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Fen-Phen Risks Won’t Color U.S. FDA Diet Pill Review

Arena Pharmaceuticals, Inc.
Lorcaserin tablets are manufactured by Arena Pharmaceuticals. Source: PR Newswire

U.S. regulators won’t re-examine safety data from fen-phen, the recalled diet drug tied to heart damage, as they review a new generation of weight-loss pills led by Vivus Inc.’s Qnexa that use some of the same ingredients.

The Food and Drug Administration doesn’t need to revisit fen-phen’s risks because none of the new treatments contain the same chemical mix, Eric Colman, deputy director of the agency’s Division of Metabolism and Endocrinology Products, said today in a telephone interview.

Qnexa and Arena Pharmaceuticals Inc.’s lorcaserin have individual components similar to those blended to make fen-phen. Orexigen Therapeutics Inc.’s Contrave, the third diet drug under FDA review this year, contains an antidepressant and addiction drug tied to nausea, vomiting and dizziness. If the new medicines prove safe, the global diet-pill market may reach $10.5 billion by 2018, according to Datamonitor Plc in London.

“To the best of our knowledge, the concern with the heart valves was limited to fenfluramine and dexfenfluramine,” two fen-phen ingredients that were banned from the market in 1997, said Colman, who started in his division 15 years ago as risks from the treatment were emerging. “It was a very specific finding.”

Shares Surge

Shares of Vivus, based in Mountain View, California, surged 12 percent, or $1.16, to $10.67 at 4 p.m. New York time in Nasdaq Stock Market composite trading, the biggest single-day increase in more than two months. Arena increased 4.3 percent, or 15 cents, to $3.64. Orexigen climbed 6.4 percent, or 25 cents, to $4.15. Orexigen and Arena are based in San Diego.

“How many more drugs have to bite the dust in this category?,” Sidney Wolfe, health research director of the Public Citizen consumer group in Washington, said today in a telephone interview. “Weight loss is a long-term concern and therefore if someone is arguably going to be taking a drug for a long time you need to have long-term safety studies.”

An FDA advisory panel is set to meet July 15 to evaluate Qnexa, the first of three pills facing review this year. A review for Arena’s lorcaserin is scheduled for Sept. 16, followed by Orexigen’s Contrave on Dec. 7. The FDA usually follows the panel recommendations, though it isn’t required to do so.

Medical products designed to help in weight management should help people lose at least 5 percent more weight than a placebo after one year, according to FDA recommendations released in 2007. While “specialized safety assessments” such as evaluating neurological function or immune-system response may be appropriate for some drugs, the guidelines don’t specify what side effects should be tolerable.

‘Loss at Any Cost’

“‘What should you risk to lose weight?’ has been refined” since fen-phen, said Madelyn Fernstrom, director of the University of Pittsburgh Medical Center Weight Management Center, in a June 25 phone interview. “We’re not so convinced that we want to have as many side effects. It’s not weight loss at any cost.”

Sales of prescription weight-loss drugs fell 11 percent last year to $153.7 million, according to the research firm IMS Health Inc. in Norwalk, Connecticut. Of the almost 7.5 million prescriptions dispensed, four of every five were for generic phentermine, a component of fen-phen still sold as a short-term appetite suppressant.

Two-thirds of American adults are overweight, raising their risk of diabetes, heart disease, high blood pressure and cancer, according to the 2008 National Health and Nutrition Examination Survey. More than one-third of American adults are obese, measured as a ratio between height and weight.

‘Lingering Safety Issues’

Colman said the FDA doesn’t think any drug will “cure the obesity problem in this country” and expects some side effects to emerge after drugs are on the market and used in a broader population. The agency gained new authorities in 2007 that allow it to require companies to do additional studies after approval to examine “lingering safety issues,” he said.

“One thing we’re always saying to people but it doesn’t necessarily sink in is that we certainly don’t know everything about a drug when it is approved,” Colman said. “More often than not, there will be safety issues that arise.”

Qnexa combines phentermine with the anticonvulsant drug topiramate, the generic form of Johnson & Johnson’s Topamax. The experimental drug helped people lose an average of 14.7 percent of their body weight, in a 56-week study of 1,267 morbidly obese patients, compared with 2.5 percent on placebo. A second study of 2,487 overweight and obese patients with high blood pressure, high cholesterol or diabetes linked Qnexa to an average weight loss of 13.2 percent, compared with 2.4 percent on placebo, according to data released by Vivus in September.

Common Side Effects

The most common side effects were dry mouth, tingling, constipation, altered taste and insomnia. There were no signs of suicidal behavior, a danger seen with Topamax and other epilepsy medicines.

“The current industry guidance for developing obesity drugs suggests Qnexa will be approved,” said Christopher S. James, an analyst at McNicoll Lewis & Vlak LLC in New York, in a June 25 note to clients. “However, our view is that advisory panels will be tough on the safety of all obesity drugs.”

A vote to recommend approval of Qnexa “without too many complications” probably will boost shares of Arena and Orexigen as investors gain confidence that the FDA will look favorably on new drugs for obesity, said Steve Yoo, an analyst with Leerink Swann & Co. in New York, in a June 23 research report.

Similar to Fenfluramine

Lorcaserin is similar to fenfluramine, and binds to the same receptor in the brain that controls appetite, while avoiding a separate target in the heart that was linked to valve damage with the recalled treatment, according to Arena. Tokyo- based drugmaker Eisai Co. bought marketing rights to Arena’s drug on July 1.

To make Arena’s pill more effective, it will likely “be used in combination with phentermine as part of a ‘21st century fen-phen’ combination,” Yoo said. “Even though the original fen-phen combination was a medical and product liability fiasco, weight loss of as much as 15 percent was possible.”

Orexigen’s Contrave adds a sustained-release version of the smoking-cessation and depression treatment bupropion to naltrexone, used for alcohol and opiate addiction.

Wyeth, acquired by Pfizer Inc. in October, set aside more than $21 billion to resolve almost 200,000 lawsuits involving fen-phen.

“There’s enormous pent-up demand” from doctors, said Michael Narachi, chief executive officer of Orexigen, in a June 29 interview. “They’ve been disappointed. The promise of new tools with good data will convince them to use” these products.

Download: FDA's Colman Interview

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