Aventis Behring Research Confirms Inactivation of West Nile Virus From Its Plasma-Derived Therapies Through Its Current Plasma Purification Methods.

Health/Medical Writers

KING OF PRUSSIA, Pa.--(BUSINESS WIRE)--Dec. 6, 2002

Aventis Behring Initiated Studies

to Address Patient Community Concerns

Aventis Behring L.L.C. today announced results from studies that confirmed that its current virus inactivation methods effectively inactivate or eliminate the potential presence of West Nile Virus (WNV) from its plasma-derived products.

Concurrently, the studies also confirmed that the risk of WNV transmission through Aventis Behring plasma-derived products is virtually non-existent. Details of Aventis Behring's continuing efforts to safeguard its therapies

from WNV were also summarized in a recent letter to the National Hemophilia Foundation.

Aventis Behring initiated these studies to address concerns expressed by patients and customers given the reports of potential WNV transmission through blood transfusion and organ transplant procedures. The results announced today are the first in a series of "spiking" studies in which WNV and Bovine Viral Diarrhea Virus (BVDV), (a virus from the same family that is often used in virus validation studies as a model virus for WNV, Hepatitis C virus, and other flaviviruses), are intentionally introduced into samples of plasma-derived therapies.

Collectively, the study results demonstrate that the rigorous virus inactivation steps currently used by Aventis Behring in the production of plasma-derived products successfully inactivate WNV and BVDV (and related viruses). Furthermore, the study confirms that BVDV, used in Aventis Behring's virus validation studies, is the appropriate model virus for virus inactivation validation studies since it is more robust than WNV.

"We understand the concerns of the community over the perceived threat of WNV transmission, and have been diligent in researching and testing current procedures against WNV in our continued efforts to protect our patients and provide them with life-saving plasma-derived products. Based on our findings, we believe that current safety methods employed to destroy and eliminate other viruses like Hepatitis C also effectively inactivate and remove WNV in plasma-derived protein therapeutics," said Dr. Ruedi Wager, Chief Executive Officer of Aventis Behring.

FDA Conclusions

On their Web site, the U.S. Food and Drug Administration (FDA) offered the following conclusion regarding the potential risk for transmission of WNV with plasma-derived products, "The risk of transmission by plasma derivatives is considered extremely low. WNV is a lipid-enveloped virus and is likely to be effectively inactivated by processes in place for these products, which have been shown to inactivate closely related viruses." Aventis Behring's study confirms FDA's supposition.

About West Nile Virus (WNV)

WNV is a lipid-enveloped member of the family Flaviviridae whose members also include the Hepatitis C virus and the Bovine Viral Diarrhea Virus (BVDV), and is of the same genus as dengue virus and yellow fever virus. WNV is known to be an insect-borne disease transmissible to humans, birds and other vertebrates through the bite of a carrier mosquito. WNV, commonly found in Africa, Eastern Europe, West Asia and the Middle East, is thought to have arrived in the Western Hemisphere in 1999. Approximately 80 percent of people infected with WNV show no symptoms, but 20 percent may develop flu-like symptoms and, in rare cases, may develop encephalitis or meningitis. According to a November 29, 2002 report issued by the Centers for Disease Control and Prevention, approximately 3,737 confirmed human cases have been reported in the U.S.

About Aventis Behring

Aventis Behring L.L.C., part of the Aventis family of companies, is a global leader in the plasma protein industry, providing a wide range of innovative, high quality therapies and unique support services to patients worldwide. Aventis Behring is dedicated to the research and development of proteins from human blood plasma and emerging technologies. For more information about the company, visit its website at www.aventisbehring.com.

Aventis (NYSE: AVE) is dedicated to improving life by treating and preventing human disease through the discovery and development of innovative prescription drugs for important therapeutic areas as well as human vaccines. In 2001, Aventis generated sales of euro 17.7 billion, invested euro 3 billion in research and development and employed approximately 75,000 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.