Effects of Aflibercept for Neovascular Age-Related Macular Degeneration: A Systematic Review and Meta-Analysis of Observational Comparative Studies

Comparison of Efficacy and Safety between Conbercept and Ranibizumab in Neovascular Age-Related Macular Degeneration: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Conbercept, as a novel vascular endothelial growth factor (VEGF) inhibitor, was approved for the treatment of neovascular age-related macular degeneration (nAMD) in China.

OBJECTIVE

This study aimed to compare the efficacy and safety between conbercept and ranibizumab in patients with nAMD.

METHODS

Several databases (PubMed, Web of Science, China National Knowledge Infrastructure, and WANFANG) were searched for the results of studies describing conbercept and ranibizumab for the treatment of nAMD. Sixteen randomized controlled trials including 1,224 eyes met our search criteria and were assessed.

RESULTS

Conbercept and ranibizumab had comparable effects on improving visual acuity at 3 months (standardized mean difference [SMD]: -0.19; 95% confidence interval [CI]: -0.46 to 0.08; p = 0.17) and 6-12 months (SMD: -0.01; 95% CI: -0.20 to 0.18; p = 0.90). At 3 months and 6-12 months, the differences in the change of central macular thickness in conbercept and ranibizumab groups were 1.06 μm (95% CI: -3.52 to 5.64; p = 0.65) and -0.12 μm (95% CI: -9.26 to 9.02; p = 0.98). In the short term, there was no significant difference between the 2 groups with respect to ocular adverse events (odds ratio [OR]: 0.86; 95% CI: 0.46-1.61; p = 0.63). No significant differences were observed in the recovery rate of choroidal neovascularization leakage between conbercept and ranibizumab at both 3 months (OR: 1.49; 95% CI: 0.83-2.68; p = 0.18) and 6-12 months (OR: 0.66; 95% CI: 0.18-2.43; p = 0.53). There were significant differences between conbercept and ranibizumab in terms of decreasing intraocular pressure (weighted mean difference [WMD]: -1.74; 95% CI: -2.28 to -1.20; p < 0.00001), the plasma VEGF level (WMD: -21.49; 95% CI: -26.28 to -16.70; p < 0.00001), and the C-reactive protein level (WMD: -1.16; 95% CI: -1.45 to -0.87; p < 0.00001) in the short term.

CONCLUSION

Conbercept was similar to ranibizumab in terms of efficacy and safety for the treatment of nAMD in China. Further studies with longer term observation are needed to support this conclusion.

VEGFR1 signaling in retinal angiogenesis and microinflammation

Five vascular endothelial growth factor receptor (VEGFR) ligands (VEGF-A, -B, -C, -D, and placental growth factor [PlGF]) constitute the VEGF family. VEGF-A binds VEGF receptors 1 and 2 (VEGFR1/2), whereas VEGF-B and PlGF only bind VEGFR1. Although much research has been conducted on VEGFR2 to elucidate its key role in retinal diseases, recent efforts have shown the importance and involvement of VEGFR1 and its family of ligands in angiogenesis, vascular permeability, and microinflammatory cascades within the retina. Expression of VEGFR1 depends on the microenvironment, is differentially regulated under hypoxic and inflammatory conditions, and it has been detected in retinal and choroidal endothelial cells, pericytes, retinal and choroidal mononuclear phagocytes (including microglia), Müller cells, photoreceptor cells, and the retinal pigment epithelium. Whilst the VEGF-A decoy function of VEGFR1 is well established, consequences of its direct signaling are less clear. VEGFR1 activation can affect vascular permeability and induce macrophage and microglia production of proinflammatory and proangiogenic mediators. However the ability of the VEGFR1 ligands (VEGF-A, PlGF, and VEGF-B) to compete against each other for receptor binding and to heterodimerize complicates our understanding of the relative contribution of VEGFR1 signaling alone toward the pathologic processes seen in diabetic retinopathy, retinal vascular occlusions, retinopathy of prematurity, and age-related macular degeneration. Clinically, anti-VEGF drugs have proven transformational in these pathologies and their impact on modulation of VEGFR1 signaling is still an opportunity-rich field for further research.

