Vivus stock soars as weight-loss drug Qnexa approved by government panel

A panel of medical experts reversed their prior decision and approved Qnexa, a new drug designed to battle obesity.

This is the first time since 1999 that a new weight-busting drug is being introduced. The decision was a surprise reversal by the same panel which blocked the drug in 2010. At the time, the committee ruled that the risks of heart problems and birth defects outweighed its potential benefits as a weight-loss aid.

So what happened between then and now? The drug has not undergone any chemical alterations. It is still a combination of topiramate, an anticonvulsant used to treat migraine headaches, and phentermine, an appetite suppressant. The combination works synergistically by speeding up metabolism and suppressing hunger cues.

Topiramate is implicated in the increased incidence of birth defects, specifically, a two- to five-fold increased risk of cleft lip in babies exposed to the drug in utero. Phentermine has been found to speed up heart rate slightly, making the drug contraindicated in those susceptible to heart problems.

When an FDA advisory panel like this one rules against a drug, the maker of the medication can reapply for another review, provided it has addressed the panel’s concerns and objections. In this case, Vivus, Inc., the maker of Qnexa, resubmitted its application along with a proposal of a tightly controlled system for prescribing Qnexa. To prevent birth defects, Vivus recommends that patients taking the drug take monthly pregnancy tests, as is required of other drugs which are known to cause birth defects. Healthcare providers will receive special training about Qnexa’s risks and side effects. And Vivus will restrict the distribution of Qnexa to registered pharmacies.

Vivus proposed similar measures for cardiovascular risks.

"We will know who the prescribers are. We will know who has been trained," said Dr. Barbara Troupin, Vivus' senior director of global medical affairs, as she addressed the advisory committee. "We are confident the Qnexa [risk management program] balances the safeguards while allowing access for appropriate patients."

In a clinical trial involving 4,323 people, Qnexa led to an average loss of about 10% of total body weight in the first year of use.

Joe Nadglowski, chief executive of the Obesity Action Coalition, a patient advocacy group based in Tampa, Fla., which supports approval of Qnexa, said that "The simple reality is, if you're pregnant or planning on getting pregnant, it's not the right drug for you.”

The FDA will issue a final ruling on the drug later this year, but it generally follows the recommendations of its advisory committee.

If approved, Qnexa will be targeted for those with a Body Mass Index (BMI) of 30 and above, as well as those with a BMI of 27 if they have other risks such as diabetes.

Meanwhile, Vivus shares soared overnight to double the official closing price of $10.55. It is currently $18.99 as of the time of this writing.

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Image Source: Wikimedia Commons

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