Some breast cancer cells make (overexpress) too many copies of a particular gene known as HER2. The HER2 gene makes a protein known as a HER2 receptor. HER2 receptors are like ears, or antennae, on the surface of all cells. These HER2 receptors receive signals that stimulate the cell to grow and multiply. But breast cancer cells with too many HER2 receptors can pick up too many growth signals and so start growing and multiplying too much and too fast. Breast cancer cells that overexpress the HER2 gene are said to be HER2-positive. About one out of every four breast cancers is HER2-positive.
Kadcyla is a combination of Herceptin and the chemotherapy medicine emtansine. In Kadcyla, the emtansine is attached to the Herceptin.
Herceptin is approved by the U.S. Food and Drug Administration (FDA) to treat advanced stage, HER2-positive breast cancers and to lower the risk of recurrence of early-stage, HER2-positive breast cancer with a high risk of recurrence. Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals.
Emtansine, like some other chemotherapy medicines, disrupts the way cells grow. Emtansine isn’t a targeted medicine, which means it can affect healthy cells as well as cancer cells. Emtansine is never given alone to treat any type of cancer because it is too toxic.
Kadcyla was designed to deliver emtansine to cancer cells in a targeted way by attaching emtansine to Herceptin. Herceptin then carries emtansine to the HER2-positive cancer cells. This way, the emtansine is less toxic to healthy cells and more effective in treating cancer cells.