A panel of medical experts voted overwhelmingly Wednesday to endorse the controversial weight-loss drug Qnexa, clearing the way for the Food and Drug Administration to approve a new prescription obesity medication for the first time since 1999.
The FDA will issue a final ruling later this year, but the agency typically follows the recommendations of its advisory committees.
The 20-2 vote in favor of Qnexa was a surprising reversal from 2010, when the same advisory committee decided that the drug's risks of heart problems and birth defects outweighed its weight-loss benefits.
In a clinical trial involving 4,323 people, Qnexa — a combination of the anticonvulsant drug topiramate and the appetite suppressant phentermine — led to an average loss of about 10% of total body weight in the first year of use. Many users also saw improvements in blood pressure.
But the trials also found that that the drug caused a slight increase in heart rate, which can boost the odds of a heart attack or stroke. In addition, researchers detected an increased risk of birth defects — typically cleft lip — in women who became pregnant while taking the drug.
Vivus Inc., the drug's manufacturer, addressed those concerns by proposing a tightly controlled system for prescribing Qnexa. To prevent birth defects, patients who take the drug will have to undergo monthly pregnancy testing and healthcare providers will get special training on the medication's risks and benefits. Vivus will also restrict distribution of the drug to registered pharmacies, among other measures.
"We will know who the prescribers are. We will know who has been trained," Dr. Barbara Troupin, Vivus' senior director of global medical affairs, told the advisory committee. "We are confident the Qnexa [risk management program] balances the safeguards while allowing access for appropriate patients."
According to the clinical trial data and previous studies, the risk of having a baby with a cleft lip is two to five times greater in women who took topiramate.
"The simple reality is, if you're pregnant or planning on getting pregnant, it's not the right drug for you," said Joe Nadglowski, chief executive of the Obesity Action Coalition, a patient advocacy group based in Tampa, Fla., that supports approval of Qnexa.
Vivus, based in Mountain View, Calif., proposed a similar program to monitor heart risks in patients. Several panel members strongly encouraged the company to conduct a post-marketing study to help identify the potential cardiovascular risks.
At the panel's daylong meeting Wednesday in Silver Spring, Md., several members of the Endocrinologic and Metabolic Drugs Advisory Committee said they worried about Qnexa's side effects but believed the benefits outweighed the risks.
More than 35% of American adults are obese, including about 5% who are morbidly obese, and an additional 33% are overweight, according to the Centers for Disease Control and Prevention in Atlanta. Those extra pounds are more than just a cosmetic issue; they also increase one's risk of diabetes, heart disease, stroke, osteoarthritis, certain types of cancers and possibly dementia.
"The most encouraging thing is that just about every member really heard the message about the need to treat obesity," said Ted Kyle, the advocacy committee chairman of the Obesity Society. "Obesity is not a trivial disease."
Only one prescription diet drug is available in the United States. That drug, orlistat, blocks absorption of fat and is sold under the trade name Xenical. Qnexa appears to work by suppressing appetite and increasing feelings of fullness.
It's not clear why the medication raises heart rate, but such an increase is typically viewed as a marker of cardiovascular risk, said Dr. Michael S. Lauer, director of the division of cardiovascular sciences at the National Heart, Lung and Blood Institute and a member of the advisory panel.
Lauer cast one of the two votes against approval, saying that the FDA should first ask Vivus to complete a study that provided detailed cardiovascular risk data. Otherwise, he said, FDA approval "would be a decision based on hopes, surrogates and suppositions."
"We have seen many cases in medicine where we thought we understood the pathology of disease … and we turned out to be wrong," Lauer said. "With an epidemic as serious as obesity, we need to do this right."
If approved by the FDA, Qnexa would be targeted for people with a body mass index of 30 or above, or a BMI of 27 or above for people who also have weight-related health problems, such as diabetes or sleep apnea. A BMI of 25 to 29 indicates a person is overweight, and 30 or greater is considered obese.
The vote sent Vivus shares soaring to more than $21 in after-hours trading, double the official closing price of $10.55.