Comparison of subconjunctivally injected bevacizumab, ranibizumab, and pegaptanib for inhibition of corneal neovascularization in a rat model

Intrastromal versus subconjunctival anti-VEGF agents for treatment of corneal neovascularization: a rabbit study

OBJECTIVE

To determine whether subconjunctival or intrastromal administration of anti-VEGF agents is more effective on suture-induced corneal neovascularization (CoNV) in rabbits.

METHODS

CoNV was induced in 48 eyes of 24 New Zealand white rabbits by using an 8/0 silk suture. On the 7th day after suturing, the rabbits were divided into four treatment groups as follows: six rabbits received subconjunctival bevacizumab (group 1), six rabbits received subconjunctival aflibercept (group 2), six rabbits received intrastromal bevacizumab (group 3) and six rabbits received intrastromal aflibercept (group 4). On the 7th and 14th days after suturing, the CoNV area was calculated by standardised analysis of photographs using the Image-J program. On the 14th day after suturing, all rabbits were sacrificed and then corneal tissue was harvested for the analysis of vascular endothelial growth factor (VEGF)-A, VEGF-B and placental growth factor (PIGF) levels.

RESULTS

On the 7th day after suturing, CoNV areas were 17.10 ± 2.98, 18.88 ± 3.78, 17.36 ± 4.52, 18.57 ± 4.16 and 17.31 ± 2.81 mm² in the groups 1-4 and control group, respectively. On the 7th day after intervention and removal of suture, CoNV areas were 4.85 ± 1.99, 6.66 ± 1.73, 2.83 ± 1.08, 2.63 ± 1.16 and 11.93 ± 2.64 mm² in the group 1-4 and control group, respectively. CoNV area was reduced by 88.1% and 82.5% in eyes receiving intrastromal aflibercept and bevacizumab, respectively (both p < 0.001), and by 64.5% and 69.9% in eyes receiving subconjunctival aflibercept and bevacizumab, respectively (both p = 0.001).

CONCLUSION

Intrastromal anti-VEGF therapy regressed CoNV more effectively than subconjunctival therapy regardless of the type of anti-VEGF agent.

Comparing The Efficacy Of An Anti-Human VEGF-A Neutralizing Antibody Versus Bevacizumab On A Laser-Induced Choroidal Neovascularization (CNV) Rhesus Monkey Model

Purpose

To evaluate the efficacy of a therapy on improving characteristics of laser-induced choroidal neovascularization (CNV) via single intravitreal injection of a humanized anti-human VEGF monoclonal antibody (PRO-169) versus bevacizumab in a rhesus monkey model.

Methods

To induce experimental CNV, small high-energy laser spots were used to treat several areas, around the macula in the retinas of monkeys at Day −21. Eighteen rhesus monkeys were used for CNV induction. The efficacy endpoints were fluorescein leakage by FFA and retinal thickness by OCT. FFA examinations were performed 19 days after induction. Appropriate animals were enrolled for treatment and randomly divided into 3 groups: bevacizumab (n=5, 7 eyes), PRO-169 (n=5, 7 eyes), and vehicle controls (n=4, 7 eyes).

Results

In 25 of 36 (69.4%) eyes, CNV lesions were identified. The average percent change of retinal thickness in the eyes of bevacizumab group was −159.3±62.2% and −154.0±45.1% (p<0.01 vs Vehicle) at Day 14 and Day 28, respectively; in the eyes of PRO-169 group it was −131.6±68.7% and −131.5±63.8% (p<0.01 vs Vehicle), respectively. The average percent change of leakage area in the eyes of bevacizumab group was −75.3±49.4% and −78.0±42.6% (p<0.01 vs Vehicle) at Day 14 and Day 28, respectively; in the eyes of PRO-169 group it was −82.0±19.3% and −81.4±21.0% (p<0.01 vs Vehicle), respectively. There were no abnormalities found in behavior, skin and hair, excretion and overall eye appearance before and after treatment in all groups.

Conclusion

After photocoagulation, the eyes enrolled in this studio showed CNV related characteristics including increased retinal thickness, and fluorescein leakage at laser spots. PRO-169 (1.25 mg per eye) can reduce the retinal thickness and fluorescein leakage area after treatment for 14 and 28 days in this rhesus monkeys model, without toxic effect or adverse events. These findings suggested that PRO-169 can inhibit CNV.

Current and emerging therapies for corneal neovascularization

The cornea is unique because of its complete avascularity. Corneal neovascularization (CNV) can result from a variety of etiologies including contact lens wear; corneal infections; and ocular surface diseases due to inflammation, chemical injury, and limbal stem cell deficiency. Management is focused primarily on the etiology and pathophysiology causing the CNV and involves medical and surgical options. Because inflammation is a key factor in the pathophysiology of CNV, corticosteroids and other anti-inflammatory medications remain the mainstay of treatment. Anti-VEGF therapies are gaining popularity to prevent CNV in a number of etiologies. Surgical options including vessel occlusion and ocular surface reconstruction are other options depending on etiology and response to medical therapy. Future therapies should provide more effective treatment options for the management of CNV.

