Contacts:

Barbara Sullivan Sullivan& Associates (714) 374-6174 bsullivan@sullivanpr.com

Christina Andrian diaDexus, Inc. (650) 246-6476 candrian@diadexus.com

EXTENDED RELEASE NIACIN REDUCES CARDIOVASCULAR INFLAMMMATORY MARKER LP-PLA2

diaDexus' PLAC® Test Measures Key Enzyme to Help Guide Treatment Conditions

South San Francisco, CA - October 9, 2006 - Niacin, in conjunction with statin therapy, reduces lipoprotein-associated phospholipase A2 (Lp-PLA2), an important new marker of inflammation associated with heart disease and stroke due to plaque rupture, according to a study published in the September 15, 2006, issue of The American Journal of Cardiology. The study, conducted at Tufts-New England Medical Center, evaluated 54 patients who were assigned either 1,000 mg daily extended release niacin or placebo, in addition to their existing drug regimen, primarily statins, ACE inhibitors, and aspirin.

The study shows that when extended release niacin was administered to stable heart disease patients for three months, Lp-PAL2 levels were reduced by 20 percent ( p‹0.05 ), while low-density lipoprotein (LDL) remained unchanged. Lp-PAL2 levels were measured by the PLAC test from diaDexus. The PLAC test is a simple blood test that measures the concentration of the enzyme Lp-PAL2, identifying people at high risk for heart disease and stroke associated with atherosclerosis, who may not be identified by traditional risk factors.

According to clinical investigator Jeffrey T. Kuvin, M.D., the results add to the growing knowledge about Lp-PAL2. "It is well-established that inflammation, as measured by biomarkers such as Lp-PAL2, plays a critical role in atherogenesis," Kuvin said. "This study adds another critical component, demonstrating further therapeutic benefits of adding niacin to existing medical regimens of heart disease patients with already well-controlled LDL-reduced inflammation and increased lipoprotein particle size."

The results also showed that niacin changed the cholesterol particle-size of patients, with large particle high-density lipoprotein (HDL) increasing 32 percent (p‹0.001). Large HDL appears to be more protective against heart disease than small HDL. In this study, niacin also reduced C-reactive protein levels by 15 percent (p‹0.05), and increased total HDL 7.5 percent (p‹0.005). Total cholesterol remained unchanged.

"Determining which high-risk patients should be targeted with more aggressive therapy is not clearly defined in guidelines, and physicians often are unsure which patients may benefit from a more intensive treatment approach," said Richard B. Lanman, M.D., chief medical officer of diaDexus. "The PLAC test uncovers critical information about risk for cardiovascular events to help guides those treatment decisions."

Heart disease is the single leading cause of death in the United States, killing almost 500,000 Americans each year. It also is the most costly-the estimated direct and indirect cost of heart disease in 2006 is $142.5 billion.

Lp-PAL2 is an enzyme that associates in the blood primarily with LDL, the "bad" cholesterol. Lp-PAL2 is carried to the walls of coronary arteries by LDL, where the enzyme can activate an inflammatory response, promoting atherosclerosis. As a result, Lp-PAL2 serves as a specific indicator of vascular inflammation. Individuals identified as being at high risk for coronary heart disease or stroke based on elevated Lp-PAL2 levels are candidates for proactive preventive measures, such as lifestyle modification and therapeutic intervention.

About diaDexus
diaDexus, Inc., a privately held biotechnology company based in South San Francisco, is focused on the discovery, development, and commercialization of clinically valuable, patent-protected diagnostic products.

For more information, visit www.plactest.com or www.diaDexus.com