Contacts:

Sharon Tetlow Vice President, Chief Financial Officer diaDexus 650-246-6400 stetlow@diadexus.com

DIADEXUS COLLABORATES WITH MAYO MEDICAL LABORATORIES AND MAYO CLINIC TO EXPAND CLINICAL APPLICATIONS FOR CARDIOVASCULAR RISK ASSESSMENT TEST

South San Francisco, CA and Rochester, MN - April 17, 2002 - /PRNewswire/ - diaDexus, Inc., a privately-held biotechnology company, Mayo Clinic, and Mayo Medical Laboratories, the national reference laboratory for Mayo Clinic, today announced that they have entered into a collaborative agreement to explore the clinical applications for a test that detects a newly identified independent risk factor for cardiovascular disease.

The test, called the PLAC(TM) Test, was developed by diaDexus as a potential new way to assess an individual's risk for cardiovascular diseases, particularly in patients who do not exhibit traditional risk factors such as elevated cholesterol, high blood pressure or diabetes. This novel proprietary technology detects the enzyme lipoprotein-associated phospholipase A2 (Lp-PLA2).

A study published in The New England Journal of Medicine in October 2000 demonstrated that Lp-PLA2 is independently predictive of those at risk for cardiovascular disease compared to both traditional risk factors, such as LDL-cholesterol, and markers of systemic inflammation, such as C-Reactive Protein (CRP).

Under terms of this agreement, Mayo and Mayo Medical Laboratories will conduct various clinical research studies to further explore a number of potential applications of the PLAC Test in a variety of cardiovascular care settings. The agreement also provides Mayo Medical Laboratories non-exclusive rights to offer the PLAC Test to its laboratory clients.

"By collaborating with diaDexus, we will be able to expand our knowledge of Lp-PLA2 and study the PLAC Test's efficacy in a broader range of clinical settings," said Joseph McConnell, PhD., co-director of the Biochemical Genetics Laboratory at Mayo Clinic.

"Our work with Mayo will provide important new diagnostic information that could eventually result in helping to reduce the number of heart attacks and strokes each year and lead to other clinical and pharmacoeconomic benefits," said Patrick Plewman, President and Chief Executive Officer of diaDexus. "Approximately 50 percent of individuals who suffer a heart attack have normal cholesterol levels, clearly indicating the need for novel tests such as the PLAC Test to measure other risk factors."

GlaxoSmithKline is developing inhibitors to Lp-PLA2 as potential anti-atherosclerosis therapies. When diaDexus was formed, GlaxoSmithKline licensed commercial diagnostic rights to Lp-PLA2 to diaDexus.

According to the American Heart Association, approximately 645,000 people die each year from heart attack or stroke and approximately 60 million Americans have some form of cardiovascular disease that could eventually lead to a heart attack or stroke, making early detection of risk factors crucial. Known risk factors such as high cholesterol, smoking, obesity and high blood pressure are not always present among patients at risk, indicating the need for the identification of new risk factors.

About diaDexus
diaDexus, 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. diaDexus has utilized genomics and bioinformatics to identify thousands of disease-associated molecular targets. Currently, diaDexus has three diagnostic product candidates in late-stage pre-clinical development. For more information, please visit www.diaDexus.com.

About Mayo Medical Laboratories
Mayo Medical Laboratories provides esoteric testing services and pathology consultation to hospitals, laboratories and clinics throughout the United States and abroad. It works with laboratory experts in disease and technology, and Mayo Clinic scientists and clinicians to investigate and offer diagnostic tests that improve patient care. The ability to explore new laboratory technology in a large integrated clinical practice environment makes Mayo Medical Laboratories unique among reference laboratories.

The statements in this press release that are not historical facts or information may be forward-looking statements. These forward-looking statements involve risks and uncertainties that could cause the outcome to be materially different from the outcome described in these forward-looking statements.