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Monoclonal Antibodies
Bevacizumab (Avastin®)
Bevacizumab (Avastin®) is an injectable monoclonal antibody that neutralizes a key angiogenesis-stimulating protein called vascular endothelial growth factor (VEGF). A major phase 3 clinical trial, known as E2100, conducted in metastatic breast cancer patients compared the combination of bevacizumab and paclitaxel, a taxane chemotherapy, to paclitaxel alone.3 Patients in this study were required to have breast cancer negative for human epidermal growth factor receptor-2 (HER-2), and could not have received prior breast cancer treatments.

The findings were dramatic: those who received the bevacizumab-paclitaxel combination lived twice as long without their disease worsening, known as progression-free survival, compared with patients who just received paclitaxel alone: 12 months compared with 6 months. Further, nearly half of women who received the bevacizumab-paclitaxel combination had their tumors shrink, compared with just over 20% of women who received single-agent paclitaxel.4

Based on these results, in February 2008 the U.S. Food and Drug Administration (FDA) granted accelerated approval for bevacizumab, in combination with paclitaxel, for the treatment of HER-2-negative metastatic breast cancer in patients who have received no prior treatment. Accelerated approval means that the FDA has granted preliminary approval for a drug for a specific indication pending more comprehensive data.

In July 2010, an independent panel that advises the FDA on cancer drugs recommended that the breast cancer indication for bevacizumab be revoked, citing more recent clinical data indicating that the potential risks of the drug, which can include side effects such as high blood pressure and bleeding, outweighed the benefits. A key factor in the panel’s decision was data from newer studies showing that bevacizumab slowed disease progression by only about a month, and did not help women live longer overall. The FDA accepted the panel's decision in December 2010.

In an unusual move, the manufacturer of bevacizumab appealed the FDA’s decision, which culminated in public hearings at the FDA in June 2011. During these hearings, breast cancer patients, oncologists, and advocacy groups argued that bevacizumab provided meaningful benefits, including improved quality of life and, in some cases, prolonged the lives of women with metastatic breast cancer for many months. Ultimately, however, the acting FDA Commissioner officially announced in November 2011 that the breast cancer labeling for bevacizumab was rescinded. Many private insurance companies, as well as the government-run health program Medicare, have indicated that for the time being they will continue to cover bevacizumab for breast cancer.

The manufacturer of bevacizumab is conducting an additional study of bevacizumab paired with the chemotherapy drug paclitaxel in patients with previously untreated metastatic breast cancer. The clinical trial includes a panel of pre-specified biomarkers that may help to better define which patients could most benefit from treatment with bevacizumab. Clinical trials are still the best way for breast cancer patients to gain access to experimental therapies, including antiangiogenic agents.


Last updated January 30, 2012