The shareholders' suit -- filed this week in the United States District Court for the Western District of Washington -- alleges Dendreon failed to disclose and misrepresented "material adverse facts" relating to approval of Provenge by the Food and Drug Administration.

Specifically, the complaint charges the company exaggerated the significance of the results of Provenge's clinical studies, when in fact, the findings "were abbreviated and insufficient for FDA approval."

Late last month, the FDA told Dendreon it would still need either a positive interim or final analysis of survival data from the company's ongoing IMPACT study of Provenge in order to grant full approval to the groundbreaking vaccine. Dendreon said it expects to have the extra data by 2008.

But the suit alleges that Dendreon had told investors that it would have an approval decision from the FDA by mid-May 2007. Yet on May 9, "the company shocked investors" by revealing that the agency needed more data before clearing the vaccine for market, the complaint charges.

The lawsuit was filed by the New York-based law firm Dreier LLP on behalf of all purchasers of Dendreon common stock on or before July 24, 2007.