As a popular target for treating diseases like macular degeneration and tumors, vascular endothelial growth factor (VEGF) has already had several drugs approved for clinical use and has made significant progress. In February of this year, researchers completed the first Phase I clinical trial of a recombinant anti-VEGFA and VEGFC bispecific antibody fusion protein in a for age-related macular degeneration with neovascularization. In the field of tumors, there have also been new developments. Clinical studies for a new PD-1/VEGF bispecific antibody drug called AK112 are being conducted to evaluate its potential targeting of relevant solid tumors and enhancement of antitumor activity, including a Phase II clinical trial for advanced gastrointestinal tumors and a Phase III trial for combination with docetaxel for Non-Small-Cell Lung Carcinoma (NSCLC) patients.

VEGF includes various types such as VEGFA, VEGFB, VEGFC, VEGFD, VEGFE, and PLGF. In current ophthalmic drug research, VEGFA is the most common and is the main stimulant factor leading to neovascularization. In our previous topic, "Ophthalmic Gene Therapy,'' we discussed the research progress related to VEGFA and the development of preclinical animal models. You can review it by clicking here. Today, we will focus on discussing the development of anti-VEGF drugs.

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1. The relationship between VEGF and Ophthalmic Diseases

Due to the strong correlation between VEGF in the eye and the development of choroidal neovascularization (CNV), VEGF is considered as a promising treatment target for choroidal and retinal neovascularization. Currently, it is widely used in the research and treatment of wet age-related macular degeneration (wAMD).

Anti-VEGF drugs have been effective in reducing neovascularization and edema, greatly improving the prognosis of patients with wAMD. In clinical practice, intravitreal injection is commonly used to administer anti-VEGF drugs to treat wAMD. It can be said that drugs targeting VEGF have provided a new path for the treatment of ocular neovascular diseases.

2. The clinical application of anti-VEGF drugs in ophthalmology

As VEGF is a key mediator in the development of CNV, drugs that inhibit or neutralize VEGF expression have become a main choice for the clinical treatment of wAMD over the past decade. Examples of such drugs include Aflibercept, Conbercept, Bevacizumab, and Ranibizumab.

Aflibercept is a soluble VEGF decoy receptor that has higher affinity for all subtypes of VEGF compared to drugs like Ranibizumab. It works by inhibiting the activity of VEGF, thereby preventing the growth of new blood vessels and reducing fluid leakage and retinal tissue edema. In 2011, It was approved by the US FDA for the treatment of exudative age-related macular degeneration.

As a new type of anti-VEGF drug, Aflibercept has the advantages of long half-life and short dosing intervals. However, there is far less research on it compared to drugs like Bevacizumab and Ranibizumab, and there is still a lot of room for exploration in its clinical application.

Using Cyagen’s self-developed humanized-VEGF (hVEGF) mouse model, Cyagen conducted positive drug tests such as Aflibercept to evaluate the inhibitory effect of targeting VEGF. Fluorescein fundus angiography (FFA) results showed that compared to the PBS control group, the area of vascular leakage was significantly reduced after Aflibercept treatment.


                        Figure 1. The efficacy test of Aflibercept on Cyagen's hVEGF mice.

3. The stable VEGFA mouse model

This self-developed hVEGF mouse model by Cyagen is driven by a bovine rod-specific (RHO) promoter to overexpress the coding sequence of the human VEGFA gene, allowing for overexpression of the human VEGFA protein specifically in the retinal rod cells. The rod cells in the eye will specifically overexpress Humanized VEGFA protein and develop wAMD Phenotype, like neovascularization. This transgenic mouse spontaneously develops significant vascular lesions while maintaining the integrity of the eye structure, making it suitable for drug evaluation and related mechanism research for neovascular eye diseases.

                    Figure 2. The construction method of hVEGF mice.

Cyagen's ophthalmology CRO platform is equipped with advanced instruments and a group of eye specialists and skilled technical personnel capable of conducting in vivo eye examinations. For the hVEGF mouse model, the platform can perform eye surface observation, intraocular pressure measurement, fundus photography, image-guided OCT, full-field electroretinogram ERG, and fluorescein fundus angiography FFA. Additionally, the platform has expertise in professional pathology and molecular detection techniques, including evaluation of VEGFA expression level in the retina, FITC-Dextran perfusion retinal flat mount, and VEGFA expression level in eye tissue sections, to assess the vascular lesion status. Some of the phenotype data are listed below:

a. Hematoxylin and eosin staining (HE staining) shows retinal area with neovascularization.

Figure 3. HE staining result

b. The hVEGF mice overexpress human VEGFA, but it does not affect the expression of the endogenous mouse VEGFA.

Figure 4. Detection of VEGF gene expression level in eyeball retina

c. The IB4 staining results showed abnormal and disorganized retinal blood vessel proliferation, and abnormal proliferation in the choroid region.

Figure 5. Isolectin GS-lB4 immunostaining

4. Recommendations for other ophthalmic models

In addition to the hVEGF (VEGFA overexpression) mouse model mentioned above, Cyagen has also developed a series of gene-edited and humanized mouse models for diseases such as retinal pigment degeneration, congenital achromatopsia, and complete color blindness. Cyagen also provides personalized services for researchers who require specific custom models to match their research needs.

Disease    Target Gene Gene Targeting Type
Macular degeneration
ABCA4(ABCR) KO、Humanization
Pigmentary degeneration of retina
RHO KO、CKO、Humanization、Humanization(Mu)
Mertk KO、CKO
Rpgr KO
Crb1 KO
Rd1(Pde6b) KO、MU
Rd10(Pde6b) MU
Retinal degeneration Tub KO
Late-Onset Retinal Degeneration Rds(Prph2) KO
Leber congenital amaurosis type 2 Rpe65 KO、MU
Leber congenital amaurosis type 4 Aipl1 KO
Leber congenital amaurosis type 10 CEP290 Humanization
Leber congenital amaurosis type 13 Rdh12 KO
Achromatopsia Cnga3 CKO
Fuchs endothelial dystrophy TCF4 CKO、Humanization
Congenital aniridia Pax6 CKO
Choroideremia  Chm CKO
Usher Syndrome 
USH2A Humanization
Myo7a CKO
Vitelliform macular degeneration Best1 KO
X-linked retinoschisis Rs1 KO、CKO
Oculocutaneous albinism type 1 Tyr CKO
Oculocutaneous albinism type 3 Tyrp1 KO、CKO
Wolfram Syndrome Wfs1 KO、CKO
Pseudoxanthoma elasticum Abcc6 KO、CKO


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