Effect of Anti-VEGF for Age-Related Macular Degeneration in the Untreated Fellow Eye

Intravitreal injections of antivascular endothelial growth factor (anti-VEGF) agents have been reported to occasionally produce a therapeutic effect in the uninjected fellow eye. Here, three patients with bilateral neovascular age-related macular degeneration are presented. In all three patients, unilateral anti-VEGF injection resulted in bilateral reduction of macular thickness as measured by spectral domain optical coherence tomography.

Current Advances in Pharmacotherapy and Technology for Diabetic Retinopathy: A Systematic Review

Diabetic retinopathy (DR) is classically defined by its vascular lesions and damage in the neurons of the retina. The cellular and clinical elements of DR have many features of chronic inflammation. Understanding the individual cell-specific inflammatory changes in the retina may lead to novel therapeutic approaches to prevent vision loss. The systematic use of available pharmacotherapy has been reported as a useful adjunct tool to laser photocoagulation, a gold standard therapy for DR. Direct injections or intravitreal anti-inflammatory and antiangiogenesis agents are widely used pharmacotherapy to effectively treat DR and diabetic macular edema (DME). However, their effectiveness is short term, and the delivery system is often associated with adverse effects, such as cataract and increased intraocular pressure. Further, systemic agents (particularly hypoglycemic, hypolipidemic, and antihypertensive agents) and plants-based drugs have also provided promising treatment in the progression of DR. Recently, advancements in pluripotent stem cells technology enable restoration of retinal functionalities after transplantation of these cells into animals with retinal degeneration. This review paper summarizes the developments in the current and potential pharmacotherapy and therapeutic technology of DR. Literature search was done on online databases, PubMed, Google Scholar, clinitrials.gov, and browsing through individual ophthalmology journals and leading pharmaceutical company websites.

Clinical and Biochemical Associations with Diabetic Retinopathy in Male Patients in the Gaza Strip

BACKGROUND

There are limited data on the prevalence and risk factors for diabetic retinopathy (DR) in the Gaza Strip.

OBJECTIVE

To assesses clinical and biochemical associated with DR in males with type 2 diabetes mellitus (T2DM) in the Gaza Strip.

METHODS

One hundred and fifty males with T2DM from the Gaza Strip underwent a questionnaire interview, serum biochemical analysis, and assessment of their previous urine and blood results.

RESULTS

The prevalence of DR was 24.7%. The duration of diabetes and prevalence of neuropathy, nephropathy, cardiovascular disease, and recurrent infections were significantly higher among patients with DR compared with those without DR (p < 0.05). Serum urea, creatinine, glucose, cholesterol, and low-density lipoprotein cholesterol were significantly elevated, whilst eGFR and high-density lipoprotein cholesterol were significantly lower in patients with DR compared with patients without DR (p < 0.05). Urinary albumin concentration and albumin creatinine ratio (ACR) was higher in patients with DR. ACR correlated significantly with the duration of T2DM (r = 0.311, p < 0.001), glucose (r = 0.479, p < 0.001), urea (r = 0.337, p < 0.001), creatinine (r = 0.275, p = 0.001), and GFR (r = -0.275, p < 0.001).

CONCLUSION

These data show a high prevalence of DR in an unselected cohort of patients with T2DM and relationships to modifiable risk factors in Gaza.

Recurrent Diabetic Macular Edema: What to Do

Diabetic macular edema (DME) is a leading cause of blindness in the working population. Herein, we report the case of a patient with recurrent DME for about 6 years, uncontrolled by several medical and surgical treatments, that was successfully treated with a single sustained-release fluocinolone acetonide intravitreal implant in her right eye. The affected eye had presented a visual acuity of 2/10 and a central macular thickness of 488 µm prior to the injection. After treatment with the fluocinolone acetonide intravitreal implant, the patient's right eye presented an improvement in best corrected visual acuity to 6/10 and a reduction of central macular thickness to 198 µm. These functional and anatomical results were continuous and sustained during a follow-up period of more than 12 months, and with an acceptable and manageable safety profile. These results show that fluocinolone acetonide intravitreal implantation is an effective treatment option in DME and should be considered in the DME treatment pathway.

