The Government Accountability Office (GAO) released a report Monday which evaluated the FDA's follow-up of drugs approved through its accelerated approval process, and it noted among its findings that some of these drugs remain on the market even though no post-marketing evidence has been produced to show a clinical benefit.

In its report, GAO noted that 144 confirmatory post-marketing studies were required by the FDA for the 90 drug applications that were approved by the accelerated process between 1992 and November 2008. Of the 144 studies, 64 percent have been closed, while "several of the remaining studies have been classified by FDA as open for an extended period."

The investigator also found that the agency has never acted on its authority to expedite the withdrawal of any of these drugs from the market if a required confirmatory study was not completed, or if a study failed to confirm a clinical benefit. The investigator explained that "weaknesses in [the] FDA's monitoring and enforcement process hamper its ability to effectively oversee post-marketing studies."

GAO recommended that the FDA "clarify the conditions under which it would utilise its authority to expedite the withdrawal of drugs under its accelerated approval process."

In response, FDA officials explained that given the unique circumstances of individual drugs, it would be "difficult, if not impossible" to draft a standard policy for withdrawals. The regulator, which indicated it has taken steps to improve its oversight, said that withdrawing a product would sometimes mean eliminating the only available treatment for a condition.