Prospective Clinical Trial of Intravitreal Aflibercept Treat-and-extend Regimen for Diabetic Macular Edema: 1-Year Outcomes

Purpose

To investigate the efficacy of aflibercept for the treatment of diabetic macular edema via a treat-and-extend regimen.

Methods

This prospective, single-center, open-label, interventional study involved 30 patients with a best-corrected visual acuity (BCVA) ≤0.6 and a central retinal thickness (CRT) ≥300 µm. The enrolled eyes each received a monthly intravitreal aflibercept injection until the CRT decreased below 300 µm, upon which the administration interval was extended for 1 month until the CRT once again increased to ≥300 µm. Main outcome measures were median BCVA and CRT at 6 and 12 months after initiation of treatment via last observation carried forward analysis, the median number of injections over the 12 months, and the effects on the diabetic retinopathy severity scale (DRSS) score of the patients who completed the 12-month follow-up period.

Results

Of the 30 enrolled patients, 29 and 25 respectively completed the 6- and 12-month follow-up examinations. From baseline to 6 and 12 months after treatment initiation, the median BCVA (logarithm of the minimum angle of resolution) significantly improved from 0.52 to 0.30 and 0.35, respectively, and the median CRT significantly decreased from 439.5 to 268.5 and 249.0 µm, respectively. The median number of injections over the 12-month follow-up period was 6.0. Compared to baseline, the DRSS score at 12 months was improved by 2 steps in 16% of patients; in no cases did the DRSS score worsen or improve by three steps or more.

Conclusions

When administered in a treat-and-extend regimen, aflibercept is an effective treatment option for diabetic macular edema.

2-Year Real-World Outcomes with Intravitreal Aflibercept in Neovascular Age-Related Macular Degeneration: Literature Review and Meta-analysis of Patient-Relevant Outcomes

BACKGROUND

The 96 weeks' assessment from the VIEW studies provided insights into the long-term efficacy of intravitreal aflibercept (IVT-AFL) in neovascular age-related macular degeneration (nAMD) and demonstrated that it was possible to maintain long-term outcomes while moving from a fixed bimonthly regimen in Year 1 to a variable dosing regimen in Year 2. The aim of this analysis was to perform a literature review and meta-analysis assessing the use of IVT-AFL and real-world outcomes in treatment-naïve patients with nAMD treated with IVT-AFL for 2 years, as per label.

METHODS

A literature review and meta-analysis were performed to provide an overview of the baseline characteristics of the population, the 2-year outcomes, the associated treatment burden, and safety.

RESULTS

Eleven publications providing data from patients with nAMD who had treatment initiated with IVT-AFL between 2012 and 2016 were identified. The mean baseline age of patients was 78.62 years, with a baseline best-corrected visual acuity (BCVA) of 57.73 Early Treatment Diabetic Retinopathy Study (ETDRS) letters. Patients reported a mean BCVA at 2 years of 62.55 ETDRS letters, with 47.39% of patients having a BCVA ≥ 70 ETDRS letters. Mean gain in BCVA versus baseline was + 4.49 ETDRS letters for the combined population (+ 5.91 letters for patients treated with a treat-and-extend regimen). Over the 2 years of the study, patients received an average of 12.34 injections, with a reduction in injections in Year 2 versus Year 1. The qualitative assessment of the safety data suggested that no new safety signals were identified.

CONCLUSION

Patients treated with IVT-AFL reported significant gains in visual acuity versus baseline after 2 years. The evidence identified indicates that the visual gains achieved during the first year of treatment are maintained through the second year and that these were achieved with a reduction in the mean number of IVT-AFL injections administered in Year 2 of treatment.

