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Sure, mice on rapamycin may get some extra timeā€¦*

July 9, 2009 | 10:34 am

Even the hint -- from an animal study, no less -- that a specific drug may eventually help humans extend lifespan is enough to generate considerable popular excitement, presumably among those who have an interest in living longer. But if it's longevity you want, suppressing the immune system may not be the best way to go. That's what the drug in question, rapamycin, does.

For one thing, this suppression does tend to increase the risk of disease. An undesirable side effect by anyone's standards.

Rapamycin, an antibiotic commonly given to prevent rejection of organ transplants, was given to old mice in a recent study and, yes, the animals lived longer. Lifespan was increased up to 14% for female rodents (not to belabor the point, but it's worth repeating that the study was on, yes, rodents) and up to 9% for male rodents. *

Now, more on rapamycin.

The National Cancer Institute defines it as: "An antibiotic that blocks a protein involved in cell division and inhibits the growth and function of certain T cells of the immune system involved in the body's rejection of foreign tissues and organs. It is a type of immunosuppressant and a type of serine/threonine kinase inhibitor. Rapamycin is now called sirolimus." 

More on sirolimus from, which points out that the drug can increase the risk of certain types of cancer -- lymphoma and skin cancer, for example.

Here's a summary of the new research, published Wednesday in the journal Nature. It states: "Rapamycin may extend lifespan by postponing death from cancer, by retarding mechanisms of ageing, or both."

That's heady stuff. Here's a bit more context, in a more accessible version, from And a blog post from the site pointing out just where the word "mice" first appeared in various media reports.

As a Forbes story clarifies, the significance here is actually what the research tells us about the biology of aging. There's a long way to go between one finding about a signaling pathway in the body and practical effects in people. A very long way.

But, of course, that doesn't mean you shouldn't try to get this antibiotic and take it as an insurance policy. Mega doses, naturally, just to be on the safe side. 

-- Tami Dennis

* An earlier version of this story said the mice were all of the same type. Not so, as Mr. Miller (see comment below) was kind enough to point out.