Promising results witnessed in cancer vaccine tests
Promising results were witnessed in cancer vaccine tests
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Friday, 24, Oct 2008 12:01
Research on a new cancer vaccine has shown it is capable of obtaining an immune response in most patients with bowel, kidney and prostate cancer.
At a news briefing on cancer therapies in Geneva on Thursday, Dr Richard Harrop, said: "Our exploratory analyses of data from nine different trials of TroVax demonstrate significant associations between immune responses and overall survival in patients with colorectal cancer, renal cancer and prostate cancer.
"While it is essential that these observations are confirmed in large, randomised studies, collectively the data suggest that TroVax could provide some clinical benefit to cancer patients. In addition, the data show the vaccine is well tolerated by patients."
The vaccine is made up of a modified virus (Modified Vaccinia Ankara [MVA]), which acts as a vehicle to transport a second component, a gene that produces an antigen that is present in most solid tumours, called 5T4.
TroVax is injected into patients whose solid tumours have the 5T4 tumour antigen, so that the vaccine can trigger the body's natural immune responses to mobilise against 5T4.
"The virus acts as both a 'vehicle' to deliver the 5T4 antigen and as an 'adjuvant', which helps to ensure we stimulate a strong immune response to the 5T4 antigen," Dr Harrop said.
"Antibody and cellular responses can occur in response to both the viral vector (MVA) and to the 5T4 antigen.”
As part of the their study the researchers tested 180 patients for antibody responses to the vaccination, with 88 per cent showing a positive responses to 5T4 and 98 per cent showing positive responses to MVA.
Their study showed that the highest levels of antibody responses were detected after an average of two vaccinations for the MVA part of the vaccine and after four for 5T4.
Dr Harrop added: "When looking at the results from all the trials (colorectal, renal and prostate cancer patients), the magnitude of the 5T4-specific antibody response was associated with increased patient survival.
"Indeed, a doubling of the average number of antibodies in the patients between the first and third injections was associated with a reduction in the relative risk of death of 17 per cent. This effect was strongest in colorectal cancer patients.
"Both the magnitude and the frequency of immune responses elicited against our tumour target (5T4) are exceptionally high and could be considered 'best in class'. Since cancer vaccines rely on the induction of immune responses to be able to work, this is a very important attribute of TroVax."