AMSTERDAM, Netherlands (AP) -- Eagerly awaited test results on a much-publicized new cancer drug designed to stop tumors by cutting off their blood supply indicate the medication is safe and show promising signs it may help control the disease.
However, the results released Thursday suggest the drug endostatin is unlikely to be the kind of across-the-board cancer cure that many had hoped for.
The drug was tested on terminally ill cancer patients largely to assess its safety.
No dramatic recoveries have so far been seen among the 61 patients studied.
"Some patients benefited, but many did not," said one of the chief investigators, Dr. Roy Herbst, an assistant professor of medicine at the M.D. Anderson Cancer Center in Houston. "These patients were very sick. Most of their tumors are going to grow no matter what you do."
The best results were seen in a 50-year-old man with cancer in his jaw. His tumor shrank by 62 percent in eight weeks.
A tumor in the pancreas of another patient shrank by 19 percent after he had been taking the drug for a year.
In five other cases, the disease remained stable, with the tumor neither progressing nor shrinking.
Despite the lack of cures, the testing provided some evidence the drug may cut off a tumor's blood supply, as intended, offering hope the approach could work better in patients who are less desperately ill.
Blood flow through the tumors became less robust and chemicals involved in blood vessel creation diminished as patients were given increasingly higher doses of endostatin.
No serious side effects were noticed in any of the patients, the scientists said.
While some experts considered the test results "tremendously promising," others were cautiously optimistic.
The recent discovery that angiogenesis, or the creation of new blood vessels, is vital to a tumor's survival has been the basis for the hottest area in cancer research.
Drugs that attack the process are called angiogenesis inhibitors. Endostatin is one of dozens of such drugs, which are at varying stages of development and attack blood vessel growth from different angles.
"Many of them have shown little toxicity, and this is not the first to show a response," said William Li, head of the Boston-based Angiogenesis Foundation, a nonprofit information clearinghouse that tracks research in the field.
"But it's unprecedented at this stage of testing to have such a comprehensive measurement of markers that indicate there might be a benefit," he added.
Tracking the indirect indicators has allowed scientists to see more promising signs earlier in the research than normal, Li said.
Besides M.D. Anderson, the Dana-Farber Cancer Center in Boston and the University of Wisconsin Comprehensive Cancer Center in Madison conducted the studies.
The Boston study was sponsored by the drug's maker, EntreMed of Rockville, Maryland, while the other two were funded by the U.S. National Cancer Institute.
Some experts predict endostatin and the other drugs will in most cases halt cancer growth, turning the disease from an acute fatal illness into a low-level ongoing condition, like diabetes or arthritis.
In other cases, the cancer may be wiped out completely, while in still others, the drugs may need to be used in combination with chemotherapy and radiation. On some cancers, the drug may not work at all.
"No one piece of information by itself is that strong, but the entire picture is something that deserves further study," Herbst said.
Endostatin came to wide public attention two years ago when an optimistically worded New York Times article set off a frenzy of anticipation about the drug, which then was still in animal testing.