5T4 vaccine appears promising in metastatic colorectal ca

OXFORD, United Kingdom—A gene-based therapeutic cancer vaccine given along with standard chemotherapy produced tumor shrinkage in 6 of 11 evaluable patients with metastatic colorectal cancer. Results of the phase II trial were reported in the August 1 issue of Clinical Cancer Research (13:4487-4494, 2007).

The vaccine (TroVax) consists of an attenuated strain of vaccinia virus, modified vaccinia Ankara (MVA), encoding the tumor antigen 5T4, which is found on the surface of most solid tumor cells but not on normal cells. In colorectal cancer, 5T4 is expressed on approximately 85% of tumors.

"The idea is that the modified virus enters cells, produces the tumor protein, and stimulates the immune system," said lead author Richard Harrop, PhD, vice president of clinical immunology at Oxford BioMedica, which is developing the vaccine along with sanofi-aventis. "To give a vaccine alongside chemotherapy might seem counterintuitive, since chemotherapy can weaken the immune system, but our study shows that Trovax could be complementary to standard chemotherapy, enhancing the immune response to tumors."

Vaccine was given to 17 patients with metastatic colorectal cancer just before, during, and after treatment with standard chemotherapy (FOLFOX). Eleven patients received the complete course (6 injections), and 10 of these mounted a potent immune response to the 5T4 tumor protein. Six patients responded, including one complete response. A phase III study in renal cancer is ongoing,