At one point yesterday, Arena Pharmaceuticals (Nasdaq: ARNA) was up a maddening 22%. Shares ended the day up 6.5%. Even that's too much.

The reason for the buying spree? A press release about the company presenting data on its obesity drug, lorcaserin, at the European Congress on Obesity. The data presented at the medial meeting looks good; at two daily doses of lorcaserin, 46.3% (and 40.6% of single daily dosed) patients lost at least 5% of their body weight compared with 22.1% of patients on placebo. The Food and Drug Administration generally wants to see the drug group above 35% and double the control group.

But this wasn't new data. Arena combined the three phase 3 trials it ran for lorcaserin -- BLOOM, BLOSSOM, and BLOOM-DM -- to come up with the data. This type of meta-analysis might be interesting for researchers, but it isn't likely going to change the FDA's view of the drug. In fact, the inclusion criteria and analysis (Modified Intent-to-Treat with Last Observation Carried Forward analysis) for the meta-analysis sounds like something that would send shivers up the spine of FDA reviewers.

Arena still has an obese to-do list from the FDA before it'll sign off on the drug. And investors should keep in mind that there's no guarantee that Arena can satisfy the agency. I foresee the FDA being sticklers about every single item; the agency hasn't exactly been kind to the other obesity drug developers: VIVUS (Nasdaq: VVUS), Orexigen (Nasdaq: OREX) and Abbott Labs (NYSE: ABT).

Arena has four other drugs in its pipeline. They're all in phase 1 development, but at this point, investors would likely be better off watching those than reacting to meta-analysis data for lorcaserin.

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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. Motley Fool newsletter services have recommended buying shares of Abbott Laboratories. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.