PHILADELPHIA A therapeutic cancer vaccine has shown effectiveness when given alongside chemotherapy to patients with metastatic colorectal cancer in a phase II trial, according to researchers at Oxford BioMedica (UK) Ltd. The study found that six of the 17 metastatic colorectal cancer patients in the study showed tumor shrinkage, classified as complete or partial responses following independent expert review.
The study, reported in the August 1 issue of Clinical Cancer Research, a journal of the American Association for Cancer Research, was designed to demonstrate the safety and immunogenicity of the vaccine, called modified vaccinia Ankara-encoding 5T4 (TroVax), when used alongside standard chemotherapy. The research was funded by Oxford BioMedica which is developing the vaccine in partnership with Sanofi-Aventis.
Unlike preventative vaccines, such as the human papillomavirus vaccine to prevent cervical cancer, TroVax is a therapeutic vaccine, designed to stimulate the immune systems of patients who already have cancer. The vaccine consists of an attenuated (non-disease causing) version of the vaccinia virus modified to deliver the gene for 5T4, a protein found in many tumors.
The idea is that the modified virus enters cells, produces the tumor protein and stimulates the immune system, said lead study author Richard Harrop, Ph.D., vice president of clinical immunology at Oxford BioMedica. 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.
The target of this immuno-therapy approach is a tumor antigen called 5T4, a protein embedded within the membrane of cancer cells. The protein is rarely found in normal tissues, but is produced at high levels by a wide range of human cancers, including colorectal, renal, gastric and ovarian. The
Contact: Greg Lester
American Association for Cancer Research