Herceptin (also known as Trastuzumab) is a drug used to treat breast cancer.
Herceptin is a breast cancer treatment that blocks cancer-promoting proteins. Herceptin can be effective when given to the 20 to 30 percent of women whose tumors produce high levels of targeted proteins, and those women can be identified by genetic testing before treatment.
It reduces production of a protein from the HER2 gene, which is overexpressed ~25% of breast cancers. These "HER2-positive" tumors are associated with more rapid progression, decreased survival, and increased tumor recurrence. Trastuzumab blocks overexpression of HER2. Patients who had overexpression of the HER 2 genes responded to herceptin, whereas those without HER2 overexpression did not .