There are two major types of ocular neovascularization that affect the retina, retinal neovascularization (NV) and subretinal or choroidal NV. Retinal NV occurs in a group of diseases referred to as ...ischemic retinopathies in which damage to retinal vessels results in retinal ischemia. Most prevalent of these are diabetic retinopathy and retinal vein occlusions. Subretinal and choroidal NV occur in diseases of the outer retina and Bruch's membrane, the most prevalent of which is age-related macular degeneration. Numerous studies in mouse models have helped to elucidate the molecular pathogenesis underlying retinal, subretinal, and choroidal NV. There is considerable overlap because the precipitating event in each is stabilization of hypoxia inducible factor-1 (HIF-1) which leads to upregulation of several hypoxia-regulated gene products, including vascular endothelial growth factor (VEGF), angiopoietin 2, vascular endothelial-protein tyrosine phosphatase (VE-PTP), and several others. Stimulation of VEGF signaling and suppression of Tie2 by angiopoietin 2 and VE-PTP are critical for sprouting of retinal, subretinal, and choroidal NV, with perturbation of Bruch's membrane also needed for the latter. Additional HIF-1-regulated gene products cause further stimulation of the NV. It is difficult to model macular edema in animals and therefore proof-of-concept clinical trials were done and demonstrated that VEGF plays a central role and that suppression of Tie2 is also important. Neutralization of VEGF is currently the first line therapy for all of the above disease processes, but new treatments directed at some of the other molecular targets, particularly stabilization of Tie2, are likely to provide additional benefit for subretinal/choroidal NV and macular edema. In addition, the chronicity of these diseases as well as the implication of VEGF as a cause of retinal nonperfusion and progression of background diabetic retinopathy make sustained delivery approaches for VEGF antagonists a priority.
Ocular neovascularization Campochiaro, Peter A.
Journal of molecular medicine (Berlin, Germany),
03/2013, Letnik:
91, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Retinal and choroidal vascular diseases constitute the most common causes of moderate and severe vision loss in developed countries. They can be divided into retinal vascular diseases, in which there ...is leakage and/or neovascularization (NV) from retinal vessels, and subretinal NV, in which new vessels grow into the normally avascular outer retina and subretinal space. The first category of diseases includes diabetic retinopathy, retinal vein occlusions, and retinopathy of prematurity, and the second category includes neovascular age-related macular degeneration (AMD), ocular histoplasmosis, pathologic myopia, and other related diseases. Retinal hypoxia is a key feature of the first category of diseases resulting in elevated levels of hypoxia-inducible factor-1 (HIF-1) which stimulates expression of vascular endothelial growth factor (VEGF), platelet-derived growth factor-B (PDGF-B), placental growth factor, stromal-derived growth factor-1 and their receptors, as well as other hypoxia-regulated gene products such as angiopoietin-2. Although hypoxia has not been demonstrated as part of the second category of diseases, HIF-1 is elevated and thus the same group of hypoxia-regulated gene products plays a role. Clinical trials have shown that VEGF antagonists provide major benefits for patients with subretinal NV due to AMD and even greater benefits are seen by combining antagonists of VEGF and PDGF-B. It is likely that addition of antagonists of other agents listed above will be tested in the future. Other appealing strategies are to directly target HIF-1 or to use gene transfer to express endogenous or engineered anti-angiogenic proteins. While substantial progress has been made, the future looks even brighter for patients with retinal and choroidal vascular diseases.
Retinitis Pigmentosa (RP) is a group of diseases in which one of a large number of mutations causes death of rod photoreceptors. After rods die, cone photoreceptors slowly degenerate in a ...characteristic pattern. The mechanism of rod cell death varies depending upon the gene that is mutated and the rate that rods degenerate is an important prognostic feature, because cones do not begin to degenerate until almost all rods have been eliminated. Rod cell death causes night blindness, but visual disability and blindness result from cone degeneration and therefore it is critical to determine the mechanisms by which it occurs. The death of rods reduces oxygen consumption resulting in high tissue levels of oxygen in the outer retina. The excess oxygen stimulates superoxide radical production by mismatches in the electron transport chain in mitochondria and by stimulation of NADPH oxidase activity in cytoplasm. The high levels of superoxide radicals overwhelm the antioxidant defense system and generate more reactive species including peroxynitrite which is extremely damaging and difficult to detoxify. This results in progressive oxidative damage in cones which contributes to cone cell death and loss of function because drugs or gene transfer that reduce oxidative stress promote cone survival and maintenance of function. Compared with aqueous humor samples from control patients, those from patients with RP show significant elevation of carbonyl content on proteins indicating oxidative damage and a reduction in the ratio of reduced to oxidized glutathione indicating depletion of a major component of the antioxidant defense system from ongoing oxidative stress. The first step in clinical trials will be to identify doses of therapeutic agents that reverse these biomarkers of disease to assist in design of much longer trials with functional and anatomic endpoints.
