CORRECTED-UPDATE 2-US advisers reject Glaxo,Merck prostate drugs

(Corrects fourth paragraph to clarify that the vote went against Glaxo's Avodart, not Merck's Proscar)

* Both drugs already approved for enlarged prostate use

* Glaxo seeks wider approval, Merck data up for review

* Panel says risk of serious cancers a top concern

* Glaxo disappointed, both companies to work with FDA

* FDA to weigh panel votes, make final decisions (Adds comments from FDA panel, companies)

By Susan Heavey

WASHINGTON, Dec 1 (Reuters) - U.S. advisors recommended against wider use of two prostate drugs by GlaxoSmithKline Plc (GSK.L)(GSK.N) and Merck & Co Inc (MRK.N), saying they could raise the risk of more serious cancers even though they appeared to reduce the risk of less serious prostate tumors.

A Food and Drug Administration advisory panel said they did not see a benefit in exposing men to drugs that may ultimately lead to more, possibly deadly cancers being missed. They also questioned the companies' lack of long-term data on patients.

"For the patient who is worried about dying from prostate cancer, treatment with (such drugs) is the last thing he should do," Dr. Patrick Walsh, a urologist at Johns Hopkins Medical Institutions and a guest speaker, told panelists.

FDA's advisers agreed, voting near unanimously to reject Merck's Proscar and 14-2 against Glaxo's Avodart.

Panel chairman Dr. Wyndham Wilson, a senior investigator at the National Cancer Institute's Center for Cancer Research, said the greater risk of more serious cancers with the drugs was "unequivocal" and showed they "may simply be delaying diagnosis of the higher grade disease -- and that is the last thing we want to do."

Glaxo is seeking FDA permission to more widely market its drug to men at greater risk of developing prostate cancer. Merck, which is not seeking such an expansion, could include data from a recent trial involving healthy men on the label for its drug if the FDA approves.

Both drugs are already approved to treat symptoms of an enlarged prostate, the gland in males that helps produce seminal fluid. FDA will weigh the panel's recommendation before making its final decisions.

Glaxo representatives told panelists their data showed a favorable benefit in using Avodart in men who have high prostate-specific antigen (PSA) test results who have also undergone a biopsy that turned out to be negative.

"This represents an important medical need," Anne Phillips, a Glaxo vice president, told the panel. Glaxo "is not proposing that dutasteride (Avodart) be used for every man over 50 with a rising PSA. We are proposing to proceed carefully."

PSA tests are controversial because they do not show which men have low-risk, slow-growing cancers and which men need immediate treatment. As a result, many men live with side effects from treatment for a cancer that would never harm them.

But FDA staff expressed numerous concerns about both companies' data, including the number of men needed to see any results, questions about the men studied, and a clear increase in men who had higher grade cancer after taking the drugs.

According to the National Cancer Institute, about 218,000 U.S. men will be diagnosed with prostate cancer in 2010. Treatments include chemotherapy, surgery and hormonal therapies.

In a statement after the meeting, Glaxo said it was disappointed in the panel's vote. It expects a final FDA decision by Jan. 26.

Merck, which has said it participated in the meeting at the FDA's request and is not seeking a new formal indication for Proscar, said after the meeting that it would work with the FDA to continue to weigh the findings presented by the company from a government-funded trial. (Reporting by Susan Heavey; additional reporting by Julie Steenhuysen in Chicago; editing by Tim Dobbyn and Andre Grenon)