Therapeutic Options in Refractory Diabetic Macular Oedema

Diabetic macular oedema (DMO) results from alterations of several biochemical pathways in diabetic eyes. Centre-involving DMO is an important cause of visual loss in diabetes. Anti-vascular endothelial growth factor agents are now the mainstay of centre-involving DMO treatment. Oedema that does not achieve optimal response to these agents occurs in a sizeable proportion of eyes and is called refractory or persistent DMO. Management of refractory DMO is challenging. In this paper, the pathophysiology of DMO, and the definitions used in various studies are summarised. Therapeutic options for refractory DMO management including corticosteroids, laser, combination therapies, and surgery are explored. Novel agents on the horizon for DMO control that are being investigated at present are discussed as well. A literature review was performed and a summary of the research studies for each of the agents is provided in order to guide the reader regarding the existing evidence for their application in DMO. Importance of early recognition of disease and prompt treatment to achieve best visual outcome is discussed. Utility of optical coherence tomography to guide disease diagnosis and monitoring is highlighted. An algorithmic approach for DMO management is described. Finally, the impact that personalized medicine and genetics might have on DMO management is assessed.

Real-Life ILUVIEN (Fluocinolone Acetonide) Case Study: Rapid Drying of the Macula and Improved Vision within 2 Years after Therapy Initiation

IMPORTANCE

A case showing sustained structural and functional responses 2 years after a single treatment with ILUVIEN (0.2 µg/day fluocinolone acetonide, FAc) despite suboptimal responses to ranibizumab.

OBSERVATIONS

A 68-year-old female patient with diabetic macular oedema (DME) from type 2 diabetes mellitus was first diagnosed in October 2010 and had a baseline visual acuity (VA) of 46 Early Treatment Diabetic Retinopathy Study (ETDRS) letters in the left eye. Central foveal thickness (CFT) was 712 microns. The patient was treated with 11 intravitreal injections of ranibizumab (5 in combination with a small-interfering RNA agent), and by March 2014, VA and CFT were largely unchanged (55 ETDRS letters and 774 microns). The patient was treated with ILUVIEN as she had a pseudophakic lens and a clearly suboptimal response to the prior therapy with ranibizumab. An implant releasing FAc at a dosage of 0.2 µg/day was administered in March 2014, and the optical coherence tomography indicated that the macula was dry after 7 days (CFT was below 300 microns). This was sustained at 6, 12, and 24 months after the treatment. VA improved by 5 letters within 7 days and by 15 letters within 14 days, and this was maintained after 24 months. Throughout the duration of this study, the intraocular pressure was ≤22 mm Hg, and no glaucoma medication was administered.

CONCLUSIONS AND RELEVANCE

In real-life UK practice, this DME patient showed a suboptimal response to multiple intravitreal injections of ranibizumab. When subsequently treated with a single injection of ILUVIEN, there were large and rapid improvements in VA and CFT that were maintained for the following 2 years.

Update on corticosteroids for diabetic macular edema

Diabetic macular edema (DME) remains an important cause of visual loss. Although anti-vascular endothelial growth factor (VEGF) agents are generally used as first-line treatments for patients with center-involving DME, there is an important role for corticosteroids as well. Corticosteroids may be especially useful in pseudophakic patients poorly responsive to anti-VEGF therapies, in patients wishing to reduce the number of required injections, and in pregnant patients. Intravitreal triamcinolone acetonide has been used for many years but is not approved for this indication. An extended-release bioerodable dexamethasone delivery system and an extended-release nonbioerodable fluocinolone acetonide insert have both achieved regulatory approval for the treatment of DME. All intravitreal corticosteroids are associated with risks of cataract progression, elevation of intraocular pressure, and endophthalmitis. There is no current consensus regarding the use of corticosteroids, but they are valuable for selected patients with center-involving DME.