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Wednesday 26th June 2019

Genentech trials new breast cancer drug

5th June 2012

A new drug known as T-DM1 that combines Herceptin with a potent chemotherapy drug has been hailed as "magic bullet" in the treatment of breast cancer following recent clinical trials.


Doctors studying the drug say it could add valuable extra months to the lives of seriously ill patients.

Genentech, the company which is developing the drug, and which funded the trials, has said it plans to file for approval from the US Food and Drug Administration later in 2012.

Targeted cancer drugs often cost tens of thousands of dollars a month, although no cost has yet been set for the new drug, which homes in on cancer cells and has been found a recent late-stage study to delay the worsening of metastatic breast cancer.

It may also result in fewer side effects than traditional treatments, and delivers the cancer-killing active ingredient directly to the tumour without damaging nearby healthy cells.

Researchers divided a group of nearly 1,000 women with metastatic breast cancer that was continuing to get worse into two groups, giving one group T-DM1 and the other Tykerb and Xeloda, a standard treatment for women who aren't helped by Herceptin.

All of the women had seen their cancer continue to metastasise in spite of previous treatment with Herceptin and a common chemotherapy drug.

They found that the women in the group receiving T-DM1 experienced a delay in the time it took for the disease to progress further, averaging about three months.

The women in the T-DM1 group, on average, experienced a nine-and-a-half month delay in progression compared with a delay of about six-and-a-half months in the group that received the standard drugs.

According to Kimberly Blackwell of Duke University, they were also mostly spared the debilitating side-effects typically experienced with chemotherapy, which can include diarrhoea and vomiting, nausea and hair loss.

Just 1% of women on T-DM1 suffered a serious side effect compared with 57% of those in the group receiving standard treatment.

Researchers presented their preliminary findings at the annual meeting of the American Society of Clinical Oncology, but the results have yet to be published in a peer-reviewed scientific journal.

According to Blackwell, T-DM1 is based on trastuzumab, the scientific name for Herceptin, represented by the "T", while the "DM1" is derived from maytansine, a chemotherapy drug that is no longer used because of high toxicity levels.

In around 20% of breast cancer patients, the tumours are aggressive and test positive for the HER2 protein. Trastuzumab is a man-made antibody that binds to and blocks part of the HER2 protein that appears on the surface of some breast cancer cells.

However, many tumours eventually develop resistance, so the search is on for alternative treatment options for HER2 tumours.

Blackwell said T-DM1 would provide an important therapeutic option for patients with such tumours, and is the first combination therapy to link a potent anti-cancer agent to a targeted delivery system with an antibody.

According to Louis Weiner, director of the Lombardi Comprehensive Cancer Centre at Georgetown University in Washington, T-DM1 works like a Trojan horse that is welcomed into the cell while hiding something that is toxic to the cell.

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