First large test shows vaccine prevents cervical cancer

TRENTON, N.J. -- The first large study of an experimental cervical cancer vaccine found it was 100 percent effective, in the short term, at blocking the most common cause of the disease, the vaccine's maker said Thursday.

Merck's genetically engineered vaccine prevents cervical cancer by blocking infection from the human papilloma virus strains that cause 70 percent of cervical cancers.

Other types of HPV, which is sexually transmitted, also can cause cervical cancer and painful genital warts. About 20 million Americans have some form of HPV.

Testing the vaccine

The final-stage study of the vaccine included 10,559 sexually active women ages 16 to 26 in the United States and 12 other countries who were not infected with the HPV strains 16 or 18. Half got three vaccine doses over six months; half got dummy shots.

Among those still virus-free after the six months, none who received the vaccine developed either cervical cancer or precancerous lesions likely to turn cancerous over an average two years of follow-up, compared with 21 who got dummy shots.

"To have 100 percent efficacy is something that you have very rarely," said Dr. Eliav Barr, Merck's head of clinical development for the vaccine called Gardasil. "We're breaking out the champagne."

Merck shares rose 56 cents, or 2.1 percent, to $27.45.

The study, which was funded by Merck, is to be presented today at a meeting of the Infectious Diseases Society of America.

A second analysis, including hundreds more women participating in the ongoing study, showed that after just one dose the vaccine was 97 percent effective. That analysis found only one of the 5,736 women who got the vaccine developed cervical cancer or precancerous lesions, compared with 36 among the 5,766 who got dummy shots.

Barr said the 97 percent rate was more "real world," given that patients sometimes miss or delay follow-up shots or tests.

'Phenomenal breakthrough'

"I see this as a phenomenal breakthrough," said Dr. Gloria Bachmann, director of The Women's Health Institute at Robert Wood Johnson Medical School in New Brunswick.

Bachmann said diagnosis of infection leaves women anxious over the heightened risk of cervical cancer and raises questions among couples about infidelity and prior sexual activity.

"You have to get students in grammar school, middle school, high school (vaccinated) before they become sexually active," she said.

Cervical cancer is the second-most common cancer in women and their No. 2 cause of cancer deaths, resulting in about 3,000 deaths in the United States and nearly 300,000 around the world each year. At least half of sexually active men and women become infected with genital HPV at some point.

The immune system clears most such infections in a year or two, but several types of HPV can persist, cause cervical cancer or trigger other cancers in the genital area. There is no cure for HPV, but the cancers can be treated and an improved Pap test is catching more cervical cancer before it has spread.

Whitehouse Station-based Merck, hammered by slumping revenues and profits and facing roughly 5,000 lawsuits over its withdrawn painkiller Vioxx, is seeking to beat rival drug maker GlaxoSmithKline PLC to market with the first cervical cancer vaccine.

GlaxoSmithKline is still enrolling patients in final-stage tests to determine whether its vaccine prevents cancer, but expects to have initial data by late next year.

Spokeswoman Danielle Halstrom said earlier research showed it blocks infection with two virus strains 100 percent. The Merck vaccine also reduces infection with two other HPV strains that cause 90 percent of genital warts cases.

Merck plans by year's end to seek Food and Drug Administration approval to sell its vaccine for use by girls and young women.

"If all goes well, sometime in 2006 it should be on the market," Barr said.

Merck is continuing research on Gardasil and will soon report on four years of follow-up on women in the current study. The company also will explore whether the vaccine's effectiveness wanes over time. Barr noted that some women in the study developed dangerous precancerous lesions caused by HPV types other than 16 and 18.