When the Food and Drug Administration posts the documents for an advisory committee meeting, I like to read the proposed questions for the panel before diving into the FDA's briefing documents. It's kind of like reading the last chapter of a book first: It spoils the suspense, but gives you a big clue as to what to expect.

For Arena Pharmaceuticals' (Nasdaq: ARNA) obesity drug, lorcaserin, the questions themselves didn't provide any clues as to the outcome of the meeting. And that's a good thing. Unlike the last advisory panel meeting for lorcaserin, when the FDA surprised investors with preclinical cancer data, the four questions before the obligatory one about whether to approve the drug all cover issues that were known before.

There are two questions on the two types of cancer -- mammary tumors and brain cancer -- seen in animal models, but the briefing documents seem to hint that the FDA is no longer worried about the issues. Kudos to Arena; it isn't easy to prove that a preclinical finding isn't real and/or relevant to humans.

Covered in the third question is the potential for lorcaserin to cause heart valve problems, which is still an issue. Preclinical work the FDA asked Arena to do suggests the drug is hitting the right target and shouldn't cause any problems, but Arena added more clinical data since the last review and the theoretical risk now exceeds the potential 50% increase in valvular heart disease that the FDA asked Arena to rule out.

Since the FDA will likely make Arena run a post-marketing heart study based on the advisory panel meeting in March -- the fourth question -- the panel might shrug off the heart valve issue. The data didn't miss the FDA's cutoff by much, and the 50% increase is all theoretical anyway. Looking at the statistics, lorcaserin could theoretically be preventing heart valve damage. Of course, heart issues caused by fen-phen and Abbott Labs' (NYSE: ABT) Meridia were discovered after the drugs were on the market, so the panel may not be so quick to dismiss the valve issue. The FDA is making Orexigen (Nasdaq: OREX) check its obesity drug for the potential to cause heart problems before approval because a heart signal was seen in the phase 3 trial.

The fact that there's only one voting question is probably a positive for lorcaserin. Since the first four questions are all safety related, any panel member who voted negatively on one of the four would have to vote against approval. By just asking the committee members for their opinion, they can be wishy-washy with their answers and still ultimately vote in favor of approval.

Figuring out which way the committee will go is tough. Lorcaserin produces less weight loss than VIVUS' (Nasdaq: VVUS) Qnexa, and the theoretical safety issues can't be removed by limiting the population that takes the drug like they can with Qnexa. But lorcaserin doesn't have to be as good as Qnexa, which breezed through its last advisory panel meeting; it only needs about three-quarters of the panel members to vote yes for investors to feel confident the agency will follow the recommendation.

If it sounds like I'm being wishy-washy in presenting both sides of the argument, that's because I am. Advisory panel meetings are difficult to predict, and they've been doubly hard for obesity drugs where the risk-benefit ratio is very subjective. My guess is a majority of panelists will vote in favor of approval, but it might fall in the 50% to 75% range, which isn't exactly a ringing endorsement and will keep the suspense over whether the drug gets approved going for a little while longer.

Fool contributor Brian Orelli holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool owns shares of Abbott Laboratories. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.