NEW YORK (Reuters) - An experimental Merck & Co. vaccine completely prevented early-stage cervical cancer and precancerous cervical lesions caused by the two most common forms of a virus linked to such cancers, Merck said on Thursday.
"This trial confirms that a vaccine can give young women a high level of protection from developing precancerous lesions and early cervical cancers," Laura Koutsky, a professor of epidemiology at the University of Washington who led the study, told Reuters.
Shares of U.S. drugmaker rose 1.3 percent in afternoon trade.
The favorable findings were seen in a late-stage trial sponsored by the U.S. drugmaker, which included more than 12,000 women from 13 countries, aged 16 to 26, who were not infected with either of the virus types when the trial began.
The two forms of human papillomavirus, types 16 and 18, are responsible for an estimated 70 percent of cervical cancer cases, and are the targets of Merck's Gardasil vaccine. Such cancers kill about 300,000 women worldwide each year, including almost 4,000 in the United States, Merck said.
Merck, whose earnings plunged after the withdrawal last year of its Vioxx arthritis drug, plans to seek U.S. approval for the cancer vaccine, which also protects against genital warts. Merck is partnering its vaccine in Europe with Sanofi-Aventis.
Half the women in the Phase III trial received three doses of Gardasil over a six-month period, while the other women received placebos. The women were then followed for an average of 17 months.
Merck said Gardasil was 100 percent effective in preventing precancerous lesions and early-stage cancers associated with virus types 16 and 18 among women who remained free of infection until they received their final dose of the vaccine. The vaccine thereby easily met its primary trial goal.
By contrast there were 21 cases of lesions and early-stage cancers associated with the two virus types among those taking placebos, Merck said.
Although the vaccine was completely protective against the two virus types, Koutsky said she hoped the vaccine will eventually be improved to protect against up to another half dozen types of the virus that cause cervical cancer.
"In that case, you could be blocking viruses that cause 87 percent of cervical cancer cases, instead of 70 percent," she said.
Industry analysts have said Gardasil could generate peak annual sales of over $2 billion that could help revive fortunes of Merck. The company based in Whitehouse Station, New Jersey, is facing thousands of lawsuits from former Vioxx users and their families, who claim the withdrawn drug caused heart attacks and other serious health problems.
Gardasil is slated to compete with GlaxoSmithKline Plc's experimental Cervarix cervical cancer vaccine, which targets the same two cancer-causing virus types, but is expected to be approved later than the Merck product. Glaxo's U.S. partner on its vaccine, which does not protect against genital warts, is MedImmune Inc..
In separate earlier-stage trials, Glaxo's vaccine seemed to have more impressive data than Gardasil by proving 100 percent effective in blocking infections with human papillomavirus types 16 and 18. Gardasil was shown to be 90 to 95 percent effective.
Glaxo, in highlighting its seemingly better results, said its vaccine uses a novel adjuvant, or additive, to give a faster, stronger and longer immune response than conventional adjuvants.
Scott Henry, an analyst with Oppenheimer & Co., said Thursday's impressive data for Gardasil are not a big surprise, given favorable results in earlier trials. "So there's no real change in thinking about Merck's vaccine."
But Henry cautioned the Merck and Glaxo vaccines could both fail to meet optimistic sales projections unless government health agencies require that they be given to young girls -- and possibly to young boys, to prevent them from eventually contracting and spreading the viruses.
Shares of Merck were up 35 cents, or 1.3 percent, to $27.24, on the New York Stock Exchange. They had risen as much as 5.6 percent in pre-market electronic trading. Glaxo shares rose 52 cents, or 1 percent, to $51.47, also on the NYSE.
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