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Osteoporosis Therapy Stops Growth of Breast Cancer Cells
A drug approved in Europe to treat osteoporosis has been shown to stop the growth of breast cancer cells, even in cancers that have become resistant to current targeted therapies, according to a new study from the Duke Cancer Institute in Durham, N.C.
The findings, presented June 15 at the annual Endocrine Society meeting in San Francisco, indicate that the drug bazedoxifene packs a one-two punch that not only prevents estrogen from fueling breast cancer cell growth, but also flags the estrogen receptor for destruction.
In animal and cell-culture studies, the drug inhibited growth both in estrogen-dependent breast cancer cells and in cells that had developed resistance to the anti-estrogen drug tamoxifen and/or to the aromatase inhibitors, two of the most widely used types of drugs to prevent and treat estrogen-dependent breast cancer. If breast cancer cells develop resistance to these therapies, patients are usually treated with toxic chemotherapy agents that have significant side effects.
Bazedoxifene, like tamoxifen, is a specific estrogen receptor modulator (SERM). Drugs in this class are distinguished by their ability to behave like estrogen in some tissues, while significantly blocking estrogen action in other tissues. But unlike tamoxifen, bazedoxifene has some of the properties of a newer group of drugs, known as selective estrogen receptor degraders (SERDs), which can target the estrogen receptor for destruction.
“Because the drug is removing the estrogen receptor as a target by degradation, it is less likely the cancer cell can develop a resistance mechanism because you are removing the target,” said lead author Suzanne Wardell, PhD.Since bazedoxifene has already undergone safety and efficacy studies as a treatment for osteoporosis, it may be a viable near-term option for patients with advanced breast cancer whose tumors have become resistant to other treatment options, Wardell said. In clinical trials, the most often reported side effect was hot flashes in the bazedoxifene treatment groups.
Source: Duke University; June 15, 2013.