Contacts:

Patrick Plewman diaDexus, Inc. (650) 246-6400

Carolyn Bumgardner Wang WeissComm Partners (415) 362-5018 x123 carolyn@weisscommpartners.com

Scientific Sessions Abstract Oral Presentation #1183

STUDY HIGHLIGHTS THE ROLE OF Lp-PLA2 AND INFLAMMATION IN THE FORMATION OF VULNERABLE PLAQUE - A MAJOR CAUSE OF HEART ATTACK AND STROKE

New Orleans, LA - November 9, 2004 - diaDexus today announced findings from a new study that indicate a biological role for Lp-PLA2 (lipoprotein-associated phospholipase A2) in the formation of vulnerable plaque.w The data were presented at the American Heart Association (AHA) Scientific Sessions held in New Orleans this week.

"Our findings reveal that Lp-PLA2 is not only a highly specific marker of vascular inflammation, but also may play an important role in plaque instability and the formation of vulnerable plaque," said Renu Virmani, M.D., Department of Cardiovascular Pathology, Armed Forces Institute of Pathology, Washington, DC, study investigator and a world-renowned expert in this area.

In the study, specific monoclonal antibodies were used to identify Lp-PLA2 in serial frozen or paraffin-embedded sections of atherosclerotic plaques from sudden coronary death victims. The data demonstrate that Lp-PLA2 localizes with inflammatory cells and is strongly expressed in the core of atheromas often associated with acute coronary events. In the most rupture prone plaque, Lp-PLA2 was also highly prominent within the thin fibrous cap, suggesting that Lp-PLA2 and its enzymatic byproducts may play a role in promoting plaque instability.

Despite major advances in the understanding and management of cardiovascular disease, a large number of patients die suddenly, often without prior symptoms. Evaluating the cellular components of plaque and markers associated with plaque formation could lead to improved detection and management of high-risk patients.

"Several studies have demonstrated that elevated Lp-PLA2 levels in plasma correlate with an increased risk of a coronary event," said Bob Wolfert, Ph.D., Vice President of Diagnostics at diaDexus. "This study highlights the active role of Lp-PLA2 in atherosclerotic plaque and its potential role in plaque rupture."

Dr. Virmani's study was supported by a grant from diaDexus.

About Lp-PLA2
Lp-PLA2 (lipoprotein-associated phospholipase A2) is an enzyme that is implicated in the vascular inflammatory pathway that leads to plaque formation and atherosclerosis. Previous hypotheses on the cause of coronary heart disease focused around lipid accumulation within the arterial walls. Increasing evidence now suggests that atherosclerosis is largely an inflammatory disease. The MONICA (MONItoring of trends and determinants in CArdiovascular disease) study, published in the October 2004 issue of Circulation, was the third study published in a peer-reviewed journal to show a statistically significant relationship between elevated Lp-PLA2 and the risk of a coronary event. Among individuals in the MONICA population, each standard deviation increase in Lp-PLA2 levels resulted in a 37% increase in the risk of a coronary event.

About diaDexus
diaDexus, a privately held biotechnology company, based in South San Francisco, California, is focused on the discovery, development and commercialization of novel, patent-protected diagnostic and therapeutic products with high clinical value. The PLAC test, developed by diaDexus, is a blood test cleared by the U.S. Food and Drug Administration to aid in the prediction of an individual's risk for a coronary event, in conjunction with clinical evaluation and patient risk assessment. The PLAC test is currently available through laboratories nationwide. For more information about the PLAC test visit www.plactest.com. More information about the company may be found at www.diaDexus.com.