Experimental Regimen May Work Against Treatment-Resistant Breast Cancer

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A preliminary study looked at how advanced-stage, HER2-positive breast cancer tissue transplanted into mice responded to a combination of two experimental treatments:

  • T-DM1 (chemical name: ado-trastuzumab emtansine), a targeted therapy made up of Herceptin (chemical name: trastuzumab) attached to the chemotherapy medicine DM1 (chemical name: maytansine); when one medicine is attached to another, it's called "conjugated"
  • Omnitarg (chemical name: pertuzumab), another targeted therapy

The cancer tissue transplanted into the mice came from women who had stopped responding to all standard treatments for advanced-stage, HER2-positive breast cancer.

These results were reported at the 2010 American Association for Cancer Research annual meeting.

Herceptin is approved by the U.S. Food and Drug Administration to treat advanced-stage, HER2-positive breast cancer and to lower the risk of recurrence of early-stage, HER2-positive breast cancer with a high risk of recurrence. HER2-positive cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. About one out of every four breast cancers is HER2-positive. Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals.

DM1 disrupts the way cells grow. By itself, DM1 isn't considered a targeted therapy, which means it can affect healthy cells as well as cancer cells. By attaching DM1 to Herceptin to make T-DM1, the researchers hoped to deliver the chemotherapy only to cancer cells.

Omnitarg stops the HER2 protein from telling cancer cells to grow.

It's important to know that both T-DM1 and Omnitarg are experimental medicines and neither one is approved to treat breast cancer.

Cancers in mice treated with only T-DM1 or with only Omnitarg did not respond to treatment. Cancers in mice treated with the combination of T-DM1 and Omnitarg did respond to treatment.

This study was preliminary and done in mice, not people. Still, the results are encouraging, especially since the cancers transplanted into the mice had stopped responding to many other treatments. Researchers now are studying the combination in clinical trials.

If you're being treated for advanced-stage, HER2-positive breast cancer, you and your doctor may be considering several treatment options, especially if the cancer has stopped responding to standard treatments. If you're willing to participate in a clinical trial, you may have even more options available. Talk to your doctor about clinical trials that might be a good fit for you and your unique situation. You can visit the Breastcancer.org Clinical Trials pages for more information.

And stay tuned to Breastcancer.org to learn about the latest research on new, better ways to treat breast cancer.

Editor’s Note: On Feb. 22, 2013, the U.S. Food and Drug Administration (FDA) approved Kadcyla (chemical name: T-DM1 or ado-trastuzumab emtansine). In some early studies of T-DM1, such as the study reviewed here, it was reported that the chemotherapy medicine maytansine was attached to Herceptin to form T-DM1. Emtansine is a derivative of maytansine. In June 2012, the FDA approved using the targeted therapy medicine Perjeta (chemical name: pertuzumab) in combination with Herceptin (chemical name: trastuzumab) and Taxotere (chemical name: docetaxel) to treat HER2-positive, metastatic breast cancer that hasn’t been treated with either Herceptin or chemotherapy yet. (Perjeta was called Omnitarg in earlier studies.)On May 3, 2019, the FDA approved Kadcyla to treat early-stage HER2-positive breast cancer after surgery if residual disease was found after neoadjuvant treatment with taxane chemotherapy and Herceptin.


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