Rapamycin was originally found underneath an Easter Island moai. Andrzej Gibasiewicz/Shutterstock Right now, a naturally-produced substance called rapamycin is being described as the source of potentially one of the most transformative medicines in the world, one that has a small but not impossible chance to become the first drug to successfully slow the effects of aging — "the ultimate preventative medicine," as Matt Kaeberlein, a prominent researcher who studies aging at the University of Washington, described it to Bloomberg Businessweek.

But — as told in a wide-ranging Bloomberg Businessweek cover story — the only known samples of it would have been destroyed if it weren't for a researcher who was just too intrigued by rapamycin's potential to let that happen.

This substance, produced by a bacteria, has already been used to develop treatments for kidney, lung, and breast cancers (Novartis earned more than $1 billion from these treatments in 2013), among many other uses. Yet it wouldn't — couldn't — be the subject of such excited pronouncements, if Dr. Suren Sehgal had obeyed his bosses at Ayerst Laboratories.

In 1983, Ayerst was closing their Montreal lab and decided that everything that didn't have a defined productive use yet should be destroyed.

Almost a decade before that, Sehgal had found a rare bacteria in some dirt a 1964 Canadian research team had scraped from underneath a moai, one of the massive stone heads on Easter Island. Sehgal discovered that the bacteria, Streptomyces hygroscopicus, produced a powerful anti-fungal compound. He sent a sample to the National Cancer Institute, which has a branch dedicated towards investigating the potentially powerful biological agents derived from the natural world.

Sehgal gave the compound the moniker rapamycin, reminiscent of the native name for the island it came from, Rapa Nui.

But Ayerst didn't want to pursue the rapamycin investigation. Sehgal kept experimenting with it on the side — he once used it to create an ointment that cured a fungal skin infection for a neighbor. "It was probably illegal," his son Ajai Sehgal tells Bloomberg Businessweek, but it worked.

Yet it fell onto the list of "nonviable" compounds that were slated for destruction when Ayerst shuttered their Montreal operation.

And even though Sehgal was a dedicated employee (one of the only ones to keep his job after they closed the lab), he couldn't bear destroying this thing he was so excited about.

So he took a rogue step. Instead of destroying the rapamycin, he took a few glass vials of the bacteria home and stashed them in his freezer. As Bloomberg Businessweek reports, he wrapped them in plastic and stuck them beside some ice cream, writing a note that said "DON'T EAT!"

Don't eat, indeed.

He and his family moved to Princeton, N.J., to continue working for Ayerst in their lab there.

In 1987, Ayerst was bought by another pharmaceutical company, Wyeth — and they were amenable to letting Sehgal continue his research.

When Sehgal discovered that rapamycin also suppressed the immune system, he and Wyeth realized it would help people receiving an organ transplant, by making their bodies less likely to reject it. That usage was approved by the FDA in 1999.

But the other thing that's making waves right now is the idea that rapamycin could actually be the source of an anti-aging pill that could change the basic course of human lives.

Unfortunately, this isn't proven to work at all, and it'll be a long time before it could be. In theory, a drug like that would need to be taken by healthy people, probably every day for years, with essentially no side effects. That's incredibly tough to demonstrate the safety and efficacy of, especially on a large scale.

But the reason some researchers think it's possible is the way that rapamycin works on a cellular level. It affects a pathway that helps regulate growth. That pathway can be switched into a more conservative mode where it grows less and consumes less — lack of nutrients seems to trigger the same effect, which may be why fasting helps people live longer. It seems that rapamycin can do the same thing in cells, though this has not yet been demonstrated in humans.

A study by the NIH, for example, shows that feeding mice rapamycin can extend their lives, though again, many things that have been shown to work in mice never work in humans.

Another big concern is immunosuppression. If rapamycin suppresses the immune system of an elderly person, even as it helps slow their cellular aging process, that may be too much of a negative side effect.

Because of this potentially huge limitation, Novartis is actively trying to find a rapamycin derivative that is not an immunosuppressant. A recent company-funded study showed that one particular derivative seemed to improve the immune response of a group of elderly people in response to a flu shot. While a flu shot is not the same as a real infection and further testing is needed, it's an exciting development for Novartis, suggesting there may be a way around some of rapamycin's potential pitfalls.

Still, until there is much more evidence about rapamycin's safety and efficacy, it's worth remembering that when it comes to medicines that can actually extend the life of a healthy person, "the batting average is zero," S. Jay Olshansky, a professor of public health at the University of Illinois, tells Bloomberg Businessweek.

Sadly, Sehgal himself never got to see how far the excitement about his discovery has come. As his son writes, he died in 2003, five years after a diagnosis of stage 4 metastatic colon cancer.

Read the full story of rapamycin at Bloomberg Businessweek.