Prior to the introduction of trastuzumab, the first targeted anti-HER2 agent, in 1998, patients diagnosed with HER2-positive breast cancer felt like they were being handed a death sentence. Despite treatment with aggressive chemotherapy, their tumors recurred faster, more often spread to brain and liver, and were associated with higher rates of death than HER2-negative tumors. HER2-positive breast cancer was also more prevalent in younger patients, making the diagnosis even more devastating. However, in the 1980s, cancer researcher Axel Ullrich, PhD, and oncologist Dennis Slamon, MD, PhD, recognized that HER2 could be targeted by a small molecule that binds to the receptor on the cell surface and blocks the signal telling the cell to divide. This small molecule was called trastuzumab, and it eventually completely changed how HER2-positive breast cancer was treated.