By Rebecca Olson, Life Science Research Assistant, Stanford Cancer Institute and Breast Cancer Connections Volunteer
The FDA recently approved a breakthrough cancer drug that represents an exciting new direction in breast cancer treatment. T-DM1 (Kadcyla, Roche) is the first “armed antibody” on the market. This novel antibody-drug conjugate allows for the targeted delivery of chemotherapy to cancer cells without producing concurrent toxic effects on normal cells. The T-DM1 conjugate consists of a stable linkage between the well-known antibody trastuzumab (Herceptin) and the chemotherapeutic molecule DM1 (emtansine)1. This new drug holds great promise for many patients with HER2-positive breast cancer, and has opened the floodgates for a new wave of cancer research.
Chemotherapeutic drugs cause damage by impairing cell division, and produce cytotoxicity in fast-dividing cells like those in tumors. Many other types of cells are susceptible—including those responsible for hair growth and intestinal lining—leading to severe side effects. T-DM1 was developed by Roche (Genentech) and represents a major step in the creation of safer chemotherapy drugs. Trastuzumab (Herceptin) works by binding to the HER2 protein on the surface of tumor cells, slowing the cell’s growth and marking it for destruction by immune cells2. With T-DM1 treatment, the trastuzumab antibody still binds the tumor cell but also delivers a toxic chemo payload. “Kadcyla is an antibody-drug conjugate representing a completely new way to treat HER2-positive metastatic breast cancer, and it helped people in the EMILIA study live nearly six months longer,” said Hal Barron, Roche’s chief medical officer and head of global product development3.
The EMILIA study specifically looked at a patient population of 991 women with metastatic or locally advanced HER2-positive breast cancer. These patients had previously been treated with a standard treatment regimen of Herceptin and a taxane chemotherapy, but had stopped responding to therapy. Half of the women received T-DM1 and the other half received another HER2-blocking drug, lapatinib (Tykerb) in addition to the chemotherapeutic agent capecitabine (Xeloda)4. T-DM1 recipients survived longer without disease and experienced far fewer side effects than those who received the standard of care. Incidences of low platelet count and increased liver enzyme levels were higher with T-DM1; side effects that were higher with lapatinib plus capecitabine included diarrhea, nausea, vomiting, and low red blood cell count. In addition, and particularly important to patients, treatment with T-DM1 is not associated with significant hair loss5.
T-DM1 is currently FDA approved as a second line therapy for HER2+ metastatic disease, but ongoing trials will determine its use as a first line therapy and perhaps in early-stage breast cancer. In short, T-DM1 is a promising new therapy for patients with advanced breast cancer. It is the first such antibody-drug conjugate explored in breast cancer, and will certainly shape future research into exciting new cancer treatments.