Gen-Probe Incorporated announced that the Company's West Nile virus (WNV) assay is now available for use by blood centers in the U.S. to begin clinical testing of the virus in freshly donated human blood. Within weeks, approximately 80% of the U.S. blood supply will be screened using the Gen-Probe assay. Gen-Probe's nucleic acid blood screening test for the detection of WNV, which will be distributed by Chiron Corporation, is the first such test to prospectively screen the U.S. blood supply under an IND. The prospective protocol was accepted by the FDA on May 16, 2003. Gen-Probe's assay was previously used to test retrospective, archived samples collected during last summer's peak mosquito season to help establish disease prevalence.

"This represents a significant milestone for Gen-Probe and the National Heart, Lung, and Blood Institute, who were jointly committed to having a WNV blood screening test available in time for the 2003 mosquito season," said Henry L. Nordhoff, chairman, president and chief executive officer of Gen-Probe. "We are pleased to announce that we have shipped the assay and testing will start ahead of schedule. Once again, Gen-Probe has proven its ability to quickly develop and implement rapid and accurate tests to improve human health."

When FDA study requirements have been met, Gen-Probe will submit a Biologics License Application (BLA) to the FDA to permit commercial sales of the product. Until licensure, Gen-Probe expects to recover its costs on tests that are delivered to customers. This cost recovery will be recorded as collaborative research revenues.

As of the end of 2002, the Centers for Disease Control and Prevention (CDC) reported 4,156 cases of WNV in the U.S. with 284 deaths. In a small number of cases, transmission is believed to have occurred by transplanted organs or blood transfusion.

The WNV assay was developed using Gen-Probe's family of technologies, including a unique nucleic acid amplification technique called Transcription-Mediated Amplification (TMA). Researchers have demonstrated that TMA technology can improve the safety of the blood supply by directly detecting and amplifying viral nucleic acids in the test tube. This technology allows significantly earlier detection of infection than immunological tests, which require that antibodies or viral proteins reach detectable levels in the body. In addition, the WNV test is conveniently run on the same test platform as the licensed Procleix HIV-1/HCV assay.