Emerging roles for antiangiogenesis factors in management of ocular disease

A Paradigm Shift in the Management Approaches of Proliferative Diabetic Retinopathy: Role of Anti-VEGF Therapy

Diabetic retinopathy (DR) is considered one of the leading causes of vision loss globally. It principally causes upregulation of pro-angiogenic, proinflammatory, and vascular permeability factors such as vascular endothelial growth factor (VEGF), leading to neovascularisation. The advanced stage of DR or proliferative diabetic retinopathy (PDR) is of more concern, as it leads to vitreous haemorrhage and traction retinal detachment. Various risk factors associated with PDR include hyperglycemia, hypertension, neuropathy, dyslipidemia, anaemia, nephropathy, and retinal complications of drugs used for diabetes. Current management approaches for PDR have been stratified and involve pan-retinal photocoagulation, vitrectomy, and anti-VEGF agents. Given the emerging role of anti-VEGF agents as a favourable adjunct or alternative therapy, they have a critical role in the management of PDR. The review emphasises current management approaches for PDR focusing on anti-VEGF therapy. The review also highlights the risk/benefit evaluation of the various approaches employed for PDR management in various clinical scenarios.

Effectiveness of prophylactic intravitreal bevacizumab injection to proliferative diabetic retinopathy patients with elevated preoperative intraocular VEGF in preventing complications after vitrectomy

Purpose

This study aimed to elucidate the effects of intravitreal bevacizumab (IVB) injections for the prevention of post-vitrectomy complications in proliferative diabetic retinopathy (PDR) patients with elevated vitreous vascular endothelial growth factor (VEGF) concentration.

Design

Prospective case series.

Methods

Thirty-three patients (42 eyes) with PDR who underwent primary vitrectomy in the Department of Ophthalmology, Tokyo Medical University Hospital were studied. We measured VEGF concentrations in vitreous humor collected at the time of vitrectomy using ELISA. IVB injections were performed after vitrectomy in patients with vitreous VEGF levels exceeding 1,000 pg/mL. New bleeding occurring within 1 month of vitrectomy was defined as early vitreous hemorrhage (VH).

Main outcome measure

The incidence of complications after vitrectomy including postoperative early VH.

Results

IVB injections were administered to 11 eyes (26%) with vitreous VEGF concentrations exceeding 1,000 pg/mL. None of the 11 eyes that received an IVB injection developed early VH. Among 31 eyes (74%) with vitreous VEGF concentrations lower than 1,000 pg/mL, two eyes (6%) developed early VH after vitrectomy.

Conclusions

Prophylactic IVB injections administered to patients with elevated preoperative intraocular VEGF concentrations were effective in preventing post-vitrectomy early VH.

The Question of a Role for Statins in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible central vision loss in patients over the age of 65 years in industrialized countries. Epidemiologic studies suggest that high dietary fat intake is a risk factor for the development and progression of both vascular and retinal disease. These, and other associations, suggest a hypothesis linking elevated cholesterol and AMD progression. It follows, therefore, that cholesterol-lowering medications, such as statins, may influence the onset and progression of AMD. However, the findings have been inconclusive as to whether statins play a role in AMD. Due to the significant public health implications of a potential inhibitory effect of statins on the onset and progression of AMD, it is important to continually evaluate emerging findings germane to this question.

Vertebrate embryos as tools for anti-angiogenic drug screening and function

The development of new angiogenic inhibitors highlights a need for robust screening assays that adequately capture the complexity of vessel formation, and allow for the quantitative evaluation of the teratogenicity of new anti-angiogenic agents. This review discusses the use of screening assays in vertebrate embryos, specifically focusing upon chicken and zebrafish embryos, for the detection of anti-angiogenic agents.

Systemic safety of intravitreal anti-vascular endothelial growth factor agents in age-related macular degeneration

PURPOSE OF REVIEW

The purpose of review is to summarize the literature addressing nonocular adverse events in patients with neovascular age-related macular degeneration treated with intravitreal vascular endothelial growth factor (VEGF) inhibitors and to present possible mechanisms of effect.

