SILVER SPRING, Md.—For the second time in less than three months, an expert panel convened by the US Food and Drug Administration voted to recommend approval of a prescription weight loss drug that had previously been rejected because of safety concerns: Lorcaserin (Lorqess) was approved Thursday by an 18 to 4 vote with 1 abstention for its ability to help overweight people shed pounds with few apparent side effects.

While lorcaserin leads to more modest weight loss than Qnexa—which won a thumbs-up from the same FDA panel in February—it has been associated with safety concerns over heart risks and birth defects in women who become pregnant while taking the drug.

If ultimately approved by the FDA, which usually follows the advice of its advisory panels, lorcaserin and Qnexa could be the first prescription weight loss drugs in 13 years, adding to the single drug that is currently on the market.

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Lorcaserin had been voted down by experts two years ago after initial animal studies showed increased cancer risks, but those concerns were largely laid to rest with followup data submitted by the manufacturer Arena at the meeting on Thursday; the FDA concluded that the risk of tumors in those taking the drug was “negligible.”

The possibility remains, however, that lorcaserin could raise the risk of hypertension in diabetics or damage heart valves, a potentially deadly side effect seen in older weight-loss pills that were withdrawn from the market.

“This drug met the critera that the FDA set for approval,” said panel member Dr. Eric Felner, a pediatric endocrinologist at Emory University who voted in favor of putting Lorqess on the market. “But I think patients on it need to be monitored by seeing their doctors every two to three months and having an echocardiogram to check their heart function two or three times a year.”

Clinical trials weren’t designed specifically to look at heart risks, so the experts agreed that patients taking the drug should have frequent heart screenings until more is known from followup studies.

In clinical trials, patients taking lorcarserin lost an average of 8 percent of their body weight, or 18 pounds, after one year, compared with a 7-pound loss in the placebo group. Slightly less than half of the lorcarserin takers lost 5 percent or more of their body weight compared with about a quarter of those taking a placebo.

Those taking Qnexa in clinical trials, on the other hand, lost an average of 10 percent of their body weight, with more than 83 percent of patients losing 5 percent of their weight or more.

Whether the modest amount of weight lost on lorcarserin actually leads to better health outcomes—such as fewer complications from diabetes and heart disease—remains unknown.

Dr. Sanjay Kaul, a cardiologist at Cedars-Sinai Heart Institute who voted against approval, said he wasn’t convinced that the small amount of weight loss was “clinically meaningful” and that “the potential benefits would outweigh the risks when the drug was used long-term.”

The FDA is expected to make a decision on approval of lorcarserin in early summer. About a month ago, the agency pushed back its date for a final decision on Qnexa for three months until mid-July, saying it needed more time to review a safety plan submitted by manufacturer Vivus.