The Promise of Avastin

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Manhattan Eye, Ear & Throat Hospital
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The Promise of Avastin

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Excerpt from a report by Richard Spaide, MD
-Attending Surgeon, Manhattan Eye, Ear & Throat Hospital and Vitreous-Retina-Macula Consultants of NY

Avastin (Bevacizumab) is a drug designed to inhibit the growth of blood vessels. It was initially developed to treat cancer. In order to grow, cancer cells need food and oxygen delivered by blood vessels. Cancer causes new blood vessels to grow. If we can stop the blood vessels from growing, then we may be able to slow the growth of cancer.

Avastin has been used in a variety of cancers with good effect and its use as a drug, given by intravenous injection, was approved by the United States Food and Drug Administration (FDA). Avastin binds to a chemical released by cells, called Vascular Endothelial Growth Factor (VEGF). VEGF is a protein that promotes cell growth in the human body. Macular degeneration is caused, in part, by abnormal growth of blood vessels under the macula. Because Avastin blocks the growth of new vessels in cancer patients, it has been used in patients with macular degeneration, with positive results.

Because we want the effect only in the eye, injection of the drug into the eye would allow us to target the drug, using an extremely small dose. This is the basis of intravitreal (injection into the eye) Avastin. When we give Avastin directly into the eye, we use about 1/500th of the intravenous dose. The injection delivers the drug directly into the eye, bypassing systemic circulation. While Avastin is approved by the FDA for cancer treatment, its use for macular degeneration is what is called an "off-label application".

In our practice, we have given some 1,200 injections so far. We have not seen much in the way of any significant intraocular or systemic problems in our patients. We are constantly on the lookout for these problems because of safety concerns. Other practices around the country have also given large numbers of Avastin injections and have anecdotally reported similar positive experiences. By contrast, cancer patients being treated with intravenous Avastin while undergoing chemotherapy sometimes suffered serious side effects. These included blood clots, hypertension and nose bleeds.

In our patients with macular degeneration, we have seen a significant proportion that have either stabilized or shown improvement of visual acuity after injection of Avastin into the eye. We see secondary improvement in the results of tests that we commonly perform, such as fluorescein angiography and optical coherence tomography (OCT). We have not had such positive experiences before in treating macular patients. We have also had good results in patients with central retinal vein occlusion and proliferative diabetic retinopathy.

Although this drug seems to be a miracle of sorts, the company that makes it, Genentech, is putting its efforts behind another drug for use in the eye called Lucentis. The aims of Lucentis and Avastin are the same Ð namely, to bind VEGF. This is not surprising, because Lucentis and Avastin are essentially the same drug. Lucentis is a fragment of Avastin. Compare a grain of table salt with a grain of sea salt. Lucentis, developed as a specific product for the eye, has been undergoing clinical trials for some time, with positive results. Because of these results, Genentech has applied for FDA approval for Lucentis.

Avastin is still a new drug and many doctors are working on evaluating its ability to work in the eye. Publication of these results will help everyone understand the risks and benefits of intravitreal Avastin. Until published results exist, Medicare will not pay for Avastin injections, so the cost is out of pocket.