US panel positive on Merck vaccine for anal cancer

* Vaccine already approved to prevent cervical cancer

* FDA considering approval for anal cancer in men, women

* Gardasil sales have stalled amid competition

SILVER SPRING, Md., Nov 17 (Reuters) - Merck & Co's MRK.N Gardasil vaccine appears effective for preventing anal cancer, members of a U.S. advisory panel said on Wednesday.

The Food and Drug Administration advisers did not take any votes on the the product, but most said Gardasil was shown effective in company studies.

“I do think the data are sufficiently strong,” said panel Chairman Jose Romero, a pediatric infectious disease expert at Arkansas Children’s Hospital.

Merck presented data testing the vaccine in men, but many panelists said they felt confident that Gardasil also would protect women from anal cancer.

The FDA will consider the panel’s input as it decides whether to approve Gardasil for vaccinating males and females ages 9 through 26 for preventing anal cancer.

Gardasil already is sold for girls and young women to prevent cervical cancer and to prevent genital warts in boys and men. The vaccine fights infection with the sexually transmitted human papillomavirus (HPV), best known as the primary cause of cervical cancer. HPV also can lead to cancers of the anus, penis, head and neck.

The vaccine was once seen as a potential monster seller for Merck, but sales have stalled amid competition from a rival GlaxoSmithKline GSK.LGSK.N product and because many younger women already have been immunized with Gardasil, limiting the market size. The vaccine's sales hit $1.1 billion worldwide in 2009.

An FDA ruling is expected by year end on Gardasil’s use for preventing anal cancer, and for preventing cervical cancer in women ages 27 to 45, Merck spokeswoman Pam Eisele said.

Shares of Merck, which released positive data on an experimental heart drug earlier on Wednesday, were trading up 1.6 percent at $34.65 on the New York Stock Exchange. (Reporting by Lisa Richwine. Editing by Robert MacMillan)