FDA panel votes in favor of earlier rejected anti-obesity drug Qnexa

By Dr. Ananya Mandal, MDFeb 26 2012

Vivus Inc has soared in its market value on Thursday by nearly 80 percent as its weight loss pill Qnexa gets FDA support.

Qnexa took a step closer to approval on Wednesday, when outside advisers to the U.S. Food and Drug Administration voted 20-to-2 in favor of approval. The panel also recommended the company conduct a study to scrutinize even more closely any risk of heart problems. That study may be required after the drug is approved. Should the FDA ask for further data on heart risks before any approval, it would delay Qnexa's launch further.

Qnexa combines the stimulant phentermine with the epilepsy drug topiramate, sold under the brand name Topamax. It helped patients lose at least 10 percent of their weight after a year of treatment.

Some prominent FDA panel members recommended the study be conducted after approval. “I think is a benefit-risk trade-off question,” Dr. Sanjay Kaul, professor in the division of cardiology at Cedars Sinai Medical Center in Los Angeles, said during the panel discussion. “I would say that of all the obesity drugs, this drug has the highest efficacy in terms of weight loss. This shifts the balance more in favor of requiring a post-approval rather than pre-approval study.” However, if FDA ultimately decides to ask for the study before approval, Kaul said “it would not be unreasonable.”

FDA reviewers said patients taking Qnexa had more safety problems, including memory loss and higher heart rates, than those taking a placebo, though Vivus said there is no conclusive link between increased heart rate and heart health. The company also noted that the drug reduced blood pressure. High blood pressure can increase the risk of heart attack. From a medical standpoint, the risk of cardiovascular problems from taking Qnexa are being weighed against the heart, and other health risks, such as diabetes, associated with obesity.

The FDA has not approved a weight loss drug in the past 13 years and has withdrawn from the market many drugs due to concerns over heart risks and other side effects. Qnexa was rejected by the agency in 2010 after a 10 to 6 vote against approval by the same panel, which included about half of the same members as Wednesday's. But the panel this week agreed that the health risks of obesity and the benefits of losing weight outweighed the risks posed by the drug.

“The approval of Qnexa is a major step forward for the field of obesity treatment and is the result of advances in our understanding of the health consequences of obesity, and the resistance mechanisms that make it difficult to lose weight,” said Dr. Louis Aronne, director of the Comprehensive Weight Control Program at New York Presbyterian Hospital.

“This is far from a great drug,” said Dr. David Katz, director of the Yale Prevention Research Center. “The FDA panel recommended approval of Qnexa only because the ranks of useful weight loss drugs are so thin, and desperate times call for desperate measures. Approval of Qnexa would reflect that...desperation.”

One-third of Americans are obese and have chronic, expensive health problems as a result – diabetes, heart disease and arthritis, to name a few. Patients and doctors are often frustrated by the lack of middle ground options between traditional recommendations for diet and exercise and the more extreme approach of bariatric surgery.

“The approval of Qnexa feeds into a quick-fix approach to weight management,” said Dr. Gerard Mullin, associate professor at Johns Hopkins School of Medicine. “The solution to the overweight-obesity epidemic lies not in another effortless 'quick fix' but in a painful but permanent lifestyle solution.”

“There is an urgent need for better pharmacologic options for individual patients with obesity,” said Dr. Elaine Morrato, of the University of Colorado. “I believe Qnexa demonstrated a meaningful efficacy benefit and that there are consequences to not treating obesity.”

“I believe that this combination is different and a significant advance from any agents used in the past for weight loss,” said Dr. Chip Lavie, medical director of cardiac rehab and prevention at the Ochsner Clinic Foundation in New Orleans. “Considering the dismal results that many experience with attempted weight loss with diet and exercise, which is always the first choice, and the explosion in the need and use of bariatric surgery, this combination drug should be a major advance.”

Along with heart safety, panelists raised concerns about potential birth defects in women who become pregnant while taking Qnexa: topiramate is known to more than double the risk of birth defects. There were 34 pregnancies among 3,386 women enrolled in Vivus' studies of Qnexa, despite precautions to make sure women used contraception. An FDA expert on birth defects estimated there would be five babies born with a cleft lip defect for every 1,000 women who became pregnant while taking Qnexa. If approved, FDA scientists said they would require Vivus to train prescribers to educate patients on the pregnancy risks of Qnexa. The drug would only be available from 10 mail-order pharmacies.

The FDA will decide whether or not to approve Qnexa by April 17. Although the agency usually follows the recommendations of its panels, the drug's fate is not assured.