Many new biotherapy agents to treat cancer are being studied as single agents and in combination with conventional cancer therapy, such as chemotherapy. These agents include the monoclonal antibodies, rituximab, trastuzumab, alemtuzumab and IMC-C225. Radioimmunotherapy, a type of biotherapy that combines a radioactive isotope with a monoclonal antibody, also is being studied and has shown promise in the treatment of lymphoma. A tyrosine kinase inhibitor. STI 571, has been approved recently by the U.S. Food and Drug Administration. Several vaccines as cancer treatment are currently under investigation. Other biotherapy agents being investigated include angiogenesis inhibitors, such as endostatin. antivascular endothelial cell growth factor and thalidomide, an agent that inhibits the formation of blood vessels that supply tumors.