Evaluation of Blood Coagulation Parameters and ADMA, NO, IL-6, and IL-18 Serum Levels in Patients with Neovascular AMD before, during, and after the Initial Loading Phase of Intravitreal Aflibercept

We evaluated the effect of intravitreal injections of aflibercept (IVA) on blood coagulation parameters including prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT), as well as asymmetric dimethylarginine (ADMA), nitric oxide (NO), interleukin 6 (IL-6), and interleukin 18 (IL-18) serum levels in patients with neovascular AMD (nAMD). Twenty-two eyes of 22 patients with nAMD were included. Parameters were evaluated before and 2–3 days after the first IVA injection, and then immediately before and 2–3 days after the third IVA injection. We revealed prolongation of the TT after the initial loading phase of IVA (p = 0.041) and a significant increase in IL-18 serum concentration immediately before the third IVA administration compared to baseline (p = 0.037). There were no statistically significant differences of other parameters and PT, APTT, ADMA, NO, and IL-6 values remained within the normal range at each of the time points of the study. Our results suggest that repeated IVA administration may affect the common blood coagulation pathway, which manifests as a prolongation of the TT value. Furthermore, we showed a significant increase in serum concentration of the pro-inflammatory cytokineIL-18during the initial loading phase of IVA.

Soluble ligands as drug targets

Historically, the main classes of drug targets have been receptors, enzymes, ion channels and transporters. However, owing largely to the rise of antibody-based therapies in the past two decades, soluble protein ligands such as inflammatory cytokines have become an increasingly important class of drug targets. In this Review, we analyse drugs targeting ligands that have reached clinical development at some point since 1992. We identify 291 drugs that target 99 unique ligands, and we discuss trends in the characteristics of the ligands, drugs and indications for which they have been tested. In the last 5 years, the number of ligand-targeting drugs approved by the FDA has doubled to 34, while the number of clinically validated ligand targets has doubled to 22. Cytokines and growth factors are the predominant types of targeted ligands (70%), and inflammation and autoimmune disorders, cancer and ophthalmological diseases are the top therapeutic areas for both approved agents and agents in clinical studies, reflecting the central role of cytokine and/or growth factor pathways in such diseases.

Cost-minimization Analysis of Ranibizumab versus Aflibercept in the Treatment of Neovascular Age-related Macular Degeneration in Colombia

BACKGROUND

In 2020 Colombia may expect to have close to 231,700 patients with neovascular age-related macular degeneration (ARMD). Treatment of neovascular ARMD involves the sequential Intra-vitreal injections of anti-vascular endothelial growth factor (anti-VEGF therapy) medications. The efficacy and safety of anti-VEGF therapy on a treat-and-extend (T&E) dosing scheme are similar when ranibizumab or aflibercept are administered. Objective : A cost-minimization analysis from the payer`s perspective in Colombia projects treatment expenses of anti-VEGF therapy using aflibercept or ranibizumab on T&E regimens for the treatment of neovascular ARMD. Methods : A model projects the expenses of the compared treatment regimens for two and five-year periods beginning on February 2020. The model used information from clinical trials, case series and meta-analyses on the compared treatment regimens, demographic, epidemiologic and economic data originated from the Colombian government sources. A 3% discount rate was applied. Results : Projected cost differences in favor of ranibizumab after two and five-year treatment periods beginning February 2020 could be close to U.S. $ 4,861 and U.S $ 7,241 per treated eye, respectively. If all patients with unilateral and bilateral neovascular ARMD in Colombia were to receive appropriate anti-VEGF therapy for two years, the projected expected cost difference in favor of ranibizumab could be close to U.S. $ 462,717,092 dollars. Conclusion : Within the Colombian healthcare setting anti-VEGF therapy on a T&E regimen utilizing ranibizumab for neovascular ARMD may be cost-saving compared with employing aflibercept. Despite cost favorability, ranibizumab should not be the only therapeutic option since in clinical practice alternatives are required.

Short-term effect on the ocular circulation induced by unilateral intravitreal injection of aflibercept in age-related maculopathy

Purpose

Intravitreal injection of anti‐vascular endothelial growth factor (anti‐VEGF) is the standard treatment for neovascular age‐related macular degeneration (AMD). As VEGF is a physiological key player for regulating retinal vascular tone, questions have been raised whether the application of anti‐VEGF could induce alterations in ocular perfusion.

