Last Updated: 2003-06-02 15:55:20 -0400 (Reuters Health)
CHICAGO (Reuters Health) - Results of a phase I trial of an experimental immune-activating cancer vaccine indicates that the vaccine is safe and can generate a significant anti-tumor response in some patients with advanced cancer.
These results are "exciting," said Dr. John Marshall of the Lombardi Cancer Center in Washington, DC, who presented the findings Sunday during the 39th Annual Meeting of the American Society of Clinical Oncology.
The TRICOM vaccine uses either vaccinia or fowlpox as viral vectors carrying transgenes for carcinoembryonic antigen (CEA) found exclusively in a variety of cancer cells but not in normal cells. The latest version of the vaccine also expresses a triad of co-stimulatory molecules: B7-1, intercellular adhesion molecule-1 (ICAM-1), and leukocyte function-associated antigen-3 (LFA-3). "These three proteins improve the crosstalk between antigen-presenting dendritic cells and T cells," Dr. Marshall said.
Building on earlier pre-clinical studies with the TRICOM vaccine (See Reuters Health report Aug 7, 2000), Dr. Marshall's team tested it in 58 immunocompetent patients with advanced cancers who had not responded well to standard treatments. The majority of patients had colon cancer.
Patients received one of the following regimens: fowlpox TRICOM with monthly booster shots of the same vaccine; vaccinia TRICOM with boosters of fowlpox TRICOM; or vaccinia TRICOM with monthly boosters of fowlpox TRICOM plus granulocyte-macrophage colony-stimulating factor (GM-CSF).
All patients had significant CEA-specific T-cell responses. The best responses were seen in those receiving the vaccinia TRICOM plus fowlpox boosters and GM-CSF.
After two vaccinations, disease stabilized in 11 of the 58 patients, Dr. Marshall reported, but progressed in 47.
Because his team had "fairly significant" data from a prior study to suggest that four vaccinations might be needed for "maximum benefit", a subgroup of 25 patients went on to receive four vaccinations. Twelve of the 25 stabilized for at least 4 months, Dr. Marshall said. One patient had a radiographic complete response.
Side effects included mild fever, skin rash, and swelling of the lymph nodes.
Dr. Marshall told Reuters Health the TRICOM vaccine "may be applicable to a very broad population of patients -- GI cancers, breast cancers, lung cancers can potentially benefit from them." A phase II trial of the vaccine is underway in patients with colon and pancreas cancer.
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