It ain't over 'til the fat lady sings. Unfortunately for VIVUS (Nasdaq: VVUS), the opera star is warming up backstage, and it's unlikely she'll be able to take the company's obesity drug, Qnexa, any time soon. 

In a move that slashed the pharmaceutical's shares, Food and Drug Administration advisory committee recommended that the agency not approve Qnexa, by a margin of 10 to 6. Or maybe it was 9 to 7; it depends on which vote you want to take as official. Either way, a majority of committee members thought Qnexa shouldn't be approved. The message from the panel is clear: Safety data is important. Really important.

One of the two components of Qnexa is Johnson & Johnson's (NYSE: JNJ) Topomax. Its side effects are apparently O.K. for migraine and epilepsy patients, but not for obese patients, where diet and exercise are available alternatives for shedding the pounds. After voting down sanofi-aventis' (NYSE: SNY) Acomplia a few years ago, it shouldn't come as much of a surprise that the panel is a little worried about another fen-phen.

Additional two-year safety data from a clinical trial is expected this quarter; whether it'll be enough to sway the FDA, which has the final say, is unknown at this point.

So where does this leave the other two obesity drugs -- Arena Pharmaceuticals' (Nasdaq: ARNA) lorcaserin and Orexigen Therapeutics' (Nasdaq: OREX) Contrave -- currently up for review at the FDA?

Contrave's chances for approval seem slimmer after this vote. The drug, which combines GlaxoSmithKline's (NYSE: GSK) antidepressant Wellbutrin and addiction treatment naltrexone, has side effects including nausea, which caused patients to drop out of the clinical trials. I have a hard time seeing the FDA viewing Contrave's risk-reward profile as better than Qnexa's, considering that the weight loss in patients taking Contrave wasn't as high as it was for those taking Qnexa.

Lorcaserin has fairly mild side effects, and more safety data, but provides a fairly minimal amount of weight loss. The advisory panel was focused on safety this week, but that doesn't mean panel members won't be focused on efficacy when they review lorcaserin in September. The high risk of not getting approved is the very reason I thought the company should have taken more up-front cash from Eisai.

In my article earlier this week, I warned that there are no easy layups from here. Half-court shots are even harder.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Johnson & Johnson is an Income Investor selection. Motley Fool Options has recommended buying calls on Johnson & Johnson. The Fool owns shares of GlaxoSmithKline and has a disclosure policy.