Arena Pharmaceuticals (Nasdaq: ARNA) could have used a touchdown from its Bloom-DM study testing its obesity drug, lorcaserin, in diabetics, but it looks more like a field goal.

Diabetics taking lorcaerin lost 3% more of their body weight than those on placebo. The "marginal" benefit that the Food and Drug Administration was worried about when it turned down lorcaserin last month hasn't really changed.

The drug was able to decrease HbA1c levels, a measure of blood glucose, by half a percentage point more than placebo. As a diabetes drug, that wouldn't be all that impressive, but since lorcaserin's primary role is weight loss, the decrease is meaningful and worthy of a three-point success.

The only potential game-changing fumble is lorcaserin's ability to adversely affect heart valves. The numbers were higher for patients taking lorcaserin than those taking placebo, but the study is so small -- 256 patients on lorcaserin and 253 on placebo -- that it appears more like randomness than anything else. Investors shouldn't ignore the difference, though; the safety-conscious FDA has the final call, and no one knows what the instant replay will show.

Overall, the Bloom-DM study leaves Arena in a slightly better position than it was in before the data was released, but this battle to get lorcaserin approved is far from over. There's still the rat cancer issue, and even if Arena clears it up, it's still not clear if the risk-benefit analysis is tipped far enough in favor of the benefits. Just look at GlaxoSmithKline's (NYSE: GSK) Avandia and Abbott Labs' (NYSE: ABT) Meridia to see how the FDA is calling them recently.

Investors looking for a piece of the obesity market would be better off looking at VIVUS' (Nasdaq: VVUS) Qnexa. The drug isn't in good enough shape that it's running out the clock waiting for an FDA approval, but the path to approval seems considerably clearer. Let's say it's in the red zone. The third candidate, Contrave from Orexigen Therapeutics (Nasdaq: OREX), is a bit of a wild card, but we'll know more after the FDA advisory panel has its say on Dec. 7.

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The Fool owns shares of and has written covered calls on GlaxoSmithKline, which is a Motley Fool Global Gains selection.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. 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 Fool has a disclosure policy.