Most sexually active adults have been exposed to human papillomavirus (HPV), with as many as 20 million Americans estimated to be infected with the genital form. In most cases, it causes no health problems. But it does cause nearly all cases of cervical cancer the American Cancer Society (Atlanta) predicts 11,070 cases in 2008.

In an effort to address the market, Gen-Probe (San Diego) has launched a pivotal U.S. clinical trial of its investigational Aptima assay to detect HPV. There are currently four other tests that can detect HPV: Pap, ThinPrep Pap Test, Seeplex STD/HPV and Hybrid Capture II.

What would Gen-Probe have to offer that's different?

"If you think about the molecular diagnostics market, clearly the areas with the greatest commercial potential are chlamydia, gonorrhea, HIV, HPV and hepatitis," Gen-Probe's director of investor relations, Michael Watts, told Medical Device Daily. "It's an attractive and rapidly growing market and clearly we can make a difference."

The Aptima HPV assay is an amplified nucleic acid test that detects 14 high-risk HPV types that are associated with cervical cancer. It detects two messenger RNAs (mRNA), E6 and E7, that are made in higher amounts when HPV infections progress toward cervical cancer.

Watts said that targeting these mRNAs may more accurately identify women at higher risk of having, or developing, cervical cancer than competing assays that target HPV DNA.

Based on the technology, Watts said, "Gen-Probe's test would produce fewer false positive results."

Digene's (Gaithersburg, Maryland) HPV test, which uses the company's Hybrid Capture II technology, detects the presence of high-risk types of HPV, the cause of cervical cancer. It is both FDA-approved and CE-marked.

Seegene's (Rockville, Maryland) Seeplex is designed to screen for chlamydia, gonorrhea, 14 high-risk types of HPV and five low-risk types of HPV at the cost of a single pathogen test using a single sample (MDD, Nov. 12, 2007).

Despite the success of traditional Pap testing in reducing mortality from cervical cancer in the U.S., it does have limitations. One such limitation is poor sensitivity of individual Pap smears, which means the test misses cancers or precancerous changes.

HPV is spread by skin-to-skin contact with an HPV-infected area. Infections can be subclinical, meaning the virus lives in the skin without causing symptoms. This is why many people with HPV do not know they have it or that they could spread it. It can take weeks, months or years for genital warts to surface after sexual relations with an infected person.

Gen-Probe expects to enroll about 7,000 women in its study, although enrollment may vary based on the prevalence of cervical disease among women in the trial.

Women undergoing routine Pap testing at participating U.S. clinics are eligible to participate in the study, which includes two arms. One arm enrolls women whose Pap results are classified as atypical squamous cells of undetermined significance, meaning they are neither normal nor clearly indicative of changes associated with progression to cervical cancer. In these cases, HPV testing can help determine appropriate medical management.

The other arm enrolls women whose Pap results are normal. This arm will assess the ability of the Aptima HPV test to identify women who are at greater risk for cervical cancer.

The Aptima HPV assay is designed to run on Gen-Probe's fully automated, high-throughput Tigris instrument system, and on the company's current and future medium-throughput instrument platforms.

Gen-Probe said it remains on track to introduce the Aptima HPV assay as a CE-marked product in Europe in the second half of 2008.