The day when doctors prescribe pills to combat aging may sound a long way off. But medical researchers are already starting to test such drugs in clinical trials—and encountering scientific and regulatory obstacles along the way.

Long wait: Proving that a medicine slows aging is a tough task for aspiring biotech companies. Credit: Catherine J. Jun/Detroit Free Press

Over the last few years, biologists have identified a slew of compounds that prolong the life of animal models such as yeast, worms and mice. On the basis of these results, they have formed a handful of companies around the world and are embarking on clinical trials in humans.

Showing that a drug prevents aging in people, however, is proving almost impossible. The obvious test is to give one group of people the drug, and another a placebo, and wait to see which lives longer. But this would take at least a decade, be enormously expensive and spell bankruptcy for a cash-strapped biotech firm. “No companies have money to last that long,” says David Sinclair at Harvard Medical School, Boston, whose studies on the antiaging compound in red wine called resveratrol led him to start Waltham, Massachusetts-based firm Sirtris Pharmaceuticals.

One way that Sinclair and other researchers plan to get around this problem is to show that a new drug delays or halts diseases associated with aging, without actually waiting for individuals to grow old. They hope to gain regulatory approval for slowing diabetes or arthritis, for example, and then carry out further trials to examine whether the drug also prevents these diseases from developing in the first place.

This approach is being taken at Elixir Pharmaceuticals, a company based in Cambridge, Massachusetts, that is planning human trials of molecules associated with aging in yeast and the worm Caenorhabitis elegans. The company is attempting to get drugs approved for market by showing that they prevent type 2 diabetes, says Bard Geesaman, Vice President of Medical Development.

Neither the US Food and Drug Administration (FDA) nor its equivalent, the European Medicines Agency, has ever approved a medicine specifically to combat aging. But if a company can convincingly demonstrate that a drug prevents a specific disease, officials say that it should be approved for that particular use. “Much of preventive medicine is, in a sense, antiaging medicine,” says David Orloff, an official in the FDA's Center for Drug Evaluation and Research.

But once such drugs hit the market, they raise the prospect that some people will use them as broad spectrum antiaging drugs even though their long-term side effects are unknown.

Indeed, some may already be swallowing prescription drugs, such as cholesterol-lowering statins and anticonvulsants, which have been shown to extend the life of animal models. “In the absence of human studies, it would not be advisable to take these medications to delay aging,” says Kerry Kornfeld, who studies such therapies at Washington University in St. Louis, Missouri.

Those in the field believe it will be decades before a drug is approved specifically for combating aging. In order to do so, researchers will probably need to find genes or other biological molecules whose levels vary with a person's age and show that the drug stops this change. Until such trials are completed, it is irresponsible to label a drug 'antiaging', says Leonard Hayflick who studies gerontology at the University of California, San Francisco.