It's common knowledge that viruses make us sick. But a new, counterintuitive logic is coming into play in the war on cancer, namely, that viruses can also make us well.

So far, the results of various genetically engineered virus studies are tentative and are just beginning to progress into dozens of clinical trials. Results in some cases are quite encouraging for these oncolytic, or cancer-destroying, viruses. And some therapies could be ready for physicians' use in the next two or three years, said Frank McCormick, a cancer researcher at the University of California at San Francisco.

"The past two years have seen several major advances in oncolytic virotherapy," said David Kirn, the president of Jennerex Biotherapeutics Inc., a biotechnology firm in San Francisco, writing in the journal Gene Therapy. "A large number of clinical trials have been carried out. Safety in humans has been demonstrated in more than 800 patients."

There are at least six virus species that show promise for cancer therapy. One is a harmless strain that normally inhabits most people's lungs and gut. It's known as a reovirus, short for respiratory enteric orphaned virus. A genetically altered reovirus, manufactured as Reolysin by Oncolytics Biotech, a Canadian firm, has been shown to attack a variety of cancers.

In one clinical trial, 44 brain cancer patients were injected with Reolysin. Preliminary results are hopeful, according to research leader James Markert, a neurosurgeon at the University of Alabama at Birmingham. "We're very optimistic that viral therapy will be one of our weapons in the fight against cancer," he said. "It could be a major piece of the puzzle."

Other oncolytic viruses now in testing include:

-- A variation of the common herpes virus, which has passed initial tests for safety and effectiveness against brain tumors and melanoma. "Some patients had remarkable successes," Markert said.

-- Vaccinia, the first vaccine against smallpox, which was modified by Jennerex in San Francisco into an anti-cancer product called JX-594. In an initial trial, 14 terminal liver and lung cancer patients received injections of the JX-594 virus. They survived months longer than expected.

-- A genetically engineered cold virus, dubbed H101. The Chinese government approved it in 2005 for use against head and neck cancers. "This is the first oncolytic virus product approved by a governmental agency for human use," said Kirn.

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Source: http://www.mcclatchydc.com/homepage/story/41952.html

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