Aventis Behring Develops Improved Diagnostic Test to Detect Human Prions.

Business Editors/Health/Medical Writers

KING OF PRUSSIA, Pa.--(BUSINESS WIRE)--July 14, 2003

Advance in Prion Testing Can Enable Rapid Detection at High

Sensitivity Compared to Available Methods, Data Published

in Journal of General Virology 

Aventis Behring L.L.C. announced today that it developed an improved method designed to increase the sensitivity of a test to detect human prions, the infectious proteins thought to be responsible for Creutzfeldt-Jakob Disease (CJD) and variant Creutzfeldt-Jakob Disease (vCJD), the human form of mad-cow disease. Data generated with the test, called the "sandwich" Conformation-Dependent Immunoassay (CDI), suggest that it can detect human prions spiked in plasma with up to 100 times greater sensitivity than the original "direct" CDI that the company had developed in 1998 in collaboration with Nobel Laureate Dr. Stanley Prusiner.

"Aventis Behring is committed to striving to protect the safety of patients who depend on our life-saving therapies, and our technological advances continually redefine the standards for our industry," said Dr. Henry Baron, Senior Director of Medical and Scientific Affairs. "Although the risk that prions are present in plasma is only theoretical, the sandwich CDI may provide the scientific and medical communities with a powerful tool that can more rapidly and more accurately study prion diseases such as vCJD."

The sandwich CDI is based on the direct CDI, an ELISA (enzyme linked immunoabsorbent assay)-formatted, time-resolved fluorescence (TRF) immunoassay that can differentiate between the pathogenic and non-pathogenic forms of prion proteins as well as detect very low levels of prions in CJD or vCJD infected samples.

Prion proteins in the sample are "sandwiched" between two antibodies. The first (the capture antibody) secures the prion so that the second (the detection antibody) can effectively mark the prion for purposes of identification. Together, this sandwich effect increases this assay's sensitivity for the detection of human prions. According to the July 2003 edition of the Journal of General Virology, the sandwich CDI is 30 to 100 times more sensitive than the direct CDI, http://vir.sgmjournals.org/cgi/reprint/84/7/1921.pdf

Aventis Behring will use the sandwich CDI as a research tool to learn more about prions and to conduct additional studies that track their potential removal by the plasma protein manufacturing processes. Thus far, Aventis Behring has invested more than 20 million dollars toward this research.

Understanding Prions

Prions are infectious proteins that alter their normal protein counterparts into a pathogenic conformation that the body is unable to break down, causing them to accumulate in--and ultimately destroy--brain and nerve tissue. However, since no evidence exists to support the presence of prions in or the transmission of vCJD by blood or plasma, the exact biophysical nature of prions in bodily fluids is unknown. Prions are thought to cause neurodegenerative disorders such as bovine spongiform encephalopathy (BSE), also known as mad cow disease. Human prion diseases have also been recognized. Currently, the best understood is Creutzfeldt-Jakob Disease (CJD). CJD has been recognized and tracked since the 1920s and the incidence has not changed significantly in that time. Variant Creutzfeldt-Jakob Disease is the human form of mad-cow disease, which experts attribute to the consumption of meat products derived from BSE-infected cows.

About Aventis Behring

Aventis Behring, part of the Aventis family of companies, is a global leader in the plasma protein industry, providing a wide range of innovative and high-quality medicines to patients worldwide. Aventis Behring is dedicated to research and development in the area of human blood plasma as well as in emerging technologies. For more information about Aventis Behring, please visit our web site at www.AventisBehring.com.

Aventis (NYSE: AVE) is dedicated to treating and preventing disease by discovering and developing innovative prescription drugs and human vaccines. In 2002, Aventis generated sales of EUR 17.6 billion, invested EUR 3.1 billion in research and development and employed approximately 71,000 people in its core business. Aventis corporate headquarters are in Strasbourg, France. For more information, please visit: www.aventis.com.

Statements in this news release other than historical information are forward-looking statements subject to risks and uncertainties. Actual results could differ materially depending on factors such as the availability of resources, the timing and effects of regulatory actions, the strength of competition, the outcome of litigation and the effectiveness of patent protection. Additional information regarding risks and uncertainties is set forth in the current Annual Report on Form 20-F of Aventis on file with the Securities and Exchange Commission.