Aventis has returned development rights for DiaPep277? for type 1diabetes to DeveloGen and ended its collaborative agreement on that compound with DeveloGen. At this point, Aventis has determined the development project no longer meets its corporate business priority criteria for progression, and has decided to focus on other compounds in its diabetes pipeline. Details were not disclosed.

About Aventis

Aventis is dedicated to treating and preventing disease by discovering and developing innovative prescription drugs and human vaccines. In 2003, Aventis generated sales of ? 16.79 billion, invested ? 2.86 billion in research and development and employed approximately 69,000 people in its core business. Aventis corporate headquarters are in Strasbourg, France. For more information, please visit: www.aventis.com

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Actual results could differ materially depending on factors such as the timing and effects of regulatory actions, the results of clinical trials, the company?s relative success developing and gaining market acceptance for new products, the outcome of significant 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 and in the current Annual Report -"Document de R?f?rence"- on file with the "Commission des Op?rations de Bourse" in France.

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Aventis Press Release