A revolutionary new anticancer agent, trastuzumab [‘Herceptin’; Genentech], which works against the most aggressive types of breast cancer was highlighted at the 34th Annual Meeting of the American Society of Clinical Oncology [Los Angeles, US; May 1998]. Trastuzumab is a humanised monoclonal antibody that was rationally designed to target the growth factor receptor HER2/neu.If it is approved by the US FDA it will be the first biological treatment for HER2-overexpressing metastatic breast cancer, an aggressive form of the disease that is associated with rapid disease progression and shortened survival. Final results from 2 major clinical trials showed that trastuzumab has activity when administered either as monotherapy or in combination with standard chemotherapy regimens.