VIVUS (Nasdaq: VVUS) plans to send its obesity drug Qnexa back in front of the Food and Drug Administration next month. You'll recall that the FDA took issue with the fact that one of the ingredients in Qnexa -- topiramate, the active ingredient in Johnson & Johnson's (NYSE: JNJ) Topamax -- might cause birth defects. VIVUS said the company "reached agreement" with the FDA on a plan to seek approval just for men and women without child-bearing potential before completing Fortress, its retrospective study examining the effects of topiramate on fetuses.

What exactly "reached agreement" means is only clear to those in the meeting between the company and the agency. Was it a "sure we'll look at the data, just send it in along with the PDUFA fee"? Or a more reassuring "most of the patients in your clinical trials were women, but you still have enough data to justify approving it for a group of patients that you didn't run a large prospective trial on"?

I have a hard time imagining the FDA saying the latter, but who knows.

By excluding women of child-bearing age, VIVUS says that it'll lose less than a quarter of the potential obese and overweight population that would be eligible to take Qnexa. While I don't doubt its claim, the fraction it would lose of those who would actually take the drug -- as opposed to those who would be eligible to -- is probably much greater, if the enrollment in the clinical trial is an indication of demand. In one of its pivotal trials, 83% of the subjects were women with an average age of 43.

Even if this is a shot in the dark at a much smaller indication, it's not the worst idea I've heard. If Qnexa's potential is only 10% of what it could be with a full indication -- just a guess -- it's still a decent-sized market. And some revenue from a drug is better than no revenue, especially for a company the size of VIVUS.

Resubmitting also allows the company to get formal feedback from the FDA on the other issues in the complete response letter, including potential heart problems. The agency told fellow obesity-drug maker Orexigen Therapeutics (Nasdaq: OREX) that it would have to run an insanely large trial to prove that its drug wasn't causing heart problems. Will VIVUS and Arena Pharmaceuticals (Nasdaq: ARNA) be held to the same standard?

It just seems like this is a no-lose situation for VIVUS -- besides the $770,000 or so for the PDUFA fee, of course. If Qnexa gets approved, great. If not, VIVUS will have a better understanding of what it needs to do when it's able to resubmit after its Fortress study is validated in the third quarter of 2012.

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