UPDATE 3-US FDA panel backs Glaxo cervical cancer vaccine

* FDA advisers say Cervarix safe, effective

* Panel backs Merck vaccine to prevent warts in males

* Glaxo shares gain 0.5 pct, Merck shares gain 1.9 pct (Recasts; Adds vote on Merck vaccine; updates shares)

GAITHERSBURG, Md., Sept 9 (Reuters) - GlaxoSmithKline PLC GSK.L won a U.S. panel's support on Wednesday for a cervical cancer vaccine, moving the company closer to competing in the United States with a rival vaccine from Merck & Co. MRK.N

The panel also supported allowing Merck to widen the potential market for its vaccine by promoting it for men and boys as young as 9 for prevention of genital warts.

Both Glaxo’s Cervarix and Merck’s Gardasil protect against infection with the sexually transmitted human papillomavirus (HPV), which causes cervical cancer and genital warts.

Food and Drug Administration advisers, in an 11-1 vote, said Cervarix appeared safe despite miscarriages reported around the time of vaccination and a small number of autoimmune problems such as rheumatoid arthritis and lupus. Panelists urged monitoring for those issues after approval to see if there was any link to the vaccine.

“The data we have seen to date are reassuring” on autoimmune conditions, said Dr. Lisa Rider, a panel member and official at the National Institutes of Health, adding “I think we do need very strong post-marketing studies.”

The committee voted 12-1 that Cervarix was effective for girls and young women ages 10 to 25.

The FDA usually follows panel recommendations. Glaxo said a final decision on Cervarix may come as early as this month.

The vaccine already is approved in 98 countries, but some analysts say it will be hard for Glaxo to compete against Gardasil’s three-year headstart in the U.S. market. Gardasil won FDA clearance in 2006, while the launch of Cervarix was stalled after the FDA asked for more information following Glaxo’s initial application in 2007.

The delays mean Cervarix is no longer the mega blockbuster hope it once was, although FDA approval could still be a minor positive catalyst for Glaxo shares, Citigroup analysts said.

Four years ago, previous Chief Executive Jean-Pierre Garnier touted the vaccine as Glaxo’s most important new product. But the British drugmaker missed the opportunity to vaccinate the initial group of eligible teenage girls in the United States, ceding that business to Gardasil.

Consensus forecasts ahead of the panel decision suggest Cervarix will generate worldwide sales of about $1.2 billion in 2013, equivalent to some 2.5 percent of expected Glaxo sales for that year, according to Thomson Reuters I/B/E/S.

Cervical cancer is often caught early in the United States through Pap smears while the disease is treatable. Still, about 4,000 U.S. women die each year from the disease. Worldwide deaths from the disease total about 280,000, mostly in developing countries where screening is lacking.

“If approved, Cervarix will help provide protection against cervical cancer, a devastating disease that is responsible for thousands of deaths in U.S. women each year,” said Barbara Howe, director of Glaxo’s North American vaccine development.

The company promised to track complications and miscarriages after approval. Neither Cervarix nor Gardasil is recommended for pregnant women. Glaxo officials said there was no evidence Cervarix caused autoimmune diseases or miscarriages.

Gardasil has generated controversy over potential side effects as well as the cost of about $360 for preventing a disease that is treatable if caught early.

The FDA and Centers for Disease Control and Prevention say Gardasil remains safe with no unusual complications, and problems such fainting and nausea remain rare.

The advisory panel voted 7-1 that Gardasil was safe for males ages 9 to 26. Vicky Debold, the panel’s consumer representative, said more study of safety was needed given complaints from parents about health problems in females.

“We need to figure this out before we subject boys to a risk that is not necessary at this point,” she said.

Merck said it was pleased with the panel decision and expected an FDA ruling on male use this fall. Global sales of Gardasil topped $1.2 billion in 2008.

Both vaccines fight two HPV strains that cause about 70 percent of cervical cancers. Gardasil also targets two other HPV strains that cause genital warts. It is unclear how long protection lasts or if booster shots will be needed.

HPV also can cause penile and anal cancers, although both are rare.

Glaxo shares rose 0.5 percent to $39.22 on the New York Stock Exchange, while Merck shares gained 1.9 percent to $31.55 on the NYSE. (Reporting by Lisa Richwine and Ben Hirschler; Editing by Gary Hill and Carol Bishopric)