Comparison of the Effects of Subconjunctival Injections of Bevacizumab and Interferon Alpha-2a on Corneal Angiogenesis in a Rat Model

Background and objective: Corneal neovascularization (CNV) is a vision-threatening condition arising from various corneal diseases. The aim of this study is to compare the effectiveness of bevacizumab and interferon alpha-2a (IFNα-2a) treatment on corneal neovascularization. Materials and Methods: Twenty-four Wistar albino rats were used in this study. After cauterization of the cornea with a silver nitrate applicator stick, the control group received 0.1 mL saline solution, the second group received 0.1 mL IFNα-2a (IFNα-2a, 6 million international units [MIU]/0.5 mL), and the third group received 2.5 mg bevacizumab by subconjunctival injection. An additional injection was administered to each group on the fourth day. After one week, the corneal neovascularization rate and the longest neovascular sprout length were determined. Results: The neovascularization rate (saline 0.65 ± 0.05; IFNα-2a 0.62 ± 0.07; bevacizumab 0.42 ± 0.11) with bevacizumab was significantly lower, more than those with IFNα-2a and saline (p < 0.001 and p < 0.001). The longest neovascular sprout length (saline, 4.00 ± 0.6 mm; IFNα-2a, 3.63 ± 0.52 mm; bevacizumab, 2.81 ± 0.65 mm) with bevacizumab was significantly shorter than those with saline and IFNα-2a (p = 0.001 and p = 0.012). Conclusions: Subconjunctival IFNα-2a has limited efficacy in the treatment of corneal neovascularization.

Transcriptome Profiling of Neovascularized Corneas Reveals miR-204 as a Multi-target Biotherapy Deliverable by rAAVs

Corneal neovascularization (NV) is the major sight-threatening pathology caused by angiogenic stimuli. Current drugs that directly target pro-angiogenic factors to inhibit or reverse the disease require multiple rounds of administration and have limited efficacies. Here, we identify potential anti-angiogenic corneal microRNAs (miRNAs) and demonstrate a framework that employs discovered miRNAs as biotherapies deliverable by recombinant adeno-associated viruses (rAAVs). By querying differentially expressed miRNAs in neovascularized mouse corneas induced by alkali burn, we have revealed 39 miRNAs that are predicted to target more than 5,500 differentially expressed corneal mRNAs. Among these, we selected miR-204 and assessed its efficacy and therapeutic benefit for treating injured corneas. Our results show that delivery of miR-204 by rAAV normalizes multiple novel target genes and biological pathways to attenuate vascularization of injured mouse cornea. Importantly, this gene therapy treatment alternative is efficacious and safe for mitigating corneal NV. Overall, our work demonstrates the discovery of potential therapeutic miRNAs in corneal disorders and their translation into viable treatment alternatives.

Therapeutic approaches for corneal neovascularization

Angiogenesis refers to new blood vessels that originate from pre-existing vascular structures. Corneal neovascularization which can lead to compromised visual acuity occurs in a wide variety of corneal pathologies. A large subset of measures has been advocated to prevent and/or treat corneal neovascularization with varying degrees of success. These approaches include topical corticosteroid administration, laser treatment, cautery, and fine needle diathermy. Since the imbalance between proangiogenic agents and antiangiogenic agents primarily mediate the process of corneal neovascularization, recent therapies are intended to disrupt the different steps in the synthesis and actions of proangiogenic factors. These approaches, however, are only partially effective and may lead to several side effects. The aim of this article is to review the most relevant treatments for corneal neovascularization available so far.

Topical Timolol Inhibits Corneal Neovascularization in Rabbits

Timolol is a non-selective beta-adrenergic antagonist that is similar to propranolol. The mechanism through which these drugs act on the regression of neovascularization is largely unknown. However, it is thought that the drugs may act through vascular endothelial growth factor signaling, vasoconstriction, and vascular endothelial cell apoptosis. The aim of this study was to determine the effect of timolol on corneal neovascularization in rabbits. Neovascularization was induced in the eyes of 20 rabbits. Next, the rabbits were divided into two groups: the timolol (experimental) group received eye drops containing timolol 0.5% twice per day; and the saline (control) group received saline drops twice per day for two weeks. After 7 days, the mean area of corneal neovascularization (presented as a percentage relative to baseline) was significantly lower in the timolol group than in the saline group (4.63 ± 4.61% versus 58.39 ± 6.31%, P < 0.001). After 2 weeks, the mean area of corneal neovascularization was 0.85 ± 1.33% in the timolol group and 1.73 ± 2.06% in the saline group (P = 0.315). After the first week of treatment, timolol significantly reduced the area of neovascularization compared to control. Timolol may increase the rate of recovery from corneal neovascularization.

Corneal neovascularization and biological therapy

Corneal avascularity is necessary for the preservation of optimal vision. The cornea maintains a dynamic balance between pro- and antiangiogenic factors that allows it to remain avascular under normal homeostatic conditions. Corneal neovascularization (NV) is a condition that can develop in response to inflammation, hypoxia, trauma, or limbal stem cell deficiency and it is a significant cause of blindness. New therapeutic options for diseases of the cornea and ocular surface are now being explored in experimental animals and clinical trials. Antibody based biologics are being tested for their ability to reduce blood and lymphatic vessel ingrowth into the cornea, and to reduce inflammation. Numerous studies have shown that biologics with specificity for VEGF A such as bevacizumab and ranibizumab (a recombinant antibody and an antibody fragment, respectively) or anti-tumor necrosis factor-α microantibody, are effective in the treatment of corneal neovascularization.