RECENT FINDINGS

The incidence of overall nonocular serious adverse events varied from 0 to 39.3% and nonocular adverse events ranged from 0 to 86.9%. Few studies have reported a significant association between use of intravitreal anti-VEGF agents and overall incidence of adverse events, stroke, myocardial infarction, nonocular hemorrhage and death, with overall greater concern in patients treated with bevacizumab. Additionally, history of stroke or other arterial thromboembolic event may be a risk factor for future stroke in patients treated with intravitreal anti-VEGF agents. Theories explaining the mechanisms of increased risk of nonocular adverse events secondary to anti-VEGF agent use surround the necessity of VEGF for the normal functioning of the endothelium and the damage incurred with use of anti-VEGF agents.

SUMMARY

Current data are insufficient to definitively conclude that intravitreal anti-VEGF agents are safe, although there is a trend toward an overall favorable systemic safety profile. Caution should be exerted in patients with a history of cardiovascular disease, as these patients may be at greater risk for nonocular serious adverse events.

Shared mechanism of teratogenicity of anti-angiogenic drugs identified in the chicken embryo model

Angiogenesis, the formation of new blood vessels, is essential for tumor growth, stabilization and progression. Angiogenesis inhibitors are now widely used in the clinic; however, there are relatively few published studies on the mechanism of their presumed teratogenic effects. To address this issue, we screened a variety of angiogenesis inhibitors in developing zebrafish and chicken embryo models to assess for developmental defects and potential teratogenic effects. We confirmed previous reports that sunitinib, sorafenib and TNP-470 are teratogenic and demonstrate that axitinib, pazopanib, vandetanib, and everolimus are also teratogens in these models. A dose response study identified the drugs inhibit HUVEC cell proliferation in vitro, and also target the developing blood vessels of embryos in vivo. This provides further evidence for the potential risk of fetal toxicity when using these drugs in a clinical setting, and emphasizes the importance of the development and maintenance of the vasculature in the embryo. We conclude that angiogenesis inhibitors, regardless of the molecular target, are teratogenic when exposed to chicken embryos.

Association of the polymorphism Y402H in the CFH gene with response to anti-VEGF treatment in age-related macular degeneration: a systematic review and meta-analysis

To explore whether the complement factor H (CFH) polymorphism rs1061170/Y402H is associated with responsiveness to antivascular endothelial growth factor (VEGF) agents in age-related macular degeneration (AMD). We reviewed the English literature to examine the association between the polymorphism rs1061170/Y402H of the CFH gene and responsiveness to treatment with anti-VEGF drugs in AMD patients. A meta-analysis of eligible studies was also performed. Pooled odds ratios (ORs) and 95% CIs were estimated using Stata V.12.0. Statistical heterogeneity was measured using Q-statistic testing. Fourteen relevant studies including a total of 2963 AMD patients were eligible. In AMD patients without a treatment history, individuals carrying the rs1061170/Y402H TT genotype were more likely to achieve a better outcome (OR = 1.932, 95% CI = 1.125-3.317, p = 0.017) than those carrying the CC genotype. The polymorphism rs1061170/Y402H might be a genetic predictor of treatment response to anti-VEGF therapy in AMD patients. Further prospective research including a larger number of patients is needed to validate this finding.

Novel investigational vascular endothelial growth factor (VEGF) receptor antagonists for psoriasis

INTRODUCTION

Affecting 1 million people in the UK, psoriasis is a commonly diagnosed inflammatory disease arising from autoimmune processes that are triggered by environmental factors in genetically susceptible individuals. The pathophysiology of psoriasis has been widely studied and there is evidence that angiogenesis is a key component.

