Qnexa – Combination Weight-Loss Drug Meet Challenges to FDA Approval
Vivus Inc has released promising results for their Phase 3 clinical trial CONQUER which was designed to evaluate the safety and efficacy of their new investigational weight loss drug Qnexa. Despite Qnexa’s promising results, the FDA is fearful of unpredictable and dangerous side effects and has been hesitant to approve many weight loss products, including Qnexa.
Qnexa is a controlled-release combination of phentermine (FDA approved for short-term weight loss) and topiramate (FDA approved for epilepsy and migraines). The CONQUER trial studied the amount of weight loss overweight or obese subjects experienced with two different doses of Qnexa compared to placebo.
Nearly 2500 overweight or obese study participants patients with two or more weight-related disorders such as high blood pressure, high cholesterol, or type 2 diabetes were enrolled. Study volunteers were between the ages of 18 and 70 and were randomly assigned to one of three treatment options. Patients received a once daily pill containing either placebo (no drug), 7.5 mg phentermine and 46 mg topiramate, or 15 mg phentermine and 92 mg topiramate. Patients received medication and weight monitoring for 56 weeks.
At the end of 56 weeks, study participants that received the higher dose of Qnexa lost more weight compared to the other treatment groups. On average people in the high dose Qnexa group lost 28lbs compared to 4 lbs for the placebo group and 22 lbs for the lower dose Qnexa group.
While only 7% of patients that received placebo lost more than 10% of their body weight, 48% of patients treated with the higher Qnexa dose lost more than 10% of their body weight, and 37% of patients receiving the lower Qnexa dose lost more than 10% of their body weight.
Doctors also saw improvement in patient health with Qnexa. Bad cholesterol levels decreased for study participants that received Qnexa. Researchers also saw a significant decrease in high blood pressure for those who received Qnexa compared to those that got placebo. These patients were able to decrease the number of blood pressure medications they were taking.
The most common side effects for Qnexa were dry mouth, constipation, and tingling or numbness. The higher the dose of Qnexa, the more likely study participants were to experience these side effects.
Unfortunately, when the FDA reviewed CONQUER trial data for Qnexa in June 2010, they voted against approving the combination drug therapy for weight loss. The FDA has become increasingly more cautious about the approval of weight loss drugs after dangerous side effects were discovered for other popular diet pills, such as Fen-phen, Meridia and Alli. Fen-phen was taken off the market in 1997 after scientist linked its usage to heart valve disease.
Meridia has been linked to an increased risk of heart attacks, strokes and other cardiovascular problems; it was taken off the European market in 2009. Orlistat which is marketed as the prescription product, Xenical, and the over-the-counter (OTC) product, Alli, is linked to severe liver damage. The FDA has issued a safety warning for physicians and patients who might consider using Orlistat.
Its not surprising that the FDA was hesitant to approve Qnexa. Weight-loss drugs have a history of dangerous side effects and one of the main ingredients of Qnexa is phentermine, which is one of the main ingredients in the diet pill Fen-phen which has been withdrawn from the market. Until the FDA and pharmaceutical scientists and clinicians can make predictions about the likelihood of dangerous side effects from Qnexa and other new weight loss drugs seeking approval, we can expect for the approval process to remain painfully cautious.