The U.S. Food and Drug Administration (FDA) has granted marketing approval to use the Gen-Probe's PROCLEIX® West Nile virus (WNV) assay to screen donated human blood on the PROCLEIX enhanced semi-automated instrument system (eSAS).

Since June of 2003, U.S. blood centers have used the PROCLEIX WNV assay to screen more than 29 million units of donated blood under an investigational new drug (IND) application. This experimental testing has intercepted approximately 1,500 West Nile-infected units, thereby preventing transfusion of contaminated blood into as many as 4,500 people.

Based on the early approval of the WNV assay on the eSAS, as well as recent discussions with the FDA and customers, Gen-Probe has decided to accelerate the necessary regulatory filings for use of the WNV assay on the Company’s fully automated, high-throughput TIGRIS system. Gen-Probe intends to file for this clearance in the first part of 2006. The Company then expects to pursue clearance of the TIGRIS system to run the PROCLEIX ULTRIO assay, which simultaneously detects HIV-1, hepatitis C virus and hepatitis B virus.

The first confirmed U.S. death resulting from WNV transmission through donated blood was reported in 2002. In the fall of 2002, the FDA challenged industry to develop a test for the direct detection of WNV in donated blood by the summer of 2003. Within nine months, Gen-Probe and its partner Chiron had developed the PROCLEIX WNV assay and began distributing it under an IND. WNV has continued to be a significant public health threat since that time. According to the U.S. Centers for Disease Control and Prevention, more than 2,700 human cases of WNV infection have occurred in 2005.