•In Retinitis Pigmentosa (RP), rods die from a variety of mutations and then cones gradually die in a stereotypical pattern.•After rods die, oxygen levels in the outer retina is increased and there is progressive oxidative damage to cones.•Oxidative damage leads to cone cell death because antioxidants reduce oxidative damage and promote cone survival and function.•Compared to control patients, those with RP have increased carbonyl content and decrease ratio of reduced to oxidized glutathione.
Neovascular age-related macular degeneration (NVAMD) is the most prevalent choroidal vascular disease, and diabetic retinopathy (DR) and retinal vein occlusion (RVO) are the most prevalent retinal ...vascular diseases. In each of these, hypoxia plays a central role by stabilizing hypoxia-inducible factor-1 which increases production of vascular endothelial growth factor (VEGF) and other hypoxia-regulated gene products. High VEGF causes excessive vascular permeability, neovascularization, and in DR and RVO, promotes closure of retinal vessels exacerbating hypoxia and creating a positive feedback loop. Hence once VEGF expression is elevated it tends to remain elevated and drives disease progression. While other hypoxia-regulated gene products also contribute to pathology in these disease processes, it is remarkable how much pathology is reversed by selective inhibition of VEGF. Clinical trials have demonstrated outstanding visual outcomes in patients with NVAMD, DR, or RVO from frequent intraocular injections of VEGF-neutralizing proteins, but for a variety of reasons injection frequency has been substantially less in clinical practice and visual outcomes are disappointing. Herein we discuss the rationale, preclinical, and early clinical results of new approaches that provide sustained suppression of VEGF. These approaches will revolutionize the management of these prevalent retinal/choroidal vascular diseases.
•Persistent high VEGF expression drives retinal/choroidal vascular disease progression.•Attempts to minimize antiVEGF injections lead to poor outcomes.•Sustained suppression of VEGF is the best approach for these diseases.•Several strategies to achieve sustained VEGF suppression are in clinical trials.•These new strategies will revolutionize the management of these diseases.
To investigate baseline predictors of month 24 best-corrected visual acuity (BCVA) and central foveal thickness (CFT) in patients with diabetic macular edema (DME) treated monthly with ranibizumab or ...sham.
Post hoc analysis of DME patients in 2 identical phase 3 studies.
Patients randomized to ranibizumab (n = 502) or sham (n = 257).
Multivariate regression on predictors with P < 0.20 in univariate logistic regression using backward selection to retain predictors with P < 0.05.
Patient characteristics correlating with month 24 BCVA in Early Treatment Diabetic Retinopathy Study letter score ≥70 (20/40) or ≤50 (20/100), gain or loss from baseline BCVA of ≥15, or CFT ≤250 μm.
Baseline predictors of BCVA ≥20/40 in ranibizumab-treated patients were good BCVA, submacular fluid, no cardiovascular disease, no scatter photocoagulation, and male gender, whereas in sham-treated patients, they were mild increase in CFT, presence of hard exudates in center subfield, and absence of renal disease. Predictors of improvement in BCVA letter score ≥15 in ranibizumab-treated patients were poor BCVA, submacular fluid, young age, and short diabetes duration, and those in sham-treated patients were poor BCVA, young age, and mild increase in CFT. Predictors of resolution of edema (CFT ≤250 μm) in ranibizumab-treated patients were mild foveal thickening and prominent subfoveal fluid, and those in sham-treated patients were poor BCVA, mild foveal thickening, and statin usage. Month 24 BCVA ≤20/100 was predicted by poor baseline BCVA in ranibizumab-treated patients, and by poor baseline BCVA, large intraretinal cystoid spaces, renal disease, and absence of hypercholesterolemia in sham-treated patients. Loss of BCVA ≥15 letters was predicted in sham-treated patients by submacular fluid, intraretinal cystoid spaces, and renal disease.
Patients with DME and submacular fluid, intraretinal cysts, severe thickening, or renal disease respond poorly when untreated and respond well to ranibizumab treatment. Elimination of submacular fluid, intraretinal cysts, and severe thickening are important goals of DME treatment, and in patients with renal disease, treatment should be very aggressive, with a goal of eliminating all macular fluid.
Assess the 12-month efficacy and safety of intraocular injections of 0.3 mg or 0.5 mg ranibizumab in patients with macular edema after central retinal vein occlusion (CRVO).
Prospective, randomized, ...sham injection-controlled, double-masked, multicenter clinical trial.
We included 392 patients with macular edema after CRVO.
Eligible patients were randomized 1:1:1 to receive 6 monthly intraocular injections of 0.3 mg or 0.5 mg of ranibizumab or sham injections. After 6 months, all patients with BCVA ≤20/40 or central subfield thickness ≥250 μm could receive ranibizumab.
