SAN DIEGO ( TheStreet) -- Arena Pharmaceuticals ( ARNA) brings its weight-loss drug lorcaserin in front of an advisory committee of the U.S. Food and Drug Administration today.

Arena is trying to do what competitor Vivus failed to achieve in July -- convince a group of outside experts that the company has a weight-loss drug that is both effective and safe for the millions of obese Americans who can't seem to shed the pounds with diet and exercise alone.

In a review posted to the FDA's web site Tuesday, the agency's reviewers said lorcaserin provided only marginal weight loss for patients. The FDA also raised questions about the drug's safety and raised a concern about a potential cancer risk in animals.

The FDA's tough review spooked investors, sending Arena shares plunging. The stock closed Wednesday at $3.74, down 45% over the past two days.

Arena's stock will be halted today for the duration of the FDA advisory panel.

It's important to note that FDA drug reviews released ahead of advisory panel meetings are often sharply critical and sometimes do not accurately predict the ultimate vote of the panel's outside experts.

Arena's enters the fray of an FDA advisory panel amidst a regulatory environment obsessed with drug safety and (so far) unkind to obesity drugs. On Wednesday, eight experts siting on the same FDA advisory panel voted to withdraw Abbott Labs' ( ABT) weight-loss drug Meridia from the market, while another six panelists voted to restrict the drug's distribution. In July, a similar panel voted overwhelmingly against Vivus' drug Qnexa.

Arena will try to fight against this tide of skepticism over weight-loss drugs by citing lorcaserin's lack of serious side effects and two years of safety data showing patients are free from any additional cardiovascular safety problems. The company believes there is strong evidence to compel both the FDA and its advisory panel to support lorcaserin's approval. Next up, an FDA advisory panel will review Orexigen Therapeutics' ( GSK) obesity drug Contrave in December.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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