Associated Press

WASHINGTON — Federal regulators said Friday that a GlaxoSmithKline vaccine prevents the leading cause of cervical cancer in women, bringing it a step closer to competing with Merck’s Gardasil, which has controlled the U.S. market for three years.

In documents posted online, the Food and Drug Administration said Cervarix — Glaxo’s vaccine against human papilloma virus or HPV — successfully blocked the two leading strains of the virus nearly 93 percent of the time.

But even as the British drugmaker, which has its U.S. headquarters in Durham’s Research Triangle Park, moves closer to competing in the U.S., Merck is poised to begin marketing Gardasil to boys and men. The FDA said that vaccine prevented genital warts in males 90 percent of the time.

The agency will ask a panel of vaccine experts next week to weigh in on both vaccines.

Leerink Swann analyst Seamus Fernandez said the benefit of Gardasil for boys likely will be minimal.

Genital warts caused by HPV usually clear up by themselves, and the cancers caused by the virus are extremely rare in men.

Glaxo has won a number of government contracts for Cervarix in Europe, but its U.S. launch was delayed in 2007 when the FDA said it needed more data about the vaccine. Earlier studies of Cervarix showed a higher number of muscular and neurological problems among patients who used the vaccine compared with an alternate treatment. The FDA said Friday that outside experts have now determined Cervarix did not cause those problems.

Glaxo wants its vaccine approved for girls and women ages 10 to 25.

Gardasil and Cervarix both defend against HPV strains 16 and 18, which cause about 70 percent of cervical cancer cases. But Merck’s vaccine also defends against two other HPV types that cause 90 percent of genital warts, something Cervarix does not target.