Methods

The study included 20 eyes from 20 Caucasian patients with unilateral neovascular AMD and 20 fellow eyes. All eyes were treated with standard intravitreal injection of aflibercept (IVA). Measurements of blood flow at the optic nerve head (ONH) and the choroid were performed with laser speckle flowgraphy (LSFG). The intraocular pressure (IOP), systolic and diastolic blood pressure, heart rate, mean arterial pressure (MAP) and ocular perfusion pressure (OPP) were analysed. Measurements were performed at baseline and repeated immediately after the injection and 30 and 45 min later.

Results

Mean time between injection of aflibercept and first follow‐up was 8:56 ± 4:25 min. The injection led to significant rise in IOP. In the injected eyes, mean blur rate (MBR, i.e. a relative measure of perfusion and the main outcome parameter of LSFG) within the major vessels of the ONH as well as at the entire ONH region decreased significantly (p < 0.001). No change in MBR was observed in the fellow eye. Choroidal blood flow was maintained stable in both eyes.

Conclusion

Intravitreal injection of aflibercept (IVA) led to a short‐term reduction in perfusion only in the treated eye. This was independent from IOP, indicating a direct pharmacological effect. No changes in choroidal perfusion were observed during the first 45 min after the injection.

The Placental Growth Factor Pathway and Its Potential Role in Macular Degenerative Disease

There is growing evidence that placental growth factor (PlGF) is an important player in multiple pathologies, including tumorigenesis, inflammatory disorders and degenerative retinopathies. PlGF is a member of the vascular endothelial growth factor (VEGF) family and in the retina, binding of this growth factor to specific receptors is associated with pathological angiogenesis, vascular leakage, neurodegeneration and inflammation. Although they share some receptor signalling pathways, many of the actions of PlGF are distinct from VEGF and this has revealed the enticing prospect that it could be a useful therapeutic target for treating early and late stages of diabetic retinopathy (DR) and neovascular age-related macular degeneration (AMD). Recent research suggests that modulation of PlGF could also be important in the geographic atrophy (GA) form of late AMD by protecting the outer retina and the retinal pigment epithelium (RPE). This review discusses PlGF and its signalling pathways and highlights the potential of blocking the bioactivity of this growth factor to treat irreversible visual loss due to the two main forms of AMD.

A Mathematical Analysis of Aerobic Glycolysis Triggered by Glucose Uptake in Cones

Patients affected by retinitis pigmentosa, an inherited retinal disease, experience a decline in vision due to photoreceptor degeneration leading to irreversible blindness. Rod-derived cone viability factor (RdCVF) is the most promising mutation-independent treatment today. To identify pathologic processes leading to secondary cone photoreceptor dysfunction triggering central vision loss of these patients, we model the stimulation by RdCVF of glucose uptake in cones and glucose metabolism by aerobic glycolysis. We develop a nonlinear system of enzymatic functions and differential equations to mathematically model molecular and cellular interactions in a cone. We use uncertainty and sensitivity analysis to identify processes that have the largest effect on the system and their timeframes. We consider the case of a healthy cone, a cone with low levels of glucose, and a cone with low and no RdCVF. The three key processes identified are metabolism of fructose-1,6-bisphosphate, production of glycerol-3-phosphate and competition that rods exert on cone resources. The first two processes are proportional to the partition of the carbon flux between glycolysis and the pentose phosphate pathway or the Kennedy pathway, respectively. The last process is the rods' competition for glucose, which may explain why rods also provide the RdCVF signal to compensate.

Co-inhibition of PGF and VEGF blocks their expression in mononuclear phagocytes and limits neovascularization and leakage in the murine retina

Background

Age-related macular degeneration (AMD) is a leading cause of visual impairment in the elderly. The neovascular (wet) form of AMD can be treated with intravitreal injections of different anti-vascular endothelial growth factor (VEGF) agents. Placental growth factor (PGF) is another member of the VEGF family of cytokines with pro-angiogenic and pro-inflammatory effects. Here, we aimed to compare single and combined inhibition of VEGF-A and PGF in the laser-induced mouse model of choroidal neovascularization (CNV) with a focus on the effects on retinal mononuclear phagocytes.

