Diabetes drug may help cancer patients

The next new treatment for breast, colon and prostate cancers, among others, may be a diabetes drug first approved in 1958.

Metformin, the most commonly used medicine to lower blood sugar, is the subject of about 50 cancer studies globally, U.S. government clinical trial information compiled by Bloomberg shows.

The research began after scientists found metformin prevented tumours in mice and diabetics were less likely to develop a malignancy if they were taking the five-cents-a-day pill than if they were on other diabetes medications.

The medicine is dispensed about 120 million times annually, according to a 2010 report in the journal Molecular Cancer Therapeutics. If the latest trials on breast and other tumours are successful, the drug could become a cheap weapon in the fight against a myriad diseases, including pancreatic and ovarian cancers. All told, cancer kills one in eight people and is the second-leading cause of death in most developed countries.

"The hope is that if it does show safety and efficacy, it would be available in a cost-effective way," said Chandini Portteus, vice-president of research, evaluation and scientific programs at Susan G. Komen for the Cure, a Dallas-based breast cancer advocacy group. "It would be wonderful for patients if we had something that we knew worked and was safe and low-cost."

The organization has spent about $10 million investigating using metformin on breast cancer, Portteus said. "We have to turn over every single rock to determine what the options are for patients who need them."

Metformin was the seventh-most-dispensed medicine in the U.S. in 2011, according to a list published by IMS Institute for Healthcare Informatics in April that ranked a group of painkillers. A pack of 84 500-milligram tablets of the diabetes pill, taken twice daily, costs Britain's National Health Service 1.37 pounds ($2.16), or about three pence (about five cents) a day.

The MD Anderson Cancer Center in Houston is studying metformin in at least eight trials.

"It is safe and it is cheap," said Donghui Li, an epidemiologist and professor at the centre. "It reduces the risk and has better survival" in studies she's done in pancreatic cancer patients.

Patients who took metformin had a 60 per cent lower risk of developing pancreatic cancer, according to a study Li published in 2009, in which she compared cancer patients taking metformin to people not on metformin. Metformin didn't benefit patients whose pancreatic cancer had already spread to other tissues, Li reported this year in the journal Clinical Cancer Research. Patients with malignancies confined to the pancreas survived longer if they were on metformin -- an average of four months longer, she found.

More research is needed to confirm those benefits as the disease is developing, Li said.

Further studies have been hampered by a lack of funding, Li said. Metformin lost patent protection years ago, meaning manufacturers no longer reap significant profits from its sale.

Pamela Goodwin, an oncologist at Toronto's Mount Sinai Hospital, is leading a trial in 3,582 breast-cancer patients at 300 locations. Data analysis from the five-year study may start in 2016 or 2017, Goodwin said. She was ready to start the research a decade ago, but lacked financial support from companies, she said.

"When they realized the results wouldn't be available until they lost their patent, they pulled out," said Goodwin, whose $25-million study is supported by the Canadian and U.S. governments and not-for-profit groups. Apotex Inc., a Toronto-based maker of generic medicines, is supplying metformin and a placebo used in the trial.

"All of the evidence has just become stronger while we waited," said Goodwin, who is also a professor of medicine at the University of Toronto.

Metformin is a synthetic form of a compound found in French lilac, used as an herbal remedy for frequent urination in the Middle Ages. Inside cells, it acts like a weak poison. Mitochondria, the power source in cells, are tricked into thinking the body is exercising and needs to draw more nutrients and energy from the blood, according to Dario Alessi, a biochemist at the University of Dundee.

Registering low energy levels, cells turn off the inappropriate division that is a hallmark of cancer, he said. By lowering blood-glucose levels and sensitizing cells to the effects of insulin, metformin may help control levels of the hormone, which is implicated in cell division and cancer.

-- Bloomberg News

Republished from the Winnipeg Free Press print edition October 6, 2012 A17