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Vascular endothelial growth factor (VEGF) is a molecule produced by the body when it requires the formation of new blood vessels. The production of VEGF is necessary for many normal physiological processes, including blood vessel growth in the fetal stages, during injury healing, or for the growth of new vessels in tissues that have a deficient blood supply. VEGF is also involved in pathological processes in the body, like the development of a blood supply in tumors that allows for growth and spread of the tumor, or the formation of new blood vessels in the eye that can eventually result in vision loss, also known as wet macular degeneration. Anti-VEGF therapies therefore aim to prevent this abnormal blood vessel formation by blocking VEGF action.
There are two widely available anti-VEGF therapies. A commercially produced antibody is a molecule generated against a specific peptide. In general, these antibodies specifically bind to the peptide of interest and prevent its specific action. Several of these antibodies are well-known, including bevacizumab, or Avastin, and ranibizumab, or Lucentis.
A second type of anti-VEGF therapy includes molecules that inhibit the activation of compounds that are downstream of VEGF in the blood vessel-inducing physiological pathway. By inhibiting these compounds, it is possible to block the signals sent out by VEGF. Both of these therapies may be used to inhibit tumor metastasis or slow down tumor growth, or to slow down the progression of wet macular degeneration.
Tumors, or solid cancers, can only grow to a certain point before they require a blood supply. When these tumors require a blood supply, some of the cancer cells may begin to secrete VEGF into the tumor environment so new blood vessels will form. In these types of tumors, anti-VEGF therapy may contain the size of the tumor and possibly stop it from spreading. Unfortunately, at some point the tumors are often able to start growing again even in the presence of anti-VEGF therapy, and therefore the effect of this therapy is not always long-lasting.
In wet macular degeneration, the growth of blood vessels into the normally clear cornea and retina can lead to loss of sight. This condition can be treated, or at least slowed down, with anti-VEGF therapy. To treat this condition, the anti-VEGF molecule often must be injected into the eye, and these injections are usually required on a monthly basis. The immediate side effects associated with this therapy are due to the injection rather than the treatment, and often involve soreness at the injection site and risk of infection.
The long-term side effects of anti-VEGF therapies are not entirely clear because the drugs are relatively new. These side effects would be expected to involve adverse effects from lack of VEGF signaling, such as slowed or poor wound healing, or difficulty growing new blood vessels to replace blocked areas. For most people, however, any such side effects are worth the risk when faced with blindness or a rapidly growing tumor.
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