UPDATED: FDA hits green light on Vivus weight drug Qnexa

The FDA has given a green light to Vivus ($VVUS) to start marketing its weight drug Qnexa, firing the starting pistol in a race to commercialize one of the first new obesity drugs in 13 years. Vivus put out the word that it expects to start selling the drug in the fourth quarter, making it the first new weight drug to make its way to patients. And its stock surged more than 15% on the approval.

The news of the OK came early for Twitter followers, who were treated to the premature release of an embargoed story at USA Today, thanks to TheStreet's Adam Feuerstein. But the USA Today story neglected to spell out all the restrictions that would be placed on the drug, which has been linked to birth defects and an elevated heart rate.

In the FDA's statement, regulators note that women of child-bearing age who are taking the drug--to be branded as Qysmia--will need to be on birth control. And among six post-marketing studies that will be required regulators ordered a lengthy cardiovascular study to track any heart issues that could be associated with the drug, a combination of the appetite suppressant phentermine and an antiseizure drug, topiramate.

"Qsymia, used responsibly in combination with a healthy lifestyle that includes a reduced-calorie diet and exercise, provides another treatment option for chronic weight management in Americans who are obese or are overweight and have at least one weight-related comorbid condition," noted the FDA's Janet Woodcock.

The FDA is laying out some very specific dosing guidelines. Patients who don't lose 3% of their weight by week 12 on a recommended dose of 7.5 milligrams of phentermine and 46 mg of topiramate can go up on the dose, but  regulators want them to get off the drug if they haven't shed at least 5% of their weight after another 12 weeks of therapy.

In clinical studies patients taking Qysimia lost up to 9% of their weight, significantly more than the weight loss attributed to Arena's ($ARNA) lorcaserin, which won approval recently. Lorcaserin (Belviq) isn't expected to hit the market now until early 2013, giving Qnexa a chance to break out ahead. A third weight drug, Orexigen's ($OREX) Contrave, is undergoing an extensive FDA-ordered safety study ahead of any formal decision.

Still undecided is the price Vivus plans to charge for the drug. All President Peter Tam told USA Today was that the drug was unlikely to be covered initially by insurers and that the cost won't be "outrageous." The AP story, also evidently penned under the botched embargo, notes that Tam plans to sell the drug with a sales force of 150. And the launch plans include the use of an outsourced sales force from PDI.

A small company like Vivus, however, isn't the kind of company most likely to fully capitalize on a blockbuster drug. According to Bloomberg, Vivus is scouting for partners outside the U.S. And in a heated M&A environment, there's been plenty of speculation that a Big Pharma company could step in post-approval to snap up this product. Barclays estimates that the moribund obesity drug market could swell to $6 billion with the addition of new drugs.

Even with a revved up enrollment process, Orexigen isn't likely to get interim data from its safety study on Contrave until the second half of 2013, setting up a six-month FDA review. But Mike Narachi, the CEO of Orexigen, didn't sound too worried about the prospect of being the last of the three biotechs to hit the market.

He's gambling that Takeda's marketing muscle will be able to spread the word rapidly, engaging the 15,000 physicians known for writing prescriptions on weight loss drugs while the partners ramp up a weight loss program--similar to the kind of efforts seen in smoking cessation--which can engage patients over a prolonged period of time. Half of all the people who take a weight loss drug are non-responders, he adds, so you can expect plenty of switching--just as physicians see every day with antidepressants.

"Takeda has a history of growing blockbuster drugs," he told FierceBiotech, just ahead of today's approval for Qnexa. And he believes that regardless of the timing on the first two drugs, Contrave has plenty of blockbuster potential once it reaches its peak as the sales group makes its case with insurers and employers.

Soon after the news hit, Orexigen's shares climbed 6%, while Arena saw its stock slump by about the same amount.

- here's the press release
- read the AP report
- read the Bloomberg story