The antibiotic drug rapamycin, which is currently being used for suppressing the immune system in patients having undergone a transplant and in treating some types of cancer, now has a potential new application: extending life. The finding was discovered by accident by researchers at Jackson Laboratory, the University of Michigan and the University of Texas Health Science Center working in parallel as part of a program sponsored by the National Institute of Aging to test possible anti-aging drugs more rigorously.

Specifically, the investigators found that mice fed rapamycin were not getting the proper dose in their bloodstream. They then reformulated the drug in the form of capsules, which slowly fed doses to the intestine. However, by that time the mice had already lived 600 days - the equivalent of 60 human years. Despite the advanced age of the animals, the researchers found that their life span increased by 14 percent in females and 9 percent in males. Says Lynne Cox, researcher in aging at the University of Oxford: "This is a very exciting study. It is especially interesting that the drug was effective even when given to older mice - equivalent to 60-year-old humans - as it would be much better to treat aeing in older people rather than using drugs long term through life."

The researchers are unsure why rapamycin produces its anti-aging effect - it may just halt tumor growth rather than delay the aging process in general - and they do not know what dose would be most effective. In addition, they warn that any drug that suppresses the immune system should not be used lightly, pointing out that the drug, which was originally identified in soil samples from Easter Island, is a powerful suppressor of the immune system. While it is commonly given to patients to help prevent the rejection of transplanted organs, its dangers to healthy people far outweigh any potential benefit.

The hope is that rapamycin's effects might highlight biological pathways involved in the aging process, which could then be targeted with a safer drug. Dr. Richard Miller of the University of Michigan emphasizes, however, that it will be at least 10 years before all the research is "sorted out." But he notes that "it's no longer irresponsible to say that following these up could lead to medicines that increase human life span by 10, 20 or 30 percent." And echoes Arlan Richardson, director of the Barshop Institute at the University of Texas: "I've been in aging research for 35 years and there have been many so-called ‘anti-aging' interventions over those years that were never successful. I never thought we would find an anti-aging pill for people in my lifetime; however, rapamycin shows a great deal of promise to do just that."

News Release: Antibiotic delayed aging in experiments with mice http://www.nytimes.com/2009/07/09/health/research/09aging.html?_r=1&ref=global-homeJuly 8, 2009

News Release: Rapamycin extends life in mice, raising hopes of life-prolonging drugs for humans http://www.timesonline.co.uk/tol/life_and_style/health/article6669805.ece July 9, 2009