AREAS COVERED

In this review the role of vascular endothelial growth factor-A (VEGF), as a key angiogenic mediator in psoriasis pathogenesis is discussed. VEGF is found in higher levels in plaques, normal skin and plasma of patients with psoriasis. The level of VEGF also fluctuates in accordance with disease activity and in response to conventional treatments. There are several VEGF inhibitors currently licenced for use; primarily in the fields of oncology and there are case reports of patients being treated with these therapies for metastatic cancer who have demonstrated significant improvement in their psoriasis. VEGF inhibitory agents have suggested promising utility for the treatment of psoriasis following animal studies.

EXPERT OPINION

VEGF may represent a novel treatment target in psoriasis. However, VEGF inhibitors can cause significant side effects such as hypertension and left ventricular dysfunction. The risks of treatment must be carefully evaluated before VEGF inhibitors are trialled or advocated for psoriasis.

Diffusion of anti-VEGF injections in the Portuguese National Health System

OBJECTIVES

To analyse the temporal and geographical diffusion of antivascular endothelial growth factor (anti-VEGF) interventions, and its determinants in a National Health System (NHS).

SETTING

NHS Portuguese hospitals.

PARTICIPANTS

All inpatient and day cases related to eye diseases at all Portuguese public hospitals for the period 2002-2012 were selected on the basis of four International Classification of Diseases 9th revision, Clinical Modification (ICD-9-CM) codes for procedures: 1474, 1475, 1479 and 149.

PRIMARY AND SECONDARY OUTCOME MEASURES

We measured anti-VEGF treatment rates by year and county. The determinants of the geographical diffusion were investigated using generalised linear modelling.

RESULTS

We analysed all hospital discharges from all NHS hospitals in Portugal (98,408 hospital discharges corresponding to 57,984 patients). National rates of hospitals episodes for the codes for procedures used were low before anti-VEGF approval in 2007 (less than 12% of hospital discharges). Between 2007 and 2012, the rates of hospital episodes related to the introduction of anti-VEGF injections increased by 27% per year. Patients from areas without ophthalmology departments received fewer treatments than those from areas with ophthalmology departments. The availability of an ophthalmology department in the county increased the rates of hospital episodes by 243%, and a 100-persons greater density per km(2) raised the rates by 11%.

CONCLUSIONS

Our study shows a large but unequal diffusion of anti-VEGF treatments despite the universal coverage and very low copayments. The technological innovation in ophthalmology may thus produce unexpected inequalities related to financial constraints unless the implementation of innovative techniques is planned and regulated.

Current perspectives on ranibizumab

Background

This review summarizes the Phase III studies addressing intravitreal ranibizumab treatment in patients with neovascular age-related macular degeneration (AMD), macular edema (ME) from retinal vein occlusion (RVO), and diabetic ME (DME).

Results

The data from 12 major Phase III studies: six studies in patients with neovascular AMD, two studies in patients with ME from RVO, and four studies in patients with DME demonstrate significant improvement in vision in patients undergoing treatment with intravitreal ranibizumab over patients receiving no treatment or receiving only grid laser. These effects are achieved with low incidences of ocular and nonocular adverse events.

Conclusion

Intravitreal ranibizumab is a highly effective and safe therapy for improving vision and reducing vision loss in patients with neovascular AMD, ME from RVO, and DME. Patients generally require long-term treatment although some data show that frequency of treatment necessary to maintain visual outcomes decreases over time.

Pharmacogenomics of response to anti-VEGF therapy in exudative age-related macular degeneration

PURPOSE

To determine whether there is an association between response to intravitreal anti-vascular endothelial growth factor agents and genotype in patients with neovascular age-related macular degeneration.

METHODS

Analysis of the current literature evaluating pharmacogenetics of treatment response in patients with neovascular age-related macular degeneration.

RESULTS

Studies have demonstrated associations between various genotypes and response to intravitreal anti-vascular endothelial growth factor agents. Lower-risk genotypes of the CFH, ARMS2, HTRA1, and VEGF-A genes may be associated with improved visual outcomes. Additionally, frequency of injections may be associated with certain genotypes.

