The results of a study of an experimental drug, T-DM1, part of a new class of cancer drugs, was presented in ASCO, Chicago, on Saturday, reports NY Times. The drug, T-DM1, delayed breast cancer progression without many of the side effects that usually accompany a chemotherapy treatment. The fusion drug delivers the medication to tumor cells directly without affecting healthy cells.
T-DM1 – Antibody Drug Conjugate
T-DM1 is being developed by Genentech and will apply for FDA approval of the same by the end of the year.
T-DM1 belongs to the group of antibody drug conjugates, which seem to be the current pulse of cancer treatment research. The toxins or medications to kill cancer cells are linked to proteins called antibodies. These antibodies recognize receptors on the surface of cancer cells and bind to them. Thus, when they enter the cells, they are broken down, releasing the toxin directly into the cancer cells. The toxins can act only once they are released into a cancer cell and hence are not harmful to normal cells of the body.
T-DM1 is specific for HER2 positive breast cancers. The antibody used in T-DM1 is Herceptin/Trastuzumab which is used for treating HER2 positive tumors. The ‘T’ in the T-DM1 drug is Trastuzumab and the ‘DM1’ denotes a toxin more lethal than usually used chemotherapy drugs. Trastuzumab recognizes HER2 proteins on surface of breast cancer cells. Trastuzumab linked to DM1 is taken into the cancer cells where the antibody is degraded and the toxin released.
ImmunoGen, Waltham, Mass, developed DM1 and the method for linking the antibody. T-DM1 is also known as trastuzumab emtansine and has an advantage of being relatively safe as claimed by investigators and experts.
Details of T-DM1 Clinical Trial
The clinical trial for investigating the drug was sponsored by Genentech.
- The trial involved 991 women with metastatic breast cancer.
- These patients had breast cancer which continued to worsen in spite of being treated with Herceptin and chemotherapy drug, taxane.
- Among the participants, half of them were administered T-DM1 and the other half were administered drugs – Tykerb or lapatinib and Keloda or Capecitabine. These drugs are the common routine treatment drugs prescribed for lung cancer patients.
- T-DM1 was found to delay worsening of disease by 3 months.
- The median time before progression of disease ensued for the T-DM1 group was 9.6 months while it was 6.4 months for the group receiving the other two drugs.
- 84.7% of patients receiving T-DM1 were alive after a period of one year while 77% of the control group was alive post one year.
- A hazard ratio measured in the trial, found that the risk of death reduced by 38% in patients on T-DM1.
- 40.8% of women taking T-DM1 had serious side effects while 57.8% of the control group suffered serious side effects.
- About 12.9% of patients on T-DM1 showed lowered blood platelet counts. This can increase risk of bleeding, however, investigators claim that actual cases of bleeding were not common.
T-DM1 has been found to be definitely safer and more effective than standard drugs. Dr. Kimberly L. Blackwell professor of medicine at Duke Cancer Institute and lead investigator of trial is quoted in New York Times,
This will be the largest survival benefit that we’ve ever seen in HER2-positive breast cancer.
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