Mean change from baseline best-corrected visual acuity (BCVA) letter score at month 12, additional parameters of visual function, central foveal thickness (CFT), and other anatomic changes were assessed.
Mean (95% confidence interval) change from baseline BCVA letter score at month 12 was 13.9 (11.2-16.5) and 13.9 (11.5-16.4) in the 0.3 mg and 0.5 mg groups, respectively, and 7.3 (4.5-10.0) in the sham/0.5 mg group (P<0.001 for each ranibizumab group vs. sham/0.5 mg). The percentage of patients who gained ≥15 letters from baseline BCVA at month 12 was 47.0% and 50.8% in the 0.3 mg and 0.5 mg groups, respectively, and 33.1% in the sham/0.5 mg group. On average, there was a marked reduction in CFT after the first as-needed injection of 0.5 mg ranibizumab in the sham/0.5 mg group to the level of the ranibizumab groups, which was sustained through month 12. No new ocular or nonocular safety events were identified.
On average, treatment with ranibizumab as needed during months 6 through 11 maintained the visual and anatomic benefits achieved by 6 monthly ranibizumab injections in patients with macular edema after CRVO, with low rates of ocular and nonocular safety events. After sham injections for 6 months, treatment with ranibizumab as needed for 6 months resulted in rapid reduction in CFT in the sham/0.5 mg group to a level similar to that in the 2 ranibizumab treatment groups and an improvement in BCVA, but not to the same level as that in the 2 ranibizumab groups. Intraocular injections of ranibizumab provide an effective treatment for macular edema after CRVO.
Proprietary or commercial disclosure may be found after the references.
The demonstration that VEGF-A is a critical stimulus in retinal/choroidal vascular diseases and the development of intravitreous injections of potent VEGF-A antagonists as a therapy have greatly ...benefited millions of patients. However, compared with outcomes in clinical trials, those in clinical practice have been substantially worse because of difficulties maintaining sufficient frequency of injections. This unmet medical need has motivated development of a variety of new approaches to providing sustained suppression of VEGF. However, some clinicians and investigators are concerned that sustained suppression of VEGF may cause retinal damage and loss of vision. One reason for this concern is that conditional deletion of murine Vegfa in retinal pigmented epithelium or retina results in retinal damage. Transgenic expression of a potent VEGF-A- and -B--binding protein using the strong, retina-specific rhodopsin promoter for up to seven months caused no reduction in electroretinographic retinal function and no retinal damage in mice.
Assess 12-month efficacy and safety of intraocular injections of 0.3 mg or 0.5 mg ranibizumab in patients with macular edema after branch retinal vein occlusion (BRVO).
Prospective, randomized, sham ...injection-controlled, double-masked, multicenter trial.
A total of 397 patients with macular edema after BRVO.
Eligible patients were randomized 1:1:1 to 6 monthly injections of 0.3 mg or 0.5 mg ranibizumab or sham injections. After 6 months, all patients with study eye best-corrected visual acuity (BCVA) ≤20/40 or central subfield thickness ≥250 μm were to receive ranibizumab. Patients could receive rescue laser treatment once during the treatment period and once during the observation period if criteria were met.
The main efficacy outcome reported is mean change from baseline BCVA letter score at month 12. Additional visual and anatomic parameters were assessed.
Mean (95% confidence interval) change from baseline BCVA letter score at month 12 was 16.4 (14.5-18.4) and 18.3 (15.8-20.9) in the 0.3 mg and 0.5 mg groups, respectively, and 12.1 (9.6-14.6) in the sham/0.5 mg group (P<0.01, each ranibizumab group vs. sham/0.5 mg). The percentage of patients who gained ≥15 letters from baseline BCVA at month 12 was 56.0% and 60.3% in the 0.3 mg and 0.5 mg groups, respectively, and 43.9% in the sham/0.5 mg group. On average, there was a marked reduction in central foveal thickness (CFT) after the first as-needed injection of 0.5 mg ranibizumab in the sham/0.5 mg group, which was sustained through month 12. No new ocular or nonocular safety events were identified.
At month 12, treatment with ranibizumab as needed during months 6-11 maintained, on average, the benefits achieved by 6 monthly ranibizumab injections in patients with macular edema after BRVO, with low rates of ocular and nonocular safety events. In the sham/0.5 mg group, treatment with ranibizumab as needed for 6 months resulted in rapid reduction in CFT to a similar level as that in the 0.3 mg ranibizumab treatment group and an improvement in BCVA, but not to the extent of that in the 2 ranibizumab groups. Intraocular injections of ranibizumab provide an effective treatment for macular edema after BRVO.
Proprietary or commercial disclosure may be found after the references.
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