FDA Holds Up Wyeth Drug

However, sales have slowed, gaining 3% year over year in the second quarter but declining 3% during the first half of 2007 compared with the same period last year.

Accompanying this has been a growing number of lawsuits alleging that the drugs raise the risk of breast cancer, ovarian cancer, stroke or heart damage. As of March 31, Wyeth was a defendant in 5,200 personal injury cases in the U.S.

Unlike Premarin and Prempro, Pristiq isn't a hormone-based drug. In fact, it's the first nonhormone treatment for hot flashes and other symptoms of menopause.

The drug's main ingredient, desvenlafaxine succinate, is the same as that in the experimental depression drug also called Pristiq. The key ingredient is related to the ingredient in the antidepressants Effexor and Effexor XR, Wyeth's bestsellers during the second quarter.

Wyeth has discussed Pristiq as a successor to Effexor XR, whose U.S. patent protection expires in June 2010 and which will begin facing generics in Europe in late 2008. The older Effexor already has lost U.S. patent protection.

"This blow to Pristiq will intensify the company's exposure to Effexor [XR] generics in 2010," Ryan warns.

At one point in its development, Pristiq's depression indication appeared to be the closest for marketing, but Wyeth has pulled back on its timetable. The FDA granted conditional approval in January for Pristiq as an antidepressant, and the agency said it didn't need extra clinical trials.

Wyeth has said it wants to test Pristiq at a lower dose before amending its depression application to the FDA. Test results for the lower-dose version will be sent to the FDA next month, and Wyeth executives said last week that they expect the agency to extend its review into the first quarter of 2008.

Merrill Lynch's Risinger said he worries that Pristiq's launch as an antidepressant could be delayed until early 2010, too.