Avastin is the brand name for the drug which is called bevacizumab. Avastin is one of several anti-VEGF treatments that are injected into the eye. Anti VEGF drugs block the growth of abnormal blood vessels in the back of the eye. These blood vessels can leak and affect vision, causing vision loss from wet AMD and diabetic eye disease.
Avastin was first approved by the Food and Drug Administration (FDA) to treat different types of cancer. If Avastin is an anti cancer drug, how is it used in the eye?
After approval of bevacizumab for cancer therapy and given the suspected role of VEGF in neovascular AMD (NVAMD), intravenous bevacizumab began to be administered to treat wet AMD in the eye, as off-label use.
A small uncontrolled study showed significant improvement in visual acuity, retinal thickness on optical coherence tomography, and angiographic outcomes. After 12 weeks of therapy, visual acuity improved by 8 and 12 letters. Soon after, ophthalmologists began injecting bevacizumab directly into the vitreous cavity as an off-label use in the treatment of wet AMD. Intravitreal injection of Avastin was found to be effective in the treatment of NVAMD, with minimal systemic adverse effects, which led to the first studies to demonstrate an improvement in visual function in patients with wet AMD.
While the other anti-VEGF injections have received FDA approval for intravitreal use, Avastin still isn’t FDA approved, Its use to treat eye disease is considered “off-label” use. The FDA allows “off-label” drug use if doctors are well informed about the product and studies prove the drug is helpful. Avastin continues to be used off-label for a variety of ophthalmic conditions like Wet ARMD, and macular edema due to diabetic retinopathy and retinal vein occlusions.
What is Wet ARMD?
ARMD stands for Age-Related Macular Degeneration. It is of 2 types :
In Wet ARMD there is the formation of a neovascular membrane at the macula, which causes leakage of fluid and/or bleeding into the retina. This can cause a sudden drop in vision, or cause distortion of images. This leakage is treated by giving intravitreal Anti VEGF injections into the eye. If left untreated it can progress to scar formation and result in permanently low vision.
In Dry ARMD there is no leakage of fluid, however, the macula can thin out and become atrophied. There is currently no known treatment to stop the progression to atrophy, however, multivitamins can slow down the progression.
What is Macular Edema?
Macular edema is swelling or collection of fluid in the central part of the retina. The fluid collection occurs due to 2 main reasons :
Vascular component – Due to release of VEGF by the diseased retina. This effect of VEGF is counteracted by anti-VEGF drugs like Accentrix, Avastin, and Eylea.
Inflammatory component – The diseased retina also releases different inflammatory mediators, which contribute to the swelling. This inflammatory component is treated by giving intravitreal steroids.
Swelling or fluid collection at the macula is commonly seen in Wet Age-Related Macular Degeneration, Diabetic Macular Edema, and Retinal Vein Occlusions.
How does Avastin work?
Bevacizumab (Avastin) is a recombinant humanized monoclonal IgG1 antibody. Bevacizumab binds to the receptor-binding site on VEGF, which inhibits the binding of VEGF molecules to their receptors on the surface of endothelial cells. It basically prevents the VEGF molecule from having its desired effect, and thus, blocks the growth of abnormal blood vessels in the back of the eye.
How is Avastin different from Accentrix?
Avastin (Bevacizumab) was the first anti-VEGF used for the treatment of eye conditions. Though it hasn’t been FDA approved, off-label use continues for a variety of ophthalmic conditions.
The active part of the molecule is similar in Avastin (bevacizumab) and Accentrix (Ranibizumab). However, bevacizumab is the whole anti-VEGF antibody (150 kD), while ranibizumab is an antibody fragment. Bevacizumab has a longer half-life in the systemic circulation than ranibizumab while ranibizumab is believed to penetrate the retina better and has a higher affinity to VEGF-A than bevacizumab. These differences could have an impact on the safety and efficacy of these drugs.
Because Avastin use is off label for the eye, it is available in higher concentrations, from which the individual intravitreal injections need to be prepared. Multiple injections are prepared from the same vial, and this does carry a minimal risk of infection as compared to the other Anti VEGF which are available in single-use vials specially designed for use in the eye.
The cost of one injection of Avastin is approximately 1/3rd that of Accentrix.
Even though it isn’t FDA approved, Avastin has almost similar efficacy as Ranibizumab and continues to be the injection of choice for those who cannot afford the more expensive Anti VEGF injections.
How is Avastin different from Ozurdex?
Avastin is an intravitreal Anti-VEGF injection, which treats macular edema by blocking VEGF.
Ozurdex is an intravitreal steroid implant, which continues to release steroid (dexamethasone) gradually into the eye over several weeks. This steroid treats the inflammatory component in macular edema.
The effect of Avastin lasts for 4-6 weeks while ozurdex lasts for 4-6 months. However, Ozurdex is associated with the risk of causing raised eye pressure and cataracts, which is rare with Avastin. Also, ozurdex does not work in Wet ARMD.
In patients with diabetic macular edema and retina vein occlusions, the protocol is to start treatment with an anti-VEGF, and then switch to ozurdex if the anti VEGF injections do not have the desired result.
Who should receive Avastin?
Avastin is currently the cheapest anti-VEGF injection available and is similar in efficacy to Accentrix. It continues to be the injection of choice for those who cannot afford the more expensive Anti VEGF injections.
For which eye conditions can Avastin be used
Avastin can be used for the treatment of Choroidal Neovascular membranes (CNVMs) associated with Age-related macular degeneration ( wet ARMD), Macular edema due to diabetic retinopathy and vein occlusions, postoperative cystoid macular edema, regression of neovascularization in proliferative diabetic retinopathy and neovascular glaucoma, CNVMs associated with myopia or choroiditis, and Retinopathy of Prematurity ( ROP).
What is the dose of Avastin?
The current dosing schedule is 0.05 ml (1.25mg) given once a month.
Does Avastin injection need to be repeated?
The general dosing schedule is to start with 3 injections given 1 month apart, and then monitor the retinal swelling and vision, and decide for further injections. Actual treatment protocols vary, but may include strict monthly administrations, or on an “as needed” basis.
What are the side effects of Avastin injection?
As with any intraocular injection, there are some risks. The most commonly reported adverse reactions (>10%) included conjunctival hemorrhage, vitreous floaters, vitreous detachment, increased intraocular pressure, and eye pain. These occasionally occur with any intravitreal injection.
Severe complications are rare, and include:
- retinal detachment
It is rare to lose vision as a result of an intravitreal injection. But if you do develop any of these Red Flag signs, then we recommend that you call our clinic immediately.
- Severe, constant pain
- New worsening pain after the first day
- Significant decrease in vision
- Severe, constant floaters
- Curtain or veil in your vision
What happens after Avastin injection?
Right after the injection, the eye is patched after putting an antibiotic eye ointment. The patch can be removed after 2 hours and antibiotic eye drops are started. Usually, the doctor will see you after 3-4 weeks when an OCT scan will be repeated to see the swelling in the retina.