Two Old Drugs Make One New Diet Pill

Sept. 10, 2009— -- Patients taking a novel diet drug that combines the stimulant phentermine with the anticonvulsant topiramate lost an average of 37 pounds over a year with significant improvement in a number of heart risk factors, according to an announcement Vivus, the developer of the drug.

In a trial known as EQUIP, which involved more than 1,200 morbidly obese patients, patients who received the drug, which has the brand name Qnexa, lost weight at every tested dose, but significant weight loss -- 14.7 percent on average -- occurred at the highest dose.

Results from a second trial involving 2,487 overweight and obese patients with hypertension, hyperlipidemia, or type 2 diabetes, known as CONQUER, showed an average weight loss 30 pounds with full dose of the drug combination.

When asked by ABC News and MedPage Today for a comment on the scant data reported by the drugmaker, Dr. Mitchell Roslin of Lenox Hill Hospital in New York called the results very impressive, noting that the reported weight loss approached that of the Fen-Phen combo drug that swept the diet drug market in the early 1990s.

But Fen-Phen fell as fast as it rose when the fenfluramine, which was the "Fen" in Fen-Phen, was linked to pulmonary hypertension and serious heart valve problems, which led to the drug's withdrawal from market amid an avalanche of lawsuits.

Phentermine, a stimulant that acts as an appetite suppressant, has remained on the market, although as Roslin said, "it can increase blood pressure or make people feel jumpy."

Dr. Carl Lavie of the Ochsner Heart and Vascular Institute in New Orleans also raised the caution flag about cardiovascular side effects of phentermine, which he said also has the potential to "cause rhythm disturbances."

Topiramate is best known as an epilepsy drug, but Roslin said that it gained off-label traction when several published studies suggested the anticonvulsant had a beneficial "effect on binge eating and weight reduction."

But Roslin said at least one company decided against pursuing a weight loss indication for topiramate when clinical trials found that while the drug did help people shed pounds, side-effects included drowsiness and memory problems.

"Thus the results of the combination are impressive," Roslin said.

Lavie, agreed, noting that obesity itself is a major cardiovascular risk factor and the weight loss reported in EQUIP and CONQUER was "generally more than typically reported with other non-surgical therapies."

But a number of questions were left unanswered by the data released by Vivus. Among these was the question: Will rebound occur when the drug is stopped?

Short-term safety looked good, Roslin said, but as long term use is needed to maintain weight loss, safety could become an issue.

Leland Wilson, president and CEO of Vivus said that based on the results from EQUIP and CONQUER trials which were "designed and executed after Special Protocol Assessments were completed by the FDA," the company will file a New Drug Application with the FDA by the end of 2009.