Sanofi's Prospects Get Leaner

Shares of Sanofi-Aventis (SNY Quote) skidded Thursday, one day after the company suffered a major setback for its weight-loss drug Zimulti.

A panel of outside advisers to the Food and Drug Administration recommended unanimously Wednesday that the agency reject the obesity drug because Zimulti's risks were greater than its potential benefits of reducing weight in obese patients.

The medical experts said the company had failed to provide enough proof in its clinical trials about the drug's safety, especially its risk of triggering suicidal thinking.

At least four analysts cut their ratings on the French drug giant. Shares were off $1.33, or 3.1%, to $41.74, and the stock fell as low as $41.09. Volume was much heavier than normal.

The FDA is expected to rule in late July on Zimulti, which is sold in foreign markets under the trade name Acomplia. The FDA isn't required to follow advisory committee recommendations, but it usually does. The panel's unanimous opposition seems to leave little room for Zimulti's immediate endorsement.

"Approval [is] unlikely until the next decade at the earliest," says Alexandra Hauber, of Bear Stearns, in a research note. Hauber reaffirmed the underperform rating that she has had since October.

She doesn't own shares, but her firm has had a noninvestment banking relationship.

Hauber removed potential U.S. Zimulti sales from her economic model through 2012, but she kept her foreign-market sales intact.