GlaxoSmithKline's (NYSE:GSK) Requip is an effective new treatment for restless legs syndrome (RLS), a neurological condition characterized by uncomfortable sensations in the legs, and an uncontrollable urge to move the legs. Seinfeld fans can breathe a sigh of relief -- there's a treatment for Jimmy Legs!

RLS often afflicts people at night, disrupting sleep. Previously thought by many to be psychological, two new studies published this week have identified specific genes responsible for the syndrome. The studies were published in the prestigious journals New England Journal of Medicine and Nature Genetics. Both research groups identified the same gene variation, removing all doubt that RLS is a real disease.

In 2006 Requip sales came in at over $500 million. Not bad for a drug treating an "imaginary" disease! Think what it could sell with these studies, and if the medical community starts accepting RLS as a biologically based disorder. According to the FDA, RLS affects about 10% of the population. I'd bet those ad agencies are doing all nighters for the new campaign.

Boehringer Ingelheim's Mirapex is the other common treatment for RLS. Although sales data is hard to come by from this privately-held company, it is stepping up its marketing efforts. Mirapex has been the subject of a lawsuit, which claims that the drug caused compulsive pleasure-seeking behavior, particularly compulsive gambling. This sounds far-fetched, but the lawsuit does create negative publicity, at the very least.

Now that two well-regarded medical journals have presented important new data in RLS, I predict the disease will become more accepted by the medical community and patients will be looking for real treatment options. With a successful product already on the market, GlaxoSmithKline stands to benefit. And since Requip is already a $500 million drug, could blockbuster status and $1 billion in annual sales be far behind?

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Fool contributor Larry Rothman is happy to receive feedback, and promises to read it when not being wrestled by his three children. He doesn't have any positions in the companies mentioned.