Merck & Co has been granted a six-month priority review of its candidate cervical cancer vaccine Gardasil in the USA, which could mean approval as early as June 8.

Gardasil protects against four strains of human papillomavirus (HPV) that account for an estimated 70% of cervical cancer cases and two types of virus that account for an estimated 90% of genital wart cases.

Along with partner Sanofi-Aventis which has rights to Gardasil in Europe, Merck is in a race with GlaxoSmithKline to bring the first HPV vaccine to market. GSK’s candidate, Cervarix, is due to be submitted for approval in Europe in the first half of 2006, followed by filings in other countries over the remainder of the year, so Merck could have several months’ lead in the important US market.

Analysts have suggested that Gardasil could quickly achieve sales of $500 million, rising to $3 billion at peak. If treated early, five-year survival rates for cervical cancer can be as high as 80%-90%, but they plummet to 14% if the cancer remains untreated and spreads, so demand for a vaccine is expected to be high.

Merck has also submitted marketing applications for Gardasil in the European Union and Australia, Mexico, Brazil, Argentina, Taiwan and Singapore.

Cervical cancer is the second most common cause of cancer death in women worldwide, resulting in a half-million diagnoses and approximately 300,000 deaths each year.