British drugmaker GlaxoSmithKline said Friday U.S. regulators approved its vaccine Cervarix to prevent the leading cause of cervical cancer in women.
The approval from the Food and Drug Administration allows Glaxo to compete against Merck's blockbuster vaccine Gardasil, which has been on the market here since 2006.
London-based Glaxo said it expects to launch the vaccine late this year.
Cervarix already is approved in nearly 100 other countries, but had been delayed in the U.S. since 2007, when the FDA requested additional data from the company.
The vaccine blocks human papilloma virus strains 16 and 18, the two types of HPV that cause 75 percent of cervical cancers. Additionally, Glaxo said the vaccine is also highly effective against strain 31, which is the third most common HPV type that causes cancer.
There are more than 100 types of HPV, though about 15 are known to cause cervical cancer.
Cervarix's effectiveness against extra strains of the virus could help differentiate it Merck's Gardasil, which also protects against HPV 16 and 18, but not other cancerous strains.
Still, Glaxo is likely to face an uphill battle in the U.S. Besides an established brand, Merck's vaccine also defends against two other HPV types that cause 90 percent of genital warts, which Cervarix does not target.
Gardasil became an early success story for Merck after its 2006 launch, achieving sales that are rare for a vaccine. The Whitehouse Station, N.J., company has sold about 50 million doses worldwide, with more than $1.4 billion in revenue last year.
But sales have been slowing amid questions about the longevity of the vaccine's effect and its price tag of nearly $400.
Glaxo has not yet discussed pricing for its vaccine.
Side effects with Cervarix were mostly mild, including pain and swelling at the injection site, fatigue and headache.
HPV infects about 6 million people in the U.S. each year, and is spread mainly through sexual contact. It usually causes no symptoms and goes away within two years, although rare cases can develop into warts and cancer in both men and women.
Last year, nearly 4,000 women died of cervical cancer in the U.S., less than 1 percent of all deaths from cancer.
U.S.-listed shares of GlaxoSmithKline PLC fell 14 cents to $41.14 in afternoon trading.