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Salk scientists have been working since 2007 on a chemical compound, known as 516, that mimics the effects produced by exercise by triggering a specific genetic circuit, “a back door into the exercise genetic network,” Evans says.

The researchers built upon earlier work that identified a gene mechanism that encourages the muscles to burn fat, rather than carbohydrates, much as highly trained elite athletes do.

We are trying to take science out of the laboratory and bring it into the clinic in a way that can change people's lives. If we can do that, it would be a game-changer

“There are many reasons why people cannot run or walk or exercise,” Evans says. “If you can bring them a small molecule that can convey the benefits of training, you can really help a lot of people.”

Several other scientists are studying compounds that work differently from 516, but with the same aim: To give the benefits of exercise to people who aren’t able to do it.

Ali Tavassoli, a professor of chemical biology at Britain’s University of Southampton, has discovered a drug known as compound 14 that works “by fooling cells into thinking they have run out of energy,” Tavassoli says. It does this through a series of molecular actions that spur cells into metabolizing sugar, which produces energy, he says.

(Harvard cell biologist Bruce Spiegelman, who is working on an approach using exercise hormones, declined an interview, saying it wouldn’t be “wise” when “this area has been hyped so much.”)

Any such drug would require licensing by the Food and Drug Administration, yet the FDA doesn’t recognize “the inability to exercise” as an illness in need of a drug. So Evans has targeted 516 for young people with Duchenne muscular dystrophy, an approach that he believes offers the best chance for FDA approval. “This [disease] afflicts kids who can’t exercise and ultimately die of muscle wasting, often at a relatively early age, at 15 or 16,” Evans says. “It’s a disease with a large unmet medical need.”