Concerns over the safety of diet drug Acomplia (rimonabant) seem likely to continue until the diet pill has been on the market for some time, according to a research update issued May 18th by an analyst for Morgan Stanley.

The investment banking firm said some scientists have pointed out that data presented at a recent symposium had shown that patients treated with Acomplia in some of the clinical trials of the drug experienced less "joy" than patients on placebo.

This report, while short on details, certainly adds to concerns about this novel drug that affects receptors in the brain. Earlier comments have focused on the 2.7-fold higher rate of psychiatric disorders reported in clinical trials among those receiving Acomplia vs. the placebo.

While Sanofi is not expected to receive formal approval to start marketing the drug in Europe for another six weeks, a key committee of the European Medicines Agency (EMEA), the Committee for Medicinal Products for Human Use (CMPH), recommended approval of the drug on April 28th.

More than 95 percent of CHMP recommendations lead to EMEA marketing authorizations in just over two months.

But even if Acomplia makes it to market in Europe this summer, it seems increasingly likely that no Acomplia sales will take place in the United States this year.

It has been almost three months since the U.S. Food and Drug Administration sent Sanofi an "approvable" letter, delaying action on approval of Acomplia pending resolution of undisclosed issues.

Sanofi has stonewalled all questions as to the nature of these issues or their seriousness, but as time passes, speculation increases that the FDA continues to have safety concerns about Acomplia.

If that is the case, many observers think it highly unlikely that an FDA under attack for not paying sufficient attention to safety issues will act on Acomplia without first having the pros and cons of this treatment debated by the independent experts on one of its advisory committees.