Vaccine blocks cancer cause

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A trial involving more than 12,000 women from 13 countries has found an experimental vaccine "100 percent effective" in blocking a sexually transmitted virus that is the most common cause of cervical cancer, the vaccine's maker announced yesterday.

The achievement was timely for New Jersey-based pharmaceutical firm Merck & Co., which has been hammered by slumping revenues and profits and is facing thousands of lawsuits since it voluntarily withdrew its painkiller, Vioxx, because of safety concerns.

In a study that followed women for an average of two years, Merck's genetically engineered vaccine, Gardasil, prevented infection from human papilloma virus (HPV) strains 16 and 18 in all women who received the inoculation. Those two HPV strains cause 70 percent of cervical cancers.

Study participants were sexually active women between 16 and 26 who were not infected with HPV strains 16 and 18 at the start of the study. Half of the women in the study received three doses of Gardasil over six months. The other half were administered a dummy shot.

By the end of the research, no cases of cervical cancer or precancerous lesions were observed among the vaccinated women, compared with 21 cases in the placebo group.

"This is a breakthrough. ... These results tell us we should be using this vaccine as a preventive," said Dr. Lorna Rodriguez, chief of gynecologic oncology at the Cancer Institute of New Jersey.

"Clearly, this is a very important advance ... since it will reduce the burden of cervical cancer significantly both here and abroad," at least "for the short term," said Dr. Allan Hildesheim , an epidemiologist with the National Cancer Institute in Bethesda.

Results of the vaccine trial, financed by Merck, will be presented today at a meeting of the Infectious Diseases Society of America in San Francisco.

Investigators also will present results of a secondary analysis, which was broader in scope and showed that after just one dose of Gardasil, only one of the 5,736 women who received the vaccine developed cervical cancer -- or precancerous lesions that are likely to become malignant -- over two years of follow-up.

In contrast, 36 of the 5,760 women who received a dummy shot got cervical cancer or precancerous lesions.

"These are the first pivotal data to show that vaccination with Gardasil reduced HPV 16- and 18-related cervical precancer and noninvasive cervical cancer," said lead investigator Laura Koutsky of the University of Washington at Seattle.

"These results are huge," said Merck spokeswoman Kim Metcalf, who stressed how rare it is to get such high efficacy rates in clinical trials.

No women were stopped from continuing in the studies "due to serious vaccine-related adverse events," the company said. The most common complication reported was discomfort at the injection site.

According to the federal Centers for Disease Control and Prevention, an estimated 10,000 new cases of cervical cancer will be diagnosed in the United States this year, and nearly 4,000 women will die of the disease.

Worldwide, cervical cancer kills as many as 300,000 women annually. It remains the leading cause of cancer deaths in women in parts of the world where Pap tests are not available.

About 20 million American men and women are infected with HPV. The virus also has been identified as the cause of genital warts, a sexually transmitted disease, and of abnormal Pap smear results.

In addition to HPV types 16 and 18, Gardasil was designed to target types 6 and 11, which are responsible for 90 percent of genital warts cases. These four HPVs also are blamed for causing benign cervical changes that result in abnormal Pap tests.

Merck has been in a race with another pharmaceutical giant, GlaxoSmithKline, to get approval from the Food and Drug Administration for an effective HPV vaccine.

Merck said that before the end of the year, it plans to seek FDA approval to sell the vaccine.