Timeline: 3–5 Years
BACKGROUND: In 1997, geneticists Alexandra McPherron of the National Institutes of Health and Sie-Jin Lee of Johns Hopkins University discovered that “turning off” the protein myostatin can double the size of muscles in mice. Myostatin keeps muscle stem cells inactive during normal use. Turn off the protein’s signaling ability, and those cells turn their host into the Hulk. Last year, researchers at the Human Genome Research Center found the same mutation occurring naturally in a few Popeye-esque whippet dogs—typically a skin-and-bones breed—called bully whippets. In races, bully whippets run almost twice as fast as genetically normal whippets.
WHERE IT'S AT: As soon as McPherron and Lee announced their myostatin discovery, weightlifters were quick to offer their services as human test subjects. But a better test case came along by accident in 2000, after a German baby born without the protein exhibited extremely overdeveloped muscles. Today, though still extraordinarily muscular, the boy is in perfect health, suggesting that safely blocking myostatin in humans is a real possibility. In lab tests, two injections of one mysostatin blocker produced a permanent 50 percent muscle gain in mice. “Just about every major pharmaceutical company is developing a myostatin-blocking drug to treat muscle-wasting diseases like muscular dystrophy,” Lee says. Because these medicines will use traditional antibody-based drug-delivery methods, a myostatin inhibitor could be on the market in five years.
DETECTION: Myostatin blockers that use antibodies should be pretty easy to detect, since similar tests already exist. But alternative delivery systems like RNA interference and gene therapy, probably the norm for drugs in a decade, would make catching abusers near impossible. And although an athlete sporting a 50 percent increase in muscle mass might be a dead giveaway, partial inhibition of the myostatin pathway could lead to less obvious effects.
Left: A myostatin-deprived whippet runs twice as fast as a scrawny normal whippet [inset].