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New Drug Combination Offers Hope in Breast Cancer Treatment

Doctors today will unveil the results of the first large trial of a new kind of “precision medicine” against breast cancer: a drug combination designed to act like a smart bomb, which delivers its payload directly to tumor cells while reducing collateral damage to the rest of the body.

The experimental drug, T-DM1, doesn’t cure anyone.

But it attacks breast cancer in a whole new way — one that may be useful against a variety of other tumors — and appears significantly better at controlling cancer than the current standard of care, says Kimberly Blackwell, who presents her findings today in Chicago at the annual meeting of the American Society of Clinical Oncology.

T-DMI combines the drug Herceptin, a man-made antibody, with an old-fashioned chemotherapy drug called emtansine, Blackwell says.

Herceptin, approved in 1998, was designed to block growth signals from a protein found almost exclusively on cancer cells called HER2, says Sandra Horning, global head of development at Genentech, the drug’s developer. Herceptin homes in on HER2 proteins, binds to them and blocks them from transmitting run-away growth signals. To create T-DM1, scientists attached chemotherapy molecules to Herceptin, hanging them like ornaments on a Christmas tree. When T-DM1 is infused into the body, Herceptin zeroes in on HER2 proteins and releases its “payload” of toxin directly at the cancer cell. The toxin then enters the cancer cell and kills it, Horning says.

That’s a big change from traditional chemo, in which controlled doses of poison are infused into the bloodstream. While chemo kills cancer cells, it also kills healthy tissues, too, often causing grueling side effects of nausea, vomiting and fatigue, as well as life-threatening infections.

Doctors tested T-DM1 in a study of nearly 1,000 women with advanced cancers who had been on Herceptin, but who are no longer benefiting from it. All of the women had breast cancers that make lots of HER2.

T-DM1 kept these women’s cancers in check for 9.6 months, about three months longer than standard therapy, which combines the anti-cancer pills Tykerb and Xeloda, according to the study.

Doctors also noticed a trend suggesting that women randomly assigned to take T-DM1 live longer, as well. After two years, 65% of those on T-DM1 were alive, compared to 48% of those on Tykerb and Xeloda.

“It’s a major advance,” says Jo Anne Zujewski, a breast cancer researcher at the National Cancer Institute, who was not involved in the study. “I’m excited for women.”

To read the entire story by Liz Szabo, go to USA Today

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