Contacts:

Sharon Tetlow diaDexus, Inc. (650) 246-6400

Krysta Walkowiak Wang Dorland Global Health Communications (415) 262-5211 Cell: (415) 517-2236 kwalkowiak@dorland.com

LP-PLA2 TARGETED FOR THERAPEUTIC INTERVENTION

diaDexus offers FDA-cleared test to measure Lp-PLA2

South San Francisco, CA - December 17, 2003 - At a presentation to investors earlier this month, GlaxoSmithKline (GSK) announced positive Phase II data for a novel compound that dramatically lowers activity of lipoprotein-associated phospholipase A2 (Lp-PLA2). This Lp-PLA2 inhibitor may represent a new generation of drugs that reduce cardiovascular disease and death. GSK expects the Lp-PLA2 inhibitor to move into Phase III trials in 2004.

"diaDexus has developed and markets the PLAC™ test, a test that measures the levels of Lp-PLA2 in blood," said Patrick Plewman, president and CEO of diaDexus. "Several studies have identified Lp-PLA2 as a novel, independent risk factor for coronary events."

Last July, the U.S. Food and Drug Administration (FDA) granted diaDexus marketing clearance for the PLAC test. The test was approved as an aid in predicting an individual's risk for coronary heart disease, in conjunction with clinical evaluation and patient risk assessment. The Lp-PLA2 enzyme was discovered by SmithKline Beecham scientists through the use of Human Genome Sciences, Inc.'s (HGSI) technology, enabling diaDexus to develop the PLAC test.

diaDexus was founded in 1997 by SmithKline Beecham, now GSK, and Incyte Corporation to develop patent protected, clinically important, high value diagnostic tests. diaDexus has certain exclusive rights to develop commercial diagnostic tests, like the PLAC test, based on SmithKline Beecham's drug discovery efforts.

Quest Diagnostics and Mayo Medical Laboratories offer testing for Lp-PLA2.

For more information on the PLAC™ test please visit www.plactest.com.

About diaDexus
diaDexus, Inc., a privately held biotechnology company, based in South San Francisco, Calif., is focused on the discovery, development and commercialization of novel, patent-protected diagnostic and therapeutic products with high clinical value. diaDexus utilizes genomics and bioinformatics to identify numerous disease-associated molecular targets. More information about the company may be found at www.diaDexus.com.