The FDA announced on September 16 that the highly anticipated weight loss drug, lorcaserin, was rejected by a panel of experts in a vote of 9 to 5. High hopes had been attached to the drug — particularly on Wall Street — as it was touted to provide significant weight loss with few side effects. This is the second of three weight loss drugs awaiting FDA ruling this year (the first being Qnexa, which was recently rejected).

Unable to decide on the drug’s fate themselves, the FDA had turned the matter over to a panel of experts, the Endocrinologic and Metabolic Drugs Advisory Committee, earlier in the week. The panel voted against the drug because of potential side effects that had not been revealed until earlier this week. Namely, lab rats who were given the drug developed tumors. The panel said this side effect was concerning enough to outweigh the weight loss benefit, which was sparse enough that it did not meet FDA criteria for a diet pill. Though the experts rejected the drug, the FDA technically does not have to follow their advice — though it usually does. A final decision will be made next month.

The drug is thought to work by affecting serotonin, a neurotransmitter in the brain thought to play a role in appetite and how the body metabolizes food.

Investors were apparently disappointed with the news, too, as shares for the company, Arena Pharmaceuticals, dropped sharply.

Arena’s president and CEO, Jack Lief, is quoted in the press release as saying, "We believe that lorcaserin has a positive benefit-risk profile and represents a potential advance in the treatment of obesity. We will work with the FDA as the agency completes its review of the lorcaserin new drug application."

While we await the FDA’s final decision, it’s probably a safe bet to continue with a tried-and-true method for weight loss: diet and exercise. It’s not always easy, but we know it works — and poses few side-effects, if taken in the proper dosage.