Could This Be the Next Big Diet Pill? And Will It Fry Your Brain?

Pharmaceutical companies have long been jockeying to produce the next awesome weight-loss drug that will make you lose control of your bowels and die. The quest suffered a major setback in 2010 when two drugs were rejected for little things like wiping people's memories and giving rats cancer. But now both drugs are back, and one is emerging as a frontrunner. Let's learn a little more about Qnexa, the drug that could be giving you heart palpitations very soon.

You remember Qnexa! It's impossible to pronounce (apparently [kyoo-nek-suh]), and it's made of a combination of phentermine (an appetite suppressant that's currently on the market and was half of the notorious fen-phen) and topiramate, which is used for epilepsy and migraines. In 2010, the FDA rejected Qnexa over concerns that it caused "suicidal thoughts, heart palpitations, memory lapses and birth defects." The agency asked for more data, and in December 2011, Qnexa developer Vivus released research on the drug's relationship to birth defects. Their study found that women who took topiramate in their first trimester of pregnancy had a 0.29% risk of having a baby with a cleft palate, compared to a 0.07% risk in the general population. Women who took the drug before but not during pregnancy still had a somewhat elevated risk, at 0.16%. This looked like bad news for Vivus, and its share price dropped. The company had already resubmitted Qnexa to the FDA, with a warning that it wasn't for women of childbearing age.

But this week, the FDA asked Vivus to remove that warning. If approved, the drug could be prescribed to women of childbearing age, as long as they weren't actually pregnant. It's unclear why the FDA saw fit to remove the warning, since Qnexa appears to approximately double the risk of cleft palates even when women take it before they get pregnant. A representative from the FDA's Office of Public Affairs told me the FDA doesn't comment on pending drug applications, so no help there.

Vivus is playing it cool by saying that the removal of the warning doesn't necessarily mean the FDA will approve Qnexa. But the company's stock price jumped at the news, and securities analyst Jason Butler told the AP the removal did signal that approval could be in the offing. He said that "women of child-bearing potential are currently the primary treatment-seeking population for medical obesity therapy," and that the FDA was becoming "more collaborative on the path to approval for obesity drugs in recent months." The agency is slated to announce its decision on Qnexa on April 17, so the drug could be coursing through America's bloodstream within the year.

This despite the fact that Vivus doesn't appear to have any new research to allay concerns about cardiovascular or mental-health side effects — at least, none that they've released publicly. One 2011 paper commissioned by the company, which argued that Qnexa was "very safe" despite the fact that some users reported depression and anxiety, turned out to be based on old data the FDA already had. Vivus's latest clinical trial, dubbed SEQUEL, does appear to have been modified in September 2011, but its "final data collection date" is listed as June 2010, well before the initial rejection. It's unclear whether Vivus actually has new data for the FDA, or whether it's just reinterpreting old numbers — a representative for the company couldn't comment beyond some general information about the drug.

Meanwhile, Qnexa's got a competitor on its tail. Lorcaserin, a drug also rejected in 2010 — because it didn't work very well and gave rats cancer — has also been resubmitted by its manufacturer Arena, and the FDA is scheduled to make a decision on its approval on June 27. And according to Seeking Alpha, Congress is pressuring the FDA to approve new obesity drugs. So for Vivus and Arena, this could be an exciting year. For people who like healthy hearts, brains, and pregnancies, the forecast is less clear.

Image by Jim Cooke.