Angiogenesis is the process of creating new blood vessels. Some cancerous tumors are very efficient at creating new blood vessels, which increases blood supply to the tumor and allows it to grow rapidly.
Cancer cells begin the angiogenesis process by sending signals to nearby tissue and activating growth factors that allow the tumor to form new blood vessels. One such molecule is called vascular endothelial growth factor, or VEGF.
Researchers developed drugs called angiogenesis inhibitors, or anti-angiogenic therapy, to disrupt the growth process. These drugs search out and bind themselves to VEGF molecules, which prohibits them from activating receptors on endothelial cells inside blood vessels. Bevacizumab (Avastin®) works in this manner. It is used to treat glioblastoma and cancers of the lung, kidney, breast, colon and rectum.
Other angiogenesis inhibitor drugs work on a different part of the process, by stopping VEGF receptors from sending signals to blood vessel cells. These drugs are known as tyrosine kinase inhibitors (TKI). Sunitinib (Sutent®) is an example of a tyrosine kinase inhibitor.
While angiogenesis inhibitors work to cut off the tumor’s blood supply, they do not destroy the tumor itself. For this reason, these drugs are typically used in combination with chemotherapy or other treatments.
Since they act on blood vessel formation and not the tumor itself, the side effects of angiogenesis inhibitors are different than traditional chemotherapy drugs.
Possible side effects include:
- High blood pressure (hypertension)
- Wounds that are slow to heal
- Increased risk of internal bleeding
- Perforation of the intestine (rare)