In this respect, vaccines are seen as the next up-and-coming cancer therapy, following a group of drugs that use proteins called monoclonal antibodies. Monoclonal-antibody drugs, six of which have made it to market, bind specifically to cancer cells and either slow down their growth or mark them for destruction by the immune system. But patients have to take the drugs continuously, and they’re expensive.With a vaccine, by contrast, patients would in theory only have to get a few shots; their own immune systems would do the rest. David Urdal, president and chief scientific officer of Dendreon, says cancer vaccines today are where monoclonal antibodies were ten years ago. “We’re now at that threshold with the cancer vaccine,” he says.
Some recent cancer vaccines have proved disappointing, however. A breast cancer vaccine from Biomira in Edmonton, Alberta, failed recently in advanced trials. And although a melanoma vaccine from Corixa of Seattle is approved in Canada, the FDA said approval in the U.S. would require a second trial, which Corixa may or may not attempt.
If other cancer vaccines work better, they might still pose problems. Vaccines could prime the immune system to go after not only cancer cells but also healthy ones. And some vaccine strategies require the isolation and purification of immune cells or tumor proteins from individual patients, which may make the treatments prohibitively expensive and labor intensive. But perhaps most worrisome is that, as vaccine developers well know, cancer cells are cunning creatures. “They have a lot of escape mechanisms to overcome obstacles generated by a vaccine,” said Steven Rosenberg, a researcher at the National Cancer Institute in Bethesda, MD, who is testing vaccines and other ways of recruiting the immune system to fight cancer.
And even proponents say cancer vaccines probably won’t be enough to fight cancer alone. Vaccines would have to work in combination with other therapies, bombarding tumors from all sides. Still, after decades of frustrated research efforts, recent advances are raising cautious hopes that these new therapies will soon take their place in the cancer-fighting arsenal.
CANCER VACCINE PIPELINE
|Company||Key to Vaccine||Status|
|Antigenics (New York, NY)||Proteins isolated from patient’s tumor||Kidney cancer vaccine late in phase III trials, with results expected next year; melanoma vaccine in early phase III trials|
|Whole tumor cells||Melanoma vaccine in phase III trials|
|Cell Genesys (South San Francisco, CA)||Genetically modified tumor cells||Prostate cancer, lung cancer, pancreatic cancer, and leukemia vaccines in phase III trials|
|Corixa (Seattle, WA), |
|Tumor protein or DNA||Lung and breast cancer vaccines in phase I trials|
|Dendreon (Seattle, WA)||Specialized immune cells from the patient activated outside |
|Prostate cancer trial late in phase III, with results expected next year|
|Progenics Pharmaceuticals |
|Carbohydrates and proteins found on tumors||Two melanoma trials: one in late phase III, the other in early phase III; prostate |
cancer vaccine in phase I