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Experimental Cancer Vaccines Show Promise
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A new trial shows that a live Listeria vaccine called Lovaxin C is safe and even showed some benefit in 15 women with advanced cervical cancer.
Listeria is a common bacteria found on leafy vegetables and dairy products. "Most of us eat it routinely but don't know it, because it generates a strong immune reaction," study lead author John Rothman, vice president of clinical development at Advaxis Inc. of North Brunswick, N.J., which makes the vaccine, said at a Tuesday news conference. "It can cause disease, but it's safe, because the lowest doses of any number of antibiotics will clear it and will do it without impeding the immune response."
This vigorous immune response is what researchers are hoping will give the vaccine a fighting chance against cervical cancer. According to Rothman, there are at least 10 ways that Listeria attacks tumors, and probably more.
By study's end, only five patients still had progressive disease, seven were stable and one demonstrated a partial response to the vaccine. Three of the seven stable patients showed tumor reductions of about 20 percent and one of more than 30 percent.
The vaccine did cause flu-like symptoms in all patients (fever, chills, nausea), but those who had received lower-dose vaccines were treated easily with over-the-counter drugs, the researchers said.
Rothman's study was just one of several showing promise that were presented Tuesday at the American Association for Cancer Research annual meeting, in San Diego.
A second study, out of the Netherlands, found that the GVAX vaccine stimulated a significant immune response in men with prostate cancer. Five out of six participants receiving the highest dose of vaccine showed declines in PSA (prostate-specific antigen) levels of 50 percent or more.
"This appears to be a promising approach," study lead author Saskia Santegoets of VU University Medical Center in Amsterdam, said at the news conference.
Another vaccine — this one for prostate cancer that hasn't responded to other therapies — also showed hope. Three of six patients who received the highest dose of the vaccine saw declines in PSA levels of more than 50 percent. The trial involved 24 patients overall.
According to lead author Dr. Lawrence Fong of the University of California, San Francisco, the vaccine works by "educating" the immune system."
And, finally, antibody directed enzyme pro-drug therapy (ADEPT) showed positive responses in 44 percent of patients with either colorectal, gastro-esophageal, breast, gallbladder, peritoneal, appendix, pancreas or cancer of unknown primary site. With ADEPT, an enzyme activates a drug that has been targeted to the tumor by an antibody, at the site of the tumor.
SOURCES: April 15, 2008, teleconference with John Rothman, Ph.D., vice president of clinical development, Advaxis Inc., North Brunswick, N.J.: Saskia Santegoets, VU University Medical Center, Amsterdam, the Netherlands; Lawrence Fong, M.D., University of California, San Francisco; American Association for Cancer Research annual meeting, San Diego
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