MONDAY, Aug. 2 (HealthDay News) -- Scientists have genetically tweaked a virus to fashion a therapeutic vaccine that appears to attack a variety of advanced cancers.
The vaccine has provoked the required tumor-fighting immune response in early human trials, but only in a minority of patients tested.
And one expert urged caution. "They were able to generate an immune response [with the vaccine]. That's a good thing but we need a little more information," said Dr. Adam Cohen, assistant professor in medical oncology at Fox Chase Cancer Center in Philadelphia. He was not involved in the study.
"This is the first study in cancer patients with this type of vaccine, with a relatively small number of patients treated so far," Cohen noted. "So while the immune response data are promising, further study in a larger number of patients will be required to assess the clinical benefit of the vaccine."
One vaccine to treat prostate cancer, Provenge, was recently approved by the U.S. Food and Drug Administration. However, Cohen noted that many other cancer vaccines have shown early promise and not panned out.
The theory behind therapeutic cancer vaccines is that people with cancer tend to have defects in their immune system that compromise their ability to respond to malignancy, explained study lead author Dr. Michael Morse, associate professor of medicine at Duke University Medical Center.
"A vaccine has to work by activating immune cells that are capable of killing tumors and those immune cells have to survive long enough [to] get to the tumor and destroy it," he explained.
For this vaccine, the authors used the Venezuelan equine encephalitis virus, an "alphavirus" that affects the nervous systems of equines, including horses and donkeys.
Alphaviruses provide an attractive vector for vaccines because they naturally seek out dendritic cells, which stimu
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