Methods

CNV was induced in C57BL/6J mice using a YAG-Laser. Immediately after laser damage antibodies against VEGF-A (aVEGF), anti-PGF (aPGF), aVEGF combined with aPGF, aflibercept, or IgG control were injected intravitreally in both eyes. Three and 7 days after laser damage, the vascular leakage was determined by fluorescence angiography. Lectin staining of retinal and RPE/choroidal flat mounts was used to monitor CNV. In situ mRNA co-expression of Iba1, VEGF and PGF were quantified using in situ hybridization. Retinal and RPE/choroidal protein levels of VEGF and PGF as well as the pro-inflammatory cytokines IL-6, IL1-beta, and TNF were determined by ELISA.

Results

Early (day 3) and intermediate (day 7) vascular leakage and CNV were significantly inhibited by PGF and VEGF-A co-inhibition, most effectively with the trap molecule aflibercept. While VEGF-A blockage alone had no effects, trapping PGF especially with aflibercept prevented the accumulation of reactive microglia and macrophages in laser lesions. The lesion-related mRNA expression and secretion of VEGF-A and PGF by mononuclear phagocytes were potently suppressed by PGF and partially by VEGF-A inhibition. Protein levels of IL-6 and IL1-beta were strongly reduced in all treatment groups.

Conclusions

Retinal inhibition of PGF in combination with VEGF-A prevents vascular leakage and CNV possibly via modulating their own expression in mononuclear phagocytes. PGF-related, optimized strategies to target inflammation-mediated angiogenesis may help to increase efficacy and reduce non-responders in the treatment of wet AMD patients.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1419-2) contains supplementary material, which is available to authorized users.

Analysis of genetic polymorphisms for age-related macular degeneration (AMD) in Chinese Tujia ethnic minority group

Background

Age-related macular degeneration (AMD) can cause vision loss or blindness in elderly. The associations between single nucleotide polymorphism (SNP) and AMD in Chinese Tujia ethnic minority group are still unclear.

Methods

A total of 2122 Tujia volunteers were recruited and 197 of them were diagnosed with AMD (either dry or wet type).Then the blood specimens of these 197 AMD patients and 404 controls from the remaining 1925 normal Tujia volunteers were collected to detect the frequencies of 39 chosen SNPs. The Bonferroni method was used to correct the P values from the Fisher’s exact test.

Results

The mean age of the 197 AMD patients(113 males and 84 females) was 68.4197 years old. No significant differences in allelic and genotypic frequencies were found for all the 39 SNPs between the patients and controls. However, weak correlations between 10 SNPs (CFH rs1329428 TT genotype, CFH rs3753394 CC genotype and T allele, CFH rs1410996 AA genotype, CFH rs800292 AA genotype, CFH rs800292 A allele, VEGF rs833061 TT genotype and C allele, VEGF rs2010963 CG genotype, VEGFR2 rs1531289 TT genotype, ARMS2 rs10490924 TT genotype, KCTD10 rs238104 GC genotype, rs1531289 T allele and ARMS2 rs10490924 T allele) and AMD were shown.

Conclusions

The effects of 39 SNPs have found no associations with the morbidity of AMD in Chinese Tujia ethnic minority group.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0756-4) contains supplementary material, which is available to authorized users.

