Monday May 4, 1:55 pm Eastern Time
US doctors warn against euphoria over cancer drugs
By Maggie Fox, Health and Science Correspondent
WASHINGTON, May 4 (Reuters) - Doctors said on Monday they were excited about a new way to attack cancer but warned against premature euphoria over drugs that may not work in people.
The two drugs, angiostatin and endostatin, have completely wiped out tumors in mice. A feature story about the work published in the New York Times on Sunday sent stock in EntreMed Inc. (ENMD - news), which has rights to the drugs, soaring. Shares in Bristol-Myers Squibb Co. (BMY - news), which has an agreement with EntreMed, also shot up in the morning.
''The data are very impressive and compelling. But it is still mouse data. We need clinical data in humans before we can anoint them as miracle drugs,'' said Dr. Jim Pluda, an oncologist at the National Cancer Institute (NCI) who is overseeing research in this area.
''There have been a number of compounds in the past that have cured mice and did not translate into efficacy in human clinical trials. The field of oncology is littered with the bodies of agents that were the next cure for cancer.''
Nonetheless the NCI is very excited about the drugs and has made their development a top priority. The drugs work to stop the growth of blood vessels that tumors need to grow and flourish. This process of growing arteries is called angiogenesis, so the drugs are known as angiogenesis inhibitors, or anti-angiogenesis drugs.
Pluda compared the approach to trying to eliminate dandelions from a lawn.
''Normally we keep whacking off the top and the dandelion keeps growing back,'' he said in a telephone interview. ''But if you kill the roots of the dandelion, the whole plant dies. We are killing the mechanism by which the tumor cells get nutrition.
In addition, there are few side-effects, unlike the standard treatments that use toxic drugs or X-rays.
''The hope is that you kill more cancer than normal cells and that the normal cells then recover first,'' Pluda said. ''But the cancer cells eventually acquire resistance to these agents while the normal cells don't.''
With angiogenesis inhibitors, there is no resistance because the tumor is not being directly attacked.
''The remarkable thing about these new agents is the lack of resistance. You could give the drug over and over again and the tumor continues to respond,'' Pluda said.
Plus they are naturally occurring agents. ''Angiostatin is actually a portion of a normal circulating blood product called plasminogen. Endostatin is a small fragment of a type of collagen called collagen 18 that is normally found in the body but localized around blood vessel cells,'' Pluda said.
The NCI is very excited about this approach, which was first reported in the science journal Nature in November 1997. It was developed by Dr. Judah Folkman, of Children's Hospital and Harvard Medical School in Boston, Massachusetts.
''We owe Dr. Folkman an enormous debt of gratitude because he initiated the field, he kept the field alive when he was being assailed by the slings and arrows of naysayers,'' Pluda said.
But even Folkman remains cautious.
''If you have cancer and you are a mouse, we can take care of you,'' he told the New York Times. And he said it could be years before the drugs are ready to be tested in humans.
The drugs may not be suitable for use in children or pregnant women. Angiogenesis is very important for the growth of unborn babies and children. ''That is an issue,'' Pluda said.
But even if this approach does not work, there are also hopeful approaches being worked on with vaccines, with gene therapy and with another form of therapy on the genetic level known as antisense therapy.
Several other companies are also working on other formulations of angiogenesis inhibitors. |
