Osteoporosis Drug Stops Growth of Breast Cancer Cells

Osteoporosis Drug Stops Growth of Breast Cancer Cells

Medical researchers discovered a groundbreaking connection this week between a drug that treats osteoporosis and breast cancer.

A team of researchers at the Duke Cancer Institute made this discovery, which was presented June 15, 2013, at the 95th annual Endocrine Society meeting in San Francisco.

Their finding showed that the drug, bazedoxifene, which is approved in Europe for the treatment of osteoporosis can also stop the growth of breast cancer cells, even in cancers that have become resistant to current targeted therapies.

Bazedoxifene packs a powerful one-two punch that, not only prevents estrogen from fueling breast cancer cell growth, but also flags the estrogen receptor for destruction, according to the study.

“We found bazedoxifene binds to the estrogen receptor and interferes with its activity, but the surprising thing we then found was that it also degrades the receptor; it gets rid of it,” said senior author Donald McDonnell, PhD, chair of Duke’s Department of Pharmacology and Cancer Biology.

Currently, if breast cancer cells develop resistance to tamoxifen and/or aromatase inhibitors – two common drugs to treat breast cancer – patients are than usually treated with toxic chemotherapy agents.

This type of treatment has significant side effects including depression of the immune system, fatigue, gastrointestinal distress and tendency to bleed easily.

Bazedoxifene is a pill, like tamoxifen, but some of the properties of a newer group of drugs, known as selective estrogen receptor degrades (SERDs), 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 research scientist Suzanne Wardell, PhD, a research scientist in McDonnell’s lab.

Many investigators had assumed that once breast cancer cells developed resistance to tamoxifen, they would be resistant to all drugs that target the estrogen receptor, McDonnell explained.

“We discovered that the estrogen receptor is still a good target, even after it resistance to tamoxifen has developed,” McDonnell said.

Because 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 reported.

In clinical trail, the most common effect among the bazedoxifene treatment group was hot flashes.

This study was funded by a research grant from Pfizer Pharmaceuticals, maker of bazedoxifene. Pfizer is currently working with the FDA to determine exactly what research results are needed to approve this drug for breast cancer treatment.

Breast cancer is the second-most fatal type of cancer for women, according to the National Cancer Institute. They estimated that over 40,000 women will lose their battle with the disease and around 230,000 new cases will be diagnosed in 2013.

Catching cancer early gives patients more time to review their care options and to set up life insurance policies.