Talk about an obese FDA advisory committee meeting. Starting tomorrow, the Endocrinologic and Metabolic Drugs Advisory Committee will spend two whole days discussing the need for clinical trials to determine heart risks for obesity drugs.

It seems ironic that this committee meeting comes 15 years after fen-phen was pulled off the market because of potential heart valve problems. For an agency that most investors would characterize as overly cautious, the FDA sure took its time. Of course, since then, heart data on Meridia, which Abbott Labs (NYSE: ABT) pulled off the market in the U.S., has come to light. And the FDA decided to require diabetes drugs to prove they weren't causing heart problems like GlaxoSmithKline's (NYSE: GSK) Avandia.

Approval decisions for VIVUS' (Nasdaq: VVUS) Qnexa and Arena Pharmaceuticals' (Nasdaq: ARNA) lorcaserin -- the second for both -- will come after the meeting, but the vote won't have a formal effect on the companies. It'll take awhile for the FDA to integrate the committee's opinion into some sort of official guidance for drugmakers. After waiting for so long, what's a few more months?

Indirectly though, what the advisors say, especially if they vote in favor of requiring a pre-approval trial, could weigh on the FDA's decisions about Qnexa and lorcaserin in the coming months.

I think it's likely we'll see a requirement that a heart trial be run for all obesity drugs. The only question is whether the trial needs to be run pre-approval or post-approval. VIVUS seems to be planning for that inevitability; at the advisory panel meeting for Qnexa, the biotech said it already has plans to run a post-approval trial.

If the advisory panel backs away from a requirement of a pre-approval trial, I'd be cautious about assuming the FDA will follow suit. Remember, the advisory panel said Orexigen's (Nasdaq: OREX) Contrave should be approved and asked to do a post-approval trial, but the agency overruled the advisory panel and turned down the drug until the company ran a large pre-approval trial.

The cost of development is essentially the same pre- or post-approval, but a post-approval requirement would clearly be better for companies because they could have revenue coming in while they wait for the heart data.

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