Coleman said it was clear a lot of panelists weren't strongly against the drug but just had "lingering concerns to make them vote no."
Meanwhile, several patients who were enrolled in Vivus' trial pleaded with the committee earlier in the day to approve the drug.
Erin Aycock, a young woman who took lost 50 pounds while taking phentermine/topiramate but gained back most of the weight when the trial was over, said the drug made losing weight easier than anything else she has tried.
"It's like instant willpower," Aycock said. "I have the ability for the first time in my life to say 'I don't even care if I eat that cookie.'
"I would do anything to be back on this drug."
As for Lorcaserin and Contrave, the other drugs set to go before the FDA, Wolfe said he's unsure about how they'll fare in front of the panel.
"The history of drugs for weight loss is littered with drugs that are dangerous," said Wolfe. "When a new drug comes to market, you know that it works, but you don't know about its side effects."
Fujioka said he hopes the FDA panel's meetings will provide guidance on drug safety issues and some insight about the future of other drugs.
"They'll give us an idea about how much safety will be required to get a drug approved," he said.
"What happens in this meeting affects the other drugs as well," he added.