FRIDAY, April 6, 2012 (Health.com) — Each year billions of dollars are spent in the search to find new cancer drugs. Very few of these would-be treatments end up being approved by the government and entering widespread use, which makes it all the more intriguing that one of the most promising new cancer drugs in years is, in fact, an old drug.
Metformin, a diabetes drug, was approved by the Food and Drug Administration in 1995, and since then tens of millions of Americans with diabetes have taken it daily to control their blood sugar. The first hint that metformin might also have anticancer properties came a decade later, when two research teams separately reported that diabetes patients were less likely to develop cancer, and less likely to die from the disease, if they were taking the drug.
This news wasn’t entirely surprising: Metformin treats diabetes in part by lowering insulin levels, and several types of cancer—such as those of the breast, colon, and prostate—have been linked to high levels of that hormone. But then, in 2006, researchers in Canada working with breast-cancer cells found that metformin increased the activity of an enzyme involved in tumor suppression, suggesting that the drug might fight cancer by working directly on cancer cells.
These two developments “set off a minor firestorm of interest,” says Pamela Goodwin, M.D., a breast cancer researcher at the University of Toronto. “Basically there’s been a convergence of all this information, and even before it was available we could see there was a strong signal here.”
Over the past several years, studies in cell cultures and animals have found that metformin appears to slow or stop the growth of a wide range of cancer cells, including those associated with breast, prostate, lung, and endometrial cancer. And the pace of research has picked up. This week, at the annual meeting of the American Association for Cancer Research (AACR) in Chicago, researchers presented preliminary results from no fewer than 20 studies on metformin, including some in humans.
“I think certainly over the last two or three years that metformin has come to the fore, and people recognize that it has an important role to play,” said Anthony Joshua, M.B.B.S., a staff medical oncologist at Princess Margaret Hospital, in Toronto, who presented new research at the meeting.
The promising study findings aren’t the only cause for enthusiasm among doctors. Metformin’s decades-long history as a diabetes drug—it entered the U.K. market back in 1958—suggests that it’s generally safe. It’s also extremely cheap. The U.S. patent on metformin expired in 2002, so the drug is now available in various generic versions that cost just pennies per pill.
Extensive placebo-controlled clinical trials will be needed before metformin can be used as a standard cancer treatment. While it’s too soon to say how that research will play out, metformin’s apparent versatility and low cost seems to offer unusual potential, says Michael Pollak, M.D., director of cancer prevention at McGill University, in Montreal.
“This is not a cancer drug development story like any other,” says Pollak, who led the 2006 study on metformin and enzymes. “It contrasts so much with what you hear in cancer research: doctors developing new targeted therapy that costs $800 a month, and it works a little bit—but only for certain kinds of patients with certain kinds of tumors. We don’t very often see [that] the generic drug that’s available at your drugstore anyways might have some use for cancer.”
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