Some docs not so hot on potential for diet drugs Qsymia, Belviq

There is a lot of investor excitement around the two new diet drugs, Qsymia and Belviq, given the obesity problems in this country and the hope by many overweight people that they can take a pill to solve their problem. But is there excitement among the doctors that have to prescribe those drugs? For some, not so much.

"I understand the desire for a miracle pill, a silver bullet, to deal with the very difficult and stubborn problem of obesity--but I don't think it's going to be that easy," Dr. Lee Green, professor and chair of family medicine at the University of Alberta in Canada, tells ABC News. He predicts that neither drug will be on the market in 5 years.

Investors certainly have large expectations for the two drugs, Qsymia (formerly Qnexa) from Vivus ($VVUS), which the FDA approved this week, and Belviq from Arena Pharmaceuticals ($ARNA), which was approved a couple of weeks ago. The market for weight loss drugs is enormous, estimated at $60 billion a year, and analysts have already predicted $1 billion in sales for Belviq in a few years and $1.2 billion for Qsymia by 2016.

Of course diet drugs have had very mixed performance in the past. Patients sometimes can't tolerate the side effects and others quit using them if they don't turn out significant results. And therein lies the problem in the eyes of some doctors, ABC reports. In their trials, patients taking Belviq lost about 5% of their total weight, while for Qsymia users, it was about 10%.

"Up to 10% weight loss' sounds great, until you look closely," Green says. "That's when used by selected volunteer patients in carefully designed, closely monitored clinical trials. We'll be lucky to get half that in the real world."

Not all doctors are so pessimistic. Dr. Albert Levy, assistant professor of medicine at the Mount Sinai School of Medicine, tells ABC that when data from clinical trials showed benefits, he started giving patients the same combination of drugs in an off-label use. And it worked, he says. "Once the patient has learned how to control the appetite and has lost a good amount of weight, she or he is stimulated to continue to lose weight without the medications," Levy says.

The doctors all agreed that the drugs can only start patients down the weight-loss path and that they have to make lifestyle changes, eat better and exercise as part of a lifelong journey.

While the market is big, there are some limits on the market as well. Medicare, for instance, explicitly does not cover weight-loss drugs and only 10 state Medicaid programs specifically do.

There are other potential problems as well, as illustrated Friday when a short seller, Citron Research, posted a report on its website about the threat of Johnson & Johnson ($JNJ) challenging patents to Vivus's weight drug, which uses the generic anticonvulsant toperamate as one of two active ingredients.Vivus' shares, which had rallied earlier this week after the FDA's approval of Qsymia, fell 13% yesterday, Reuters reported. And Orexigen, which is in late-stage development of another combo pill against obesity, saw its own shares drop 10%.

But still with an estimated 30% of Americans considered obese, and even more considered clinically overweight, drug companies, and investors, can't help but expect to see big returns.

- here's the ABC News story

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