As expected the US Food and Drug Administration has opened the door to Merck & Co's Gardasil vaccine for the prevention of anal cancer anal intraepithelial neoplasia.

The US regulator followed the recommendation of its advisors last month by approving the drug for the prevention of anal cancer caused by human papillomavirus (HPV) types 16 and 18 and for the prevention of anal intraepithelial neoplasia grades 1, 2 and 3 (anal dysplasias and precancerous lesions) caused by HPV types 6, 11, 16 and 18, in males and females nine through 26 years of age.

The group's US filing included data from a Phase III trial, first revealed back in February, which showed that Gardasil was able to prevent 77.5% of HPV 6, 11, 16, and 18-related AIN and anal cancer, clearly demonstrating its potential protective power for patients.

“Treatment for anal cancer is challenging; the use of Gardasil as a method of prevention is important as it may result in fewer diagnoses and the subsequent surgery, radiation or chemotherapy that individuals need to endure,” said Karen Midthun, director of the FDA’s Center for Biologics Evaluation and Research, commenting on the FDA's decision.

Anal cancer is relatively uncommon, affecting around 2,000 men and more than 3,000 women in the US every year, but the vast majority - up to 90% of cases - are caused by the HPV virus, with the subtypes 16 and 18 collectively responsible for about 80% of these. However, while the market is not huge, it is growing, and Gardasil’s sales, which came in at $316 million in the last quarter, will undoubtedly receive a boost from its expanded indication, potentially giving the vaccine a competitive edge over GlaxoSmithKline’s rival cervical jab Cervarix.

According to Merck, Gardasil is the only HPV vaccine approved for use in both men and women. The product already on the market for use in girls and young women for the prevention of cervical, vulvar and vaginal cancers caused by HPV types 16 and 18, genital warts caused by HPV types 6 and 11, and precancerous or dysplastic lesions caused by HPV types 6, 11, 16 and 18. In addition, the jab is also approved for use in males aged nine to 26 years of age for the prevention of genital warts caused by HPV types 6 and 11.