Mechanisms Underlying the Visual Benefit of Cell Transplantation for the Treatment of Retinal Degenerations

The transplantation of retinal cells has been studied in animals to establish proof of its potential benefit for the treatment of blinding diseases. Photoreceptor precursors have been grafted in animal models of Mendelian-inherited retinal degenerations, and retinal pigmented epithelial cells have been used to restore visual function in animal models of age-related macular degeneration (AMD) and recently in patients. Cell therapy over corrective gene therapy in inherited retinal degeneration can overcome the genetic heterogeneity by providing one treatment for all genetic forms of the diseases. In AMD, the existence of multiple risk alleles precludes a priori the use of corrective gene therapy. Mechanistically, the experiments of photoreceptor precursor transplantation reveal the importance of cytoplasmic material exchange between the grafted cells and the host cells for functional rescue, an unsuspected mechanism and novel concept. For transplantation of retinal pigmented epithelial cells, the mechanisms behind the therapeutic benefit are only partially understood, and clinical trials are ongoing. The fascinating studies that describe the development of methodologies to produce cells to be grafted and demonstrate the functional benefit for vision are reviewed.

Treat-and-extend therapy using intravitreal aflibercept for neovascular age-related macular degeneration: 2-year real-world practice data from Slovenia

Background

To assess visual outcomes over 24 months in patients with neovascular age-related macular degeneration (nAMD) who initiated intravitreal aflibercept therapy under a treat-and-extend (TE) regimen in real-world settings.

Methods

In this retrospective, observational, multicentre study in Slovenia, medical records of all treatment-naïve patients with nAMD who started intravitreal aflibercept therapy between October 2013 and April 2015 were reviewed. The primary outcome measure was change in mean visual acuity (VA) from baseline to 24 months in patients who received the TE regimen for 2 years, assessed by standardised Early Treatment Diabetic Retinopathy Study charts and calculated as least-squares means. Other outcome measures included the numbers of injections and visits at 12 months and 24 months.

Results

The primary analysis included 115 eyes of 105 patients who received TE treatment for 2 years (Group A). The mean VA improved from 57.9 ± 14.9 letters at baseline to 64.6 ± 15.8 letters (+ 6.5 letters, p < 0.0001) at 12 months and 64.8 ± 15.6 letters (+ 7.0 letters, p < 0.0001) at 24 months. The mean number of injections per eye was 8.4 ± 1.9 and the mean number of visits was 8.8 ± 1.7 at 12 months; these numbers decreased to 6.1 ± 2.0 and 6.4 ± 1.9, respectively, at 24 months. The additional analysis included 33 eyes of 33 patients who received TE treatment in Year 1, followed by pro re nata treatment in Year 2 (Group B). Compared with Group A whose vision improvement was maintained at 24 months, the VA gain in Group B eyes seen at 12 months (change in mean VA vs baseline: + 6.9 letters, p = 0.0008) was no longer present at 24 months (change in mean VA vs baseline: + 1.2 letters, p = 0.5733).

Conclusions

Using the TE regimen in clinical practice, intravitreal aflibercept significantly improved visual outcomes in treatment-naïve patients with nAMD, which were maintained over time. TE therapy with intravitreal aflibercept is a rational long-term strategy that can produce favourable outcomes in clinical practice.

Real-World Results of Aflibercept versus Ranibizumab for the Treatment of Exudative AMD Using a Fixed Regimen

Intravitreal injections of antivascular endothelial growth factors have been considered a milestone in the treatment of neovascular age-related macular degeneration (nAMD). However, the increasing incidence of AMD and the burden of visits and injections overcharge both the patient and the healthcare systems. Real-world solutions depend on treatment protocols aimed at optimizing the number of clinical visits while guaranteeing good functional outcomes. We performed a retrospective analysis of 72 eyes from 63 naïve patients diagnosed with nAMD that underwent a fixed intravitreal protocol consisting of bimonthly injections after a three-month loading dose, with either Aflibercept or Ranibizumab (no predefined criteria for treatment selection). Best corrected visual acuity (BCVA) and optical coherence tomography were analyzed at baseline and during follow-up clinical visits (months 3, 6, 12, and 18). From the included participants, 42 followed a fixed regimen with Aflibercept and 30 with Ranibizumab. At the 12-month visit, there was not a statistically significant difference in the mean change of BCVA between the two groups (p=0.121); however, the mean difference in the central retinal thickness was significantly superior in the Aflibercept group (-142.2 versus -51.5, p=0.011). The described fixed regimen seems to be efficient in the treatment of nAMD in a clinical practice setting.