Herceptin, or trastuzumab, is a monoclonal antibody used mainly to treat HER2-positive breast and gastric cancers. HER2 is a protein that promotes cancer cell growth, and cancers with high HER2 levels tend to be more aggressive. Herceptin targets and binds to HER2 receptors on cancer cells, blocking their growth and helping the immune system destroy them. It is often used alone or alongside...