In my preview of the Food and Drug Administration advisory panel reviewing VIVUS' (Nasdaq: VVUS) Qnexa, I said the panel members reviewing the obesity drug needed to support the approval of in "confident and outspoken enough terms to convince the agency."

Yeah, I'd call a 20-2 vote in favor of recommending approval confident enough to convince the FDA to approve the drug that it rejected in late 2010.

Ultimately, the panel said, the advantages of weight loss trumped potential heart issues and the risk of birth defects could be managed with a risk-management plan that included female patients taking a pregnancy test.

A positive vote isn't enough to gain approval; it's only a recommendation, after all. A panel recommended approval of Orexigen Therapeutics' (Nasdaq: OREX) obesity drug Contrave by a margin of 11-8, but the FDA still sent the company back to the drawing board, ultimately requiring a large per-approval trial that the committee felt could be accomplished after the fact.

The difference for VIVUS could be the magnitude of the vote. The risk of the FDA going against the panel goes down substantially with each vote recommending approval.

But VIVUS still has some work to do. There are details to be worked out for the risk-management plan to ensure pregnant women avoid taking the drug and VIVUS' commitment to do a post-marketing trial to check for heart issues. The latter is likely the bigger worry, since heart problems discovered post-marketing is what brought down both Wyeth's Phen-Fen and Abbott Labs' (NYSE: ABT) Meridia. The agency will need to be convinced that data will come in quick enough to limit the number of people being exposed to Qnexa before the trial's results. Abbott's trial for Meridia took seven years to read out, which isn't going to cut it here.

An approval of Qnexa would generally be good news for Orexigen and Arena Pharmaceuticals (Nasdaq: ARNA), which have an obesity drug that's under review by the FDA, since it means the FDA is moving away from its hard-nosed stance on risks. But keep in mind that Qnexa has the best efficacy data of the three, so to meet the new risk-benefit level, the other two drugs will need to be deemed safer than Qnexa. Orexigen can certainly do it with data from its pre-approval heart safety trial. Whether Arena can convince the FDA that its drug's potential cancer issues are just an artifact remains to be seen. We'll know later this year, when another panel of outside experts convenes to review the drug.

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