Scientists are testing the drug rapamycin, an anti-rejection drug for kidney transplant patients, to see if it will help extend the lives of large dogs and possibly protect humans against old-age diseases such as cancer or heart disease, The Guardian reported.

When given to mice, the drug has been shown to increase the length of their lives by more than 10 percent. “If you give rapamycin to 20-month-old mice — when they are in their equivalent of middle age — you can see pretty profound benefits in terms of rejuvenating their bodies and increasing their lifespans,” said Dr. Matt Kaeberlein, of the University of Washington. “That is why we are so excited about the drug.”

This discovery led scientists to start trials in humans and other species of mammals, particularly large dogs which tend to have shorter life expectancies than their smaller counterparts.

“The crucial point is that at that age, a mouse is the equivalent age of a nine-year-old dog. So if we now start giving the drug to middle-aged dogs, we have a chance of finding out in only a few years that it works on larger animals,” said Kaeberlein. “The equivalent age for humans is 60. However, it will take much longer to obtain results from humans to see if the drug is working or not.”

Part of the appeal of using dogs in the trials is that they are exposed to the same environmental influences as their human owners. Acknowledging that these tests are currently aimed at helping dogs, Kaeberlein says that the study could help justify future studies on humans.

A successful animal trial would “show that rapamycin could be added to pet food in order to extend the lives of household dogs. In addition, it would provide support for pressing ahead with trials of rapamycin on human volunteers … [and] provide key data on dosage and other parameters when designing trials” for humans, the Guardian said.

Kaeberlein says he and the other scientists working the trials are looking for “mid-to-large dogs” because they “tend to have lifespans of 11 to 12 years and also tend to get heart disease and cancer. These are the conditions that rapamycin appears to be able to help ward off, so that makes them better subjects for our proposed trials.”

Kaeberlein also stresses that what he and his colleagues are not doing “laboratory” trials — “We are not going to do anything to the dogs once we have finished. We are just asking owners to cooperate with us to see if this drug, added to their pets’ diets, extends their lives significantly from middle age into senility.”

The scientists are hopeful that the tests, which should begin some time next year, will lead to a larger study using a larger sample of dogs in the next few years. “That should be the one that really shows whether or not this drug will lengthen life – for dogs and possibly humans,” Kaeberlein said.