Cancer vaccines have demonstrated that they can stimulate antibody and cell-mediated immune responses against tumor-associated antigens in the laboratory. However, few clinical studies with cancer vaccines have demonstrated convincing clinical responses. Sialyl-Tn is a carbohydrate associated with MUC1. It is a unique tumor-associated antigen, present on many adenocarcinomas including breast, ovarian, colorectal, gastric and pancreatic. Consequently, Sialyl-TN is an ideal candidate for boosting the patient's immune system specifically against a unique tumor-associated antigen. The cancer vaccine Theratope was developed by Biomira, Inc. using a synthetic Sialyl-Tn antigen that emulates the unique carbohydrate on human cancer. Clinical trials have predominantly been carried out in breast cancer patients and these trials are outlined in this profile.