CHICAGO (Reuters) - U.S. researchers may have found a way to overcome resistance to hormone-blocking breast cancer drugs, extending the life of treatments that keep the disease in check.
They said the drug Nexavar or sorafenib, made by German drugmaker Bayer and its development partner Onyx Pharmaceuticals, helped re-sensitize breast cancer to treatment with aromatase inhibitors, drugs given to post-menopausal women with hormone-sensitive breast cancers.
“Hormone-receptor positive breast cancers eventually become resistant to hormonal therapy,” said Dr. Claudine Isaacs of Georgetown University in Washington, who presented her findings at the American Association for Cancer Research’s San Antonio Breast Cancer Symposium.
“There has been a great deal of interest in trying to figure out how we might overcome that resistance or stop the cancer cells from figuring out how to circumvent that hormonal therapy,” Isaacs said in a telephone interview.
She said Nexavar, a drug approved for liver and kidney cancer, acts on a lot of cancer-related genes and it also acts to inhibit new blood vessels from forming.
The researchers studied the drug in 35 post-menopausal women with advanced breast cancer resistant to treatment with aromatase inhibitors.
Women in the trial, funded with a grant by Bayer, continued to take the aromatase inhibitor, but they also took Nexavar.
“These women all had disease progression. Twenty-three percent of the women in the study had a clinical benefit from it. It means they either had shrinkage of their tumors or it stayed stable,” Isaacs said.
Isaacs said the finding suggests the drug somehow circumvents the mechanism used by the cancer to resist the effects of the aromatase inhibitors.
“It puts the brakes on it so it didn’t grow for at least six months,” she said.
The treatment was not without side effects. Many women in the study developed a rash called hand-foot syndrome, which causes redness, peeling and some tenderness on the palms of the hands and soles of the feet.
It also caused elevated blood pressure in 11 percent of the women, but Isaacs this could be overcome by putting women on blood pressure drugs before taking Nexavar.
She said the findings were strong enough to inspire the drug companies to start a large, late-stage study to see if it has a significant benefit for women.
Aromatase inhibitors include anastrozole, made by AstraZeneca under the brand name Arimidex, and exemestane, made by Pfizer Inc, under the brand name Aromasin.
Breast cancer is the second-leading cause of cancer death among U.S. women, after lung cancer. It kills 500,000 people globally every year.
Editing by Paul Simao
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