December 1, 2004

XDx, Inc. Completes $20 Million Private Equity Financing

SOUTH SAN FRANCISCO, Calif., Dec. 1 /PRNewswire/ -- XDx, Inc., a molecular diagnostics company, announced today that it has completed a $20 million Series D private equity financing. Sprout Group led the investment, with additional participation from new investors JP Morgan's Bay Area Equity Fund, Integral Capital Partners and Burrill & Company, as well as existing investors Kleiner Perkins Caufield & Byers and TPG Ventures.

With the proceeds of the financing, XDx will launch AlloMap molecular expression testing, the first blood sample-based test developed to manage the complex immunologic questions posed by cardiac transplant patients. The XDx Reference Laboratory received CLIA (Clinical Laboratory Improvement Amendment) certification on November 23, 2004, and will begin the launch of AlloMap molecular expression testing this month to leading transplant centers across the country that participated in the validation trial. AlloMap molecular expression testing will become widely available to all U.S. transplant centers in 2005.

In connection with the financing, Vijay Lathi, a partner at Sprout Group investing in healthcare technology, has joined XDx's Board. Mr. Lathi commented, "XDx fits Sprout Group's investment strategy in molecular diagnostics because its tests can redefine disease with quantitative and molecular information that improve diagnosis allowing for more precise treatment. The company will be one of the first to commercialize a gene expression-based diagnostic, with the potential to significantly improve clinical care. XDx's first product, AlloMap molecular expression testing, which monitors rejection in cardiac transplants, could reduce the need for biopsy. Sprout also invested in XDx because of the high quality of the senior team, which has a strong background launching new products and building businesses in the diagnostics industry."

Brook Byers, general partner of Kleiner Perkins Caufield and Byers, said, "XDx is already one of the leaders in the important new field of personalized medicine enabled through molecular diagnostics. We believe that XDx's products can ultimately improve medical decision-making, reduce pain and suffering of patients, and decrease overall health care costs."

Approximately 4,500 new cardiac transplants are performed annually, and more than 30,000 patients living with transplanted hearts visit their physicians an aggregate of 100,000 times per year to be evaluated for evidence that they are rejecting their transplant (or allograft). This is traditionally done through multiple biopsies, particularly in the first year, which provide negative results 75 percent of the time. XDx's AlloMap molecular expression testing offers a technologically advanced alternative to the conventional method and is designed to reduce the need for endomyocardial biopsy -- an invasive, expensive and subjective procedure.

"We have put together a great team at XDx, as well as a wonderful group of investors with a depth of experience and understanding of the diagnostics and healthcare industry," said Pierre Cassigneul, president and chief executive officer of XDx. "We believe that our technology platform, non-invasive assays based on peripheral blood, can play a critical role in medicine and may find application in numerous diseases, including autoimmune and chronic inflammatory diseases, as well as organ and bone marrow transplantation."

Tammy Reilly, vice president, Commercial Operations of XDx, said, "In preparation for commercial launch, we are currently hiring and expect to have most of our national sales team in place by March 2005. Our strategy is to cover all 252 transplant centers in the United States. To this end, we are focused on hiring individuals with strong backgrounds in transplantation, immunology or specialty diagnostic sales to achieve rapid market penetration."

About AlloMap molecular expression testing

XDx's AlloMap molecular expression testing is a non-invasive assay based on peripheral blood that detects cardiac allograft rejection. Specifically, the test measures immune cells in the peripheral blood that cause and respond to cardiac allograft rejection. When used in conjunction with clinical judgment and assessment of graft function, molecular expression testing may reduce endomyocardial biopsies and immunosuppression therapy.

About XDx, Inc.

Founded in 2000, XDx is a molecular diagnostics company located in South San Francisco, CA. XDx scientists have applied microarray, RT-PCR (real time polymerase chain reaction) and bioinformatics technologies to develop a clinically useful way to monitor the immune system. This work provides the basis for XDx's broad pipeline of AlloMap(TM) non-invasive monitoring assays. In 2004, XDx completed the validation phase of the CARGO (Cardiac Allograft Rejection and Gene Expression Observational) study in anticipation of a December 2004 launch of AlloMap molecular expression testing, the company's molecular expression test targeting the post-cardiac transplantation patient management market. More information on XDx, Inc. can be found by visiting

XDx, Inc.

CONTACT: Pierre Cassigneul or Tammy Reilly, both of XDx,+1-650-624-0120

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