Testing Shark Cartilage as a Cancer Drug
More than a decade after shark cartilage was first touted as a potential cure for cancer, researchers still do not know whether cartilage has something to offer cancer patients. The best hope for finding out may be a lung cancer study that's testing a drug made from a concentrated extract of shark cartilage.
The drug, AE-941 (Neovastat), was developed by the pharmaceutical company Aeterna Zentaris of Quebec City. Unlike shark products in health food stores and on the Internet, it's been through the same development process as other pharmaceutical drugs and is available only through the trial.
"This is an interesting natural product," says Dr. Scott Saxman of the Cancer Therapy Evaluation Program at NCI, which is collaborating with other NCI programs to sponsor the trial. Studies of the drug in mice suggested that it impairs blood vessel growth, or angiogenesis, through various mechanisms.
Long before shark cartilage became a folk remedy, researchers were investigating cartilage in efforts to develop cancer drugs that kill tumors by inhibiting the blood vessels that supply them with nutrients. Cartilage lacks blood vessels and can prevent their growth.
The research has been done mainly with shark cartilage, as opposed to another type, not because sharks are resistant to cancer (they do get cancer), but because they are a reliable source of the material. Their skeletons are made almost entirely of cartilage.
"This trial has nothing to do with a belief that sharks are somehow magical creatures," says Dr. Charles Lu, of the University of Texas M.D. Anderson Cancer Center, who leads the AE-941 study. "We want to know whether a cartilage product developed as a pharmaceutical and tested in a scientifically rigorous manner is effective against cancer."
In the trial, patients with non-small-cell lung cancer will either receive AE-941 or a placebo while undergoing chemotherapy and radiation treatments. About 360 patients out of a planned 750 are enrolled, and there are no results yet.
The trial is funded by NCI and the National Center for Complementary and Alternative Medicine. (In an unrelated trial, patients with advanced kidney cancer did not benefit from AE-941.)
No one knows how many cancer patients consume shark products, but surveys in the late 1990s reported that more than 25 percent of some patient populations used them as complementary or alternative medicine (CAM).
Around that time, NCI decided to evaluate two very different products: AE-941, which had science behind it but was not in use; and Benefin, a powder extract already used by patients.
"The combination of the two trials was intended to provide a better picture of products that have rarely been scientifically evaluated," says Dr. Jeffrey White, director of NCI's Office of Cancer Complementary and Alternative Medicine.
The Benefin trial recently closed early because enrollment was low and preliminary results were discouraging. "We didn't see any evidence of a benefit, and the extract wasn't well tolerated," says Dr. Charles Loprinzi, of the Mayo Clinic, who led the trial.
Reporting their findings in the July 1 Cancer, the researchers say that well-designed trials of other cartilage substances, such as AE-941, may well succeed. Dr. Loprinzi, who has evaluated a dozen CAM agents derived from natural products, views cartilage as just another source of potential anticancer agents.
The process of creating AE-941 - by purifying a substance to concentrate biologically active molecules - is basically what cancer researchers have done for years, notes Dr. Andrew Vickers, of Memorial Sloan-Kettering Cancer Center, who has written about CAM products.
"The lesson is that to develop agents for cancer you need to be very careful about it," Dr. Vickers says. "You can't just make global claims like, 'shark cartilage cures cancer.'"
False claims about sharks rarely getting cancer and exaggerated reports of Cuban cancer patients benefiting from shark cartilage ignited the fad in the early 1990s. It persists, says Dr. Vickers, because patients who are not doing well will always want to try something else, and these products are widely available in stores and on the Web.
"People do take over-the-counter natural products," says Dr. Saxman. "And there's evidence that some of these products can enhance or interfere with other medications, so patients need to inform their doctors and discuss whether they should be taking them."
According to Aeterna Zentaris, no sharks are killed to manufacture AE-941; the cartilage comes from the remains of sharks slaughtered for meat. Nonetheless, in the last 15 years, global shark populations have declined significantly, and researchers attribute this to overfishing and rising consumer demand for shark products.
Of course, if AE-941 proves useful against cancer, researchers could try to create a synthetic version, removing sharks from the process entirely.
SOURCE: National Cancer Institute Cancer Bulletin, July 26, 2005
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