CONCLUSION

Genetic background may influence an individual's response to treatment of neovascular age-related macular degeneration. Further studies to investigate biologic pathways of neovascular age-related macular degeneration and gene products that are directly involved might lead to better understanding of contribution of various genes to treatment response.

[Off-label use of intravitreal bevacizumab for severe retinopathy of prematurity]

OBJECTIVE

To examine the quality of evidence and the variability in the off-label use of intravitreal bevacizumab for retinopathy of prematurity (ROP).

METHODS

A wide review of the literature was performed using Pubmed, Medline, and Cochrane database, using the words vascular endothelial growth factor (VEGF), retinopathy of prematurity, treatment and bevacizumab.

RESULTS

Case reports, case series, reviews, one sistematic review and one randomized controlled trial were found on the use of intravitreal bevacizumab in severe ROP, as monotherapy or combined with láser and/or vitrectomy.

CONCLUSIONS

The results shown on the use of intravitreal bevacizumab in ROP stage 3+ in zone I or in aggressive posterior ROP are promising. However, uncertainty remains regarding its maximum tolerable dose in the neonatal group, its ocular and systemic safety profile, or its efficacy and bioactivity in a developing child. This report found no significant differences in the recurrence rates of ROP stage 3+ in zone II in patients treated with intravitreal bevacizumab monotherapy in comparison to láser, although the latter is the best option due to long-term safety and efficacy. The use of intravitreal bevacizumab is not indicated in stages 1 and 2 of ROP as the risk of severe visual loss is low and VEFG is necessary for normal retinal vessel development. On the other hand, the use of intravitreal bevacizumab would be contraindicated in stages 4 and 5 because the retinal detachment is accelerated.

The ABCs of RVO: a review of retinal venous occlusion

Retinal vein occlusions are important causes of loss of vision; indeed, they are the second most common retinal vascular disease, following diabetic retinopathy. For this reason alone, primary eye-care providers must be well versed in diagnosis and management. Risk factors, though not universally agreed upon, include but are not limited to advancing age, systemic hypertension, arteriolarsclerosis, diabetes, hyperlipidaemia, blood hyperviscosity, thrombophilia, ocular hypertension and glaucoma. Typically, visual loss is secondary to macular oedema and/or retinal ischaemia. Treatment modalities have included observation, systemic thrombolysis and haemodilution, radial optic neurotomy, chorioretinal anastomosis, vitrectomy, laser photocoagulation and intravitreal injection of anti-inflammatory and, most recently, anti-vascular endothelial growth factors.

Vascular endothelial growth factor inhibitors: investigational therapies for the treatment of psoriasis

Psoriasis is a common inflammatory autoimmune condition in which environmental factors and genetic predisposition contribute to the development of disease in susceptible individuals. Angiogenesis is known to be a key pathogenic feature of psoriasis. Local and systemic elevation of vascular endothelial growth factor (VEGF)-A has been demonstrated in the skin and plasma of patients with psoriasis and is known to correlate with improvement following some traditional psoriasis treatments. A number of VEGF inhibitors are licensed for the treatment of malignancies and eye disease and isolated case reports suggest that some individuals with psoriasis may improve when exposed to these agents. The small number of cases and lack of unified reporting measures makes it difficult to draw generalizations and underline the heterogeneity of psoriasis as a disease entity. Though not yet licensed for the treatment of psoriasis in humans, experimental data supports the potential of VEGF inhibitors to influence relevant aspects of human cell biology (such as endothelial cell differentiation) and to improve animal models of skin disease. Given the multi-factorial nature of psoriasis it is unlikely that VEGF inhibitors will be effective in all patients, however they have the potential to be a valuable addition to the therapeutic arsenal in selected cases. Current VEGF inhibitors in clinical use are associated with a number of potentially serious side effects including hypertension, left ventricular dysfunction, and gastrointestinal perforation. Such risks require careful consideration in psoriasis populations particularly in light of growing concerns linking psoriasis to increased cardiovascular risk.