If you were hoping that diet drug rimonabant (Acomplia / Zimulti) would be approved for treatment of "metabolic syndrome" so your insurance company would be more likely to pay for your weight-loss efforts, the current thinking at the U.S. Food and Drug Administration does not appear very encouraging.

The FDA’s Metabolic and Endocrine Division has just released its long-awaited revision of its 1996 clinical guidance for development of weight-loss drugs, and it provides specific guidance for companies like Sanofi-Aventis seeking to make metabolic syndrome claims.

For the past two years, Sanofi has focused all its presentations of clinical trial data for Acomplia on "metabolic syndrome," clearly believing insurers -- notoriously reluctant to pay for diet pills -- are more likely to cover a drug used to treat the cluster of conditions that increase the risk of cardiovascular disease and type 2 diabetes.

Now, the new guidance -- while not yet final -- suggests the FDA is taking a tougher view on drug applications seeking a "metabolic syndrome" indication. The latest draft of the guidance, posted on the agency website, states:

"The FDA does not necessarily consider the metabolic syndrome to represent a distinct disease entity. At present, there is no single etiological factor or central pathogenetic abnormality identified as mediating the constellation of excess visceral adiposity, abnormal lipids, elevated blood pressure, and insulin resistance that comprise the metabolic syndrome. Nonetheless, in addition to lifestyle modification, a host of drug therapies now exist to address individual or multiple components of the syndrome (e.g., lipid altering agents, antihypertensives, insulin sensitizers).

"Ideally, a therapeutic product intended to treat metabolic syndrome should normalize or improve all components of the syndrome, independent of weight loss (see section VIII), and ultimately be shown to prevent the development of type 2 diabetes and reduce cardiovascular morbidity and mortality."

This final sentence would appear to require demonstration in clinical trials that a drug improves each of the metabolic syndrome components and also improves cardiovascular morbidity and mortality independent of weight loss before the FDA will approve “metabolic syndrome” as an indication.

While Sanofi-Aventis has submitted a great deal of data relative to how Acomplia improves -- independent of weight loss -- some of the factors that contribute to metabolic syndrome, at this point the value of rimonabant in actually reducing cardiovascular morbidity and mortality is largely speculative.

Additional multi-year trials of Acomplia currently underway will be needed to demonstrate reduction of cardiocascular morbidity and mortality or prevention of the development of type 2 diabetes as endpoints.

While these new FDA guidelines were posted last week for 60 days of public comment and will not become official until finalized, they presumably shed light on current agency thinking relative to approval of the "metabolic syndrome: indication.

If this is accurate, many obese and overweight individuals hoping that the FDA will finally approve Acomplia for sale in the United States this summer had better start getting used to the idea that they probably are going to be spending their own money on the diet drug.