Researchers say they can measure new cancer drug Canadian Press Updated: Tue. Jan. 18 2005 9:43 AM ET TORONTO — An international team of researchers led by some Toronto scientists has found a way to measure the effects of a new class of cancer drugs that are believed to hold great promise. The scientists believe their finding could hold a key to the future success of this form of therapy, known as anti-angiogenesis. A spokesperson for the Canadian Cancer Society said the test, led by Dr. Bob Kerbel at Sunnybrook and Women's College Health Sciences Centre, hasn't yet been proven to work in humans and isn't likely to be available on an individual basis any time soon. "Those caveats not withstanding . . . what Bob has shown as I understand it is a very exciting proof of principle that in fact you can' monitor and you can measure anti-angiogenesis therapies and treatments using something that could be developed into a fairly simple or at least straightforward blood test," said Michael Wosnick, executive director of the cancer society's research arm, the National Cancer Institute of Canada. The cancer society helps fund Kerbel's work. "I have a lot of hope for anti-angiogenesis for a really, really important mainline treatment for all kinds of cancers," Wosnick added. Angiogenesis is the term for the development of blood vessels to feed tissues - or in the case of cancer, tumours. The idea that you could starve a tumour by turning off its blood supply - anti-angiogenesis - was first advanced in the early 1970s by Harvard-based cancer researcher Judah Folkman. It's a theory that has experienced a roller-coaster ride of reaction from the scientific community, which has ridiculed and embraced it by turn, Kerbel said in an interview Monday. Some anti-angiogenic drugs have shown great promise in mice, but the results in humans have disappointed. Kerbel said one of the main problems is there has been no way to measure the effect of the drugs, meaning its has been impossible to determine the optimal dose. With traditional cancer therapies, dosing has followed a brutal regime that involves subjecting patients to the highest dose they can tolerate, followed by recovery intervals. There is some suggestion that with anti-angiogenic drugs less might be more. But until researchers can measure how the drugs are doing, there'd be no way to effectively tell. Kerbel's team has found what scientists call a biological marker that they believe solves the conundrum. They found that measuring levels of endothelial cells and endothelial progenitor cells circulating in the blood stream can be a good indicator of whether a therapy is inhibiting angiogenesis. These types of cells are believed to originate in the bone marrow and are known to play a key role in the development of blood vessels. "We can actually say that we have a way to measure the angiogenic activity. And if we have a way to measure angiogenic activity, we have a way to measure anti-angiogenic activity," said first author Yuval Shaked, a post-doctoral fellow working with Kerbel. The findings could be an immeasurable help to drug companies previously stymied in efforts to set appropriate doses for their therapies or prove to regulators that they work. "It's huge for them," Kerbel said. "Because they are investing enormous amounts of money into these sorts of drugs. Sometimes hundreds of millions of dollars. "And at the end of the day, everything they've done has failed, not because they don't have an active drug . . . but because they weren't able to assess it properly."© Copyright 2004 Bell Globemedia Inc.
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