of any sign of cancer. The researchers, from the Royal Free Hospital, University College Medical School, and the Gray Laboratory Cancer Research Trust now plan to carry out trials in humans. The new drug, Combretastatin (CA4P), is derived from the bark of an African bush willow. It works by destroying the blood vessels that supply the tumors with vital nutrients. However, it has no damaging effect on healthy tissue. The destruction of the tumors is completed by attacking them with radiation carried into the cells by antibodies similar to those used by the body's immune system to destroy infection. Essentially, the Dr.ug attacks the tumor from the inside out, while the radiotherapy attacks from the outside in. In isolation, each treatment could never completely destroy all the cancer cells. But in tandem they are a potent force, which the scientists believe can produce a longterm cure. Professor Richard Begent, head of oncology at the Royal Free Hospital, led the research. Even killing off a tumor's blood supply was not enough to destroy it because
part of it was still sustained by the body's normal blood supply. However, the radioactive antibodies used in the new treatment were able to starve the tumor of this supply too. He said, "This does not necessarily mean that we would be able to cure people, but it does make it worth exploring this further and seeing if it can be of benefit to people with cancer." Dr. Lesley Walker, the Cancer Research Campaign's Director of Cancer Information, said, "This is the latest step in the very encouraging development of this Dr.ug for treating cancer. This good news confirms what we have been saying all along — that treatments that directly target cancers and spare normal tissue will be the cancer therapies of the future." Dr. Walker said that as well as proving to be an effective treatment, the combination therapy should also greatly reduce side effects for the patient. Approximately 200 patients with a variety of different cancers will be recruited to take part in the human trials. A drug that indirectly attacks tumors by destroying the blood vessels that feed them substantially boosts the effectiveness of traditional anti-cancer medications in laboratory animals, new University of Florida research shows. Scientists have also found that by combining CA4P prodrug with standard chemotherapy agents, tumor cells in mice were killed off at 10 to 500 times the rate of chemotherapy alone.
The drug was employed against human tumor cells breast, ovarian and AIDS-related Kaposi's sarcoma that had been injected into the animals. "We previously had shown that the drug was effective when combined with radiation therapy," said Dietmar Siemann, a professor of radiation oncology in UF's College of Medicine. "But now we have shown that it performs well with traditional anti-cancer drugs. It does well on its own, but it's also a way to enhance the effectiveness of chemotherapy." In breast and ovarian tumors models, combretastatin with cisplatin or cyclophosphamide caused a dramatic increase in tumor cell death a 10- to 500-fold increase -- over any of the medications by themselves. Combretastatin by itself does not eradicate an entire tumor because it attacks only new blood vessels that have developed to support the cluster of cancerous cells. The outer rim survives because it is nourished by blood vessels that supply normal tissue. An associate professor of radiation oncology at the Stanford University School of Medicine,
Amato Giaccia, noted that several laboratories around the world are finding similar results with combretastatin and a variety of tumor types. That's encouraging, he said, because "it's getting real and reproducible effects."
