Prospects of U.S. Food and Drug Administration action in 2006 on diet drug Acomplia (rimonabant) dimmed considerably with news that the Endocrinologic and Metabolic Drugs Advisory Committee -- which had been tentatively planning to meet in November -- now has no plans to meet untll next year.

Most observers believe the FDA, which more than three months ago set out for Sanofi-Aventis in an "approvable" letter issues that need to be resolved prior to approval for weight management, will not act until the high-profile diet pill is thoroughly vetted by an advisory panel of independent outside experts.

Given that Acomplia is first in a new class of drugs that interferes with receptors in the brain that help regulate appetite, most find it hard to imagine the FDA will move forward before outside experts weigh in -- particularly in light of trial side effects that included a 2.7-fold higher rate of psychiatric disorders.

In the latest update of the 2006 tentative meeting schedule for the FDA's Endocrinologic and Metabolic Drugs Advisory Committee, plans to convene that panel Nov. 8-9 now have been replaced by the message "to be announced if needed." The November dates would become the third abandoned meeting of the year for the panel.

A spokesperson for the FDA panel confirmed on May 24th that no further meetings of the advisory committee are even tentatively scheduled for this year at this time.

While a session of the advisory panel to consider Acomplia could be convened on relatively short notice (only a 15-day advance notice published in the Federal Register is required), the removal of the November meeting from the tentative schedule would appear to auger poorly for Sanofi.

The French pharmaceutical company continues to decline to shed any light on the nature or seriousness of the issues that it needs to work out with the FDA prior to action by the agency on approval of Acomplia, but three months with no word of progress -- or word of any kind -- is not a good omen.

If the issues were minor, most observers believe Sanofi long since would have made them public.

The U.S. delays also focus even more attention on the European Medicines Agency (EMEA), which is widely expected to act in early July to authorize sale of Acomplia in European Union countries. Sanofi has already identified Britain and Germany as countries where it hopes to launch Acomplia in July.

A key committee of EMEA, the Committee for Medicinal Products for Human Use (CMPH), on April 28th recommended approval of Acomplia as an aid to weight-loss, and more than 95 percent of CHMP recommendations lead to EMEA marketing authorizations in just over two months.

But as the 95 percent figure suggests, EMEA approval following a CHMP recommendation is not automatic -- and given the puzzling history of optimistic Sanofi pronouncements related to FDA approval followed by delay and mystery, the fate of the diet drug with the EMEA is being closely watched.