Scientists could be closer to an anti-ageing pill that really works. Rapamycin, now used as an immunosuppressive in organ transplant, is a key ingredient. It is also used in heart operations and is being tested for its anti-cancer properties.
Rapamycin was first found in the 1970s in the soil of Easter Island - one of the most remote and mysterious places on the planet. The chemical is produced by a microbe that lives in the soil.
In tests, it increased the life expectancy of animals by a staggering 38 per cent.
In its current form, the drug is too dangerous to hand out as an anti-ageing pill. As it suppresses the immune system, it also makes people vulnerable to any viruses and bacteria.
But a safer drug for treatment of ageing in humans could be developed within a decade, it is now fondly hoped, Daily Mail reported.
Dr Arlan Richardson, who led the research at the University of Texas, said: 'I've been in ageing research for 35 years and there have been many so-called "anti-ageing" interventions over those years that were never successful.
'I never thought we would find an anti-ageing pill for people in my lifetime. However, rapamycin shows a great deal of promise to do just that.'
In the study, reported in the journal Nature, scientists tested rapamycin on nearly 2,000 laboratory mice aged around 600 days old - roughly the equivalent to a 60 -year-old person.
Around a quarter of the mice were given a normal diet, the others were given the Easter Island chemical.
The drug increased the maximum life span of the mice from 1,094 days to 1,245 days for females, and from 1, 078 to 1,179 days for males.
From the point the mice began the treatment, the drug extended the females' life expectancy by 38 per cent, and males by 28 per cent. Overall it expanded their life span by 9 to 14 per cent.
What amazed the scientists is that the mice only started to get the drug in middle and old age.
Dr Randy Strong, the director of the Ageing Interventions Testing Centre in San Antonio, who took part in the study, said: 'We believe this is the first convincing evidence that the ageing process can be slowed and life span can be extended by a drug therapy starting at an advanced age.'
He added: 'This study has clearly identified a potential therapeutic target for the development of drugs aimed at preventing age-related diseases and extending healthy life span.'
Until now, scientists have developed just two ways of extending the life span of mammals.
One is to tinker with their genes, the other to restrict their diet. Repeated studies have shown that cutting down on calories can make animals and people live longer.
They believe rapamycin - which acts on a protein in cells called TOR - may fool the body into thinking that calories are being restricted.
British scientists described the findings as exciting - but warned that rapamycin is too dangerous to give to people.
Because it weakens the immune system, it exposes people to potentially dangerous diseases and could even increase the risk of cancer.
In its current form, an extended life span would come at the cost of having to live a Howard Hughes like existence in a germ free tent.
Researchers want to find another more subtle drug target that extends life, but which doesn't damage the immune system.
Dr Lynne Cox, researcher in ageing at Oxford University, said: 'This is a very exciting study where a single drug with a known cellular effect increases the life expectancy and life span of mice. 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 ageing in older people rather than using drugs long term through life.
'In no way should anyone consider using this particular drug to try to extend their own life span as rapamycin suppresses immunity. While the lab mice were protected from infection, that's simply impossible in the human population.
'What the study does is to highlight an important molecular pathway that new, more specific drugs might be designed to work on.
'Whether it's a sensible thing to try to increase life span this way is another matter: Perhaps increasing health span rather than overall life span might be a better goal.'