After placing an ad in the Washington Post and staging rallies in front of the Capitol and the FDA's headquarters, activists angry at the agency's decision to withhold approval for the prostate cancer drug Provenge have found a new way to voice their discontent.

Starting today, 25 Washington Metropolitan Area Transit buses will carry an ad headlined "Provenge Confidential." The month-long campaign, styled as a poster for a film noir, is sponsored by CareToLive, a group that has sued the FDA for allegedly conspiring against the prostate cancer drug, developed by Seattle-based Dendreon. CareToLive is composed of patient activists as well as investors caught on the wrong side of Dendreon shares' roller-coaster ride.

The ads make reference to "Machiavellian power grabs" and "undisclosed conflicts of interest" that supposedly led the FDA to request more data from Dendreon instead of approving it last May. An agency advisory panel had voted in favor of the drug.

The ads look like this:

Other investors blame the company instead, claiming it didn't communicate Provenge's real chances of getting approved. The Securities and Exchange Commission has started an informal inquiry on the issue.