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Weight loss trial design considered.

WASHINGTON -- Makers of antiobesity drugs fright see looser requirements for approval if the Food and Drug Administration adopts the recommendations of its Endocrinologic and Metabolic Drugs Advisory Committee, which met in early September.

The agency, which is revisiting its 1996 guidance on what's required to secure approval for weight loss drugs, sought the panel's input on clinical trial design issues.

Currently, FDA requires companies to study at least 1,500 patients for 1 year in placebo-controlled studies and then follow 200-500 of those patients for a second year in an open-label trial. These requirements are already stricter than those called for by an agreement between international regulators recommending that drugs for long-term treatment of non-life threatening conditions be studied only in 300-600 patients for 6 months, followed by a 100-patient, 1-year extension.

Advisory panel members said companies might be able to win approval with only 1 year of safety and efficacy data, as long as a separate, year-long study followed up later.

Most panel members said they were comfortable that efficacy--at least for short-term use--could be proven with 1 year of data, but they added that they would want to see more data to support longer-term use of weight loss drugs, especially in children. The data also should show at least a 5% greater weight loss than placebo, they said.

Dr. Glenn Braunstein of the University of California, Los Angeles, said he would not want a drug to languish in the approvals process if it showed efficacy in the first year. As far as long-term efficacy, "ultimately, I think patients will vote with their feet. If they regain the weight, they will go off the drug," he said.

Panel members expressed concern about safety problems that could crop up with wider use, as has been seen with many weight loss drugs. "The population that will eventually take obesity drugs is just massive," said Dr. David Orloff of the FDA's division of metabolic and endocrine drug products, in urging the committee to carefully consider how trials can adequately detect adverse events.

Advisory panel members said trials should be large enough to flag safety problems in 1 in 500 patients.

Ira Loss, an analyst who follows Washington developments that affect the pharmaceutical industry, said if the FDA adopts the panel's recommendations, Sanofi-Aventis might have a chance at getting approval for its obesity drug Accomplia (rimonabant) with data it's already compiled. Rimonabant and Regeneron Pharmaceuticals' injectable Axokine were both briefly discussed, as both have recently completed last-stage testing. Axokine helped patients lose 3.5 kg more than placebo, said Dr. Frank Greenway, a committee consultant from Louisiana State University, Baton Rouge. However, patients experienced injection-site reactions, nausea, and dry cough, he said.

Patients taking rimonabant have also experienced more nausea and diarrhea than those on placebo, Dr. Greenway said. Based on one published 16-week study, Dr. Greenway predicted that at 6 months, patients taking rimonabant would lose 5 kg more than those on placebo.

The market for weight loss drugs has fluctuated during the last 2 decades, spiking with approvals and dropping with high-profile recalls, said Laura Governale of FDA's division of surveillance, research, and communication support. At the mid1990s peak, 21 million prescriptions were written, largely for phentermine. By 2003, three drugs shared the relatively paltry market: Xenical (orlistat), with 1.3 million prescriptions; Meridia (sibutramine), with 752,000; and phentermine, with 3 million.

Third-party payment for weight loss drugs has grown since the late 1990s, with almost 30% of prescriptions paid by insurers in 2003, she said.
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Title Annotation:Clinical Rounds
Author:Ault, Alicia
Publication:Family Practice News
Geographic Code:1USA
Date:Oct 15, 2004
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