The unanimous, 13-0, vote by a panel of cancer experts recommending the agency reject Abbott's Xinlay came after an FDA staff report said the North Chicago-based company's studies thus far have not been statistically significant enough to merit the advisory panel's endorsement. The FDA, which is expected to consider Tuesday's vote on Xinlay in October, often follows the recommendation of its panels.

Many drug industry observers were watching Abbott's submission because it used data that said that, statistically, the drug did not show effectiveness in two clinical trials. A submission based on that type of data was considered a bit of a gamble in the wake of Vioxx controversies. The FDA approved Vioxx in 1999, but the drug was pulled by its maker last fall after a study showed increased risks of heart attacks and strokes.

Statistical Significance

FDA staff and panel members said Abbott needs to do more work to prove its effectiveness and show a clearer benefit. Abbott said it has studies in the works that should address the panel's concerns, but will wait until the FDA provides more guidance for the company in October.

"You can't talk about the clinical significance of the data if you don't have statistical significance," said Ralph D'Agostin, a Boston University statistician serving on the panel at the meeting in Bethesda, Md.

Abbott was hoping to plug Xinlay into a looming void in its drug pipeline with key brand names facing more competition from rivals and possibly cheaper generics in the coming years. Now analysts say Xinlay -- a drug some say could eventually generate $1 billion or more in annual sales -- is at least two years from reaching the market if it eventually wins approval.

Abbott had held out hope the committee would see the drug's benefits in prostate-cancer patients who are nearing the end of their lives and have no other hope.

Delayed Onset of Excruciating Pain

It's common for cancer drugs to be approved by the FDA even if they show they can slow the spread of the disease in a small number of people. Cancer patients and their advocates used that argument in backing Abbott's submission of Xinlay to the FDA panel.

Furthermore, Abbott researchers pushed the aspect that the drug delayed the onset of excruciating pain, a common occurrence as prostate cancer reaches the bone.

"Despite the vote, it was a positive discussion and helpful to us," said Dr. Eugene Sun, vice president, global pharmaceutical clinical development at Abbott. "The level of statistical certainty was the dominant issue."

The FDA said recent scrutiny of its approval process had nothing to do with the panel's decision to deny Abbott's application. "We have not had a change in policy in regard to review of oncology drugs," an FDA spokeswoman said.

Panel members and the FDA staff said Xinlay showed "activity" in patients and encouraged Abbott to bring the drug back once more studies can be done.

'Drug Has Clinical Benefit'

Abbott said it has a large study, known as "244" of about 1,000 men it expects to complete early next year. That clinical trial involves patients taking Xinlay who have failed hormone therapies and have not yet had cancer spread beyond the prostate.

"The drug has clinical benefit, and they acknowledge the drug is clearly doing something," Sun said of the panel's feedback.

Some on Wall Street think Abbott will be under more pressure should Xinlay not reach the market in 2007. Abbott's antibiotic Biaxin and thyroid drug Synthroid are losing sales to generic versions while a similar fate awaits the bipolar disorder drug, Depakote, in 2008 when it is scheduled to lose patent protection. Depakote is on pace to generate $1 billion in US sales this year.