Could sirolimus turn out to be the elixir of life?

The immunosuppressant drug sirolimus (rapamycin) has been found to extend the lifespan of middle-aged mice by around a third, giving rise to hopes that it could also prolong life in humans.

When mice aged 20 months old, equivalent to 60 years of age in humans, were given sirolimus in a study reported in Nature, their life expectancy increased by 28–38 per cent. In human terms, this would be greater than the predicted increase in life expectancy if cancer and heart disease were eradicated.

“We believe this is the first convincing evidence that the ageing process can be slowed and lifespan can be extended by a drug therapy starting at an advanced age,” says Randy Strong, director of the National Institute on Aging Interventions Testing Center.

Research has thus far only identified two life-extending interventions in mammals: calorie restriction and genetic manipulation. The mode of action of sirolimus appears to be a partial shutdown of the same molecular pathway as reducing food intake.

It does so through a cellular protein called mTOR (mammalian target of rapamycin), which controls many metabolic processes and responses to stress.