A Diagnostics & Imaging Week

Gen-Probe (San Diego), which is focused on making nucleic acid tests (NATs) that are used primarily to diagnose human diseases and screen donated human blood, reported last Thursday that the FDA had granted marketing approval to use the company’s Procleix West Nile virus (WNV) assay to screen donated human blood on the Procleix enhanced semi-automated instrument system (eSAS).

Since June 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 about 1,500 West Nile-infected units, thereby preventing transfusion of contaminated blood into as many as 4,500 people, Gen-Probe said.

“FDA approval of our West Nile virus assay represents another significant milestone in our efforts to help safeguard the U.S. blood supply with our innovative nucleic acid testing technologies,” said Henry Nordhoff, chairman, president and CEO of Gen-Probe. “The entire development program for this highly accurate assay, which began only three years ago, has been a tremendous success story for Gen-Probe.”

He added: “We appreciate the significant support we received from FDA and the National Heart, Lung and Blood Institute, which were instrumental in the development and approval of this assay.”

Based on the early approval of the WNV assay on the eSAS, as well as recent discussions with the FDA and customers, Gen-Probe said it has decided to accelerate the necessary regulatory filings for use of the WNV assay on the company’s fully automated, high-throughput Tigris system. It intends to file for this clearance in the first part of 2006.

Gen-Probe 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.

West Nile virus is a mosquito-borne virus associated with a human form of the disease ranging from mild, flu-like symptoms to severe neurological disease. The first confirmed U.S. death resulting from transmission through donated blood was reported in 2002.

In the fall of that year, 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 (Emeryville, California), 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. Gen-Probe said that, according to the Centers for Disease Control and Prevention (CDC; Atlanta), more than 2,700 human cases of WNV infection have occurred in 2005.

In an FDA Talk Paper, the agency said that to date there have been 30 documented cases of people who most likely acquired WNV from a blood transfusion, including nine who died.

“This approval is the result of a tremendous cooperative effort among FDA, other public health agencies, the test kit manufacturers and the blood industry,” said Jesse Goodman, MD, MPH, director of the agency’s Center for Biologics Evaluation and Research. “To develop an investigational test to screen blood, tissue and organ donors, and to get this test in blood banks throughout the country, and then licensed this quickly is a remarkable achievement for public health and patient safety.”

West Nile virus is typically transmitted to humans by mosquito bites. It was first detected in the U.S. in 1999, and has occurred each year for seven consecutive years, causing close to 20,000 human cases of disease and at least 762 deaths since 2002. It is estimated that between 1 million and 2 million people have been infected with WNV.

In 2002, it was discovered that WNV could be transmitted in blood and an “urgent effort” to develop a blood test began, the FDA said.

With support from FDA, the CDC and the National Institutes of Health, manufacturers developed investigational WNV tests that were rapidly put in place both to evaluate their effectiveness and as an interim measure to protect the blood supply. Blood banks across the U.S. participated in these efforts, resulting in the detection and removal of some 1,600 infected donations.