PRESS RELEASE from Aventis Behring

Contacts: Reilly Kim (610-878-4822) or Todd Martine (212-642-7731)

EMBARGOED UNTIL December 4, 2001

AVENTIS BEHRING ANNOUNCES SUCCESSFUL RESULTS FOR FIRST RECOMBINANT ALBUMIN PHASE I CLINICAL TRIAL
Clinical Results Suggest Increased Standards of Purity for Pharmaceutical and Biological Products

King of Prussia, PA, December 4, 2001 - Aventis Behring L.L.C. announced today the successful results of its large, pivotal Phase I clinical trial for Recombumin20%. The trial was designed to assess the tolerability of Recombumin20% as a stabilizing component in pharmaceutical and biological products, such as vaccines, recombinant therapies and coatings for medical devices.

Recombumin20% is a recombinant, or completely biosynthetic, human albumin product. The manufacturing process begins with fermentation in yeast, yielding a product that is free of human or animal-derived material with a level of purity that is unparalleled in biological products. Manufacturers of biological products can use Recombumin20% as a stabilizing agent for new therapies in development or by replacing less optimal stabilizers in their existing products.

Delta Biotechnology Ltd., a wholly owned subsidiary of Aventis Behring, is already producing Recombumin20% in small amounts. "We believe Recombumin20% can raise the standard of purity and safety in important therapies already developed to prevent and treat diseases around the world. Because it is a recombinant product derived from fermentation in yeast, there is not even a theoretical risk that it will transmit any known, unknown or newly emerging infectious agents," stated Werner Merkle, Vice President and General Manager of Delta Biotechnology Ltd.

"Recombumin20% symbolizes the future of Aventis Behring as we continue to combine state-of-the-art technology with our rich heritage in plasma therapy."

Between November, 1999 and June, 2000, five-hundred subjects were included in this double-blind, randomized, parallel-group, dose-escalating study comparing Recombumin20% to human serum albumin 20%. The trial was conducted in Sweden under a United States Food and Drug Administration Investigational New Drug Application (IND). The volunteers received intramuscular administrations, once a week for five consecutive weeks, of either Recombumin20% or human serum albumin (HSA) 20% at dose levels of 5 mg (100 subjects), 15 mg (100 subjects) or 65 mg (300 subjects).

The results of the study demonstrated the safety and good tolerability of Recombumin20% up to a dose of 65 mg. Since the expected highest single dose is 15 mg, the good tolerability of the 65 mg dose provides an excellent safety margin. The overall incidence of adverse events, (e.g. those referring to allergic reactions), was low and comparable between the Recombumin20% and the human serum albumin 20% treatment groups.

No dose-related increase in adverse events could be detected. Recombumin20% is one of several state-of-the-art products in Aventis BehringÕs pipeline. Aventis Behring is committed to developing the next generation of therapeutic proteins to serve unmet medical needs, and expanding its already rich pipeline. Other products under development include alpha1 proteinase inhibitors, liquid immunoglobulin, monoclonal antibodies and fibrin sealants. Delta Biotechnology Ltd. is based in Nottingham, United Kingdom, and is a wholly owned subsidiary of Aventis Behring L.L.C. Delta Biotechnology is dedicated to the development of proprietary technologies for high yield recombinant expression and purification systems for therapeutic proteins.

Delta Biotechnology has also established a technology and patent leadership position for albumin fusion proteins, a sophisticated molecular approach which may improve the clinical efficacy of many therapeutic proteins. For certain areas of application this technology was licensed to Principia Pharmaceuticals, a fast-growing biotechnology company recently acquired by Human Genome Sciences.

Aventis Behring L.L.C. 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, please visit www.aventisbehring.com.

Aventis Behring is the plasma protein business of Aventis Pharma AG. Aventis Pharma AG is the pharmaceutical subsidiary of Aventis S.A. Aventis (NYSE: AVE) is a world leader in life sciences. Focused on two core business areas - pharmaceuticals and agriculture - Aventis is dedicated to improving life through the discovery and development of innovative products in the fields of prescription drugs, vaccines, therapeutic proteins, crop production and protection, animal health and nutrition.

With global corporate headquarters in Strasbourg, France, Aventis employs around 95,000 people in more than 120 countries and recorded pro forma sales in 1999 of 20.5 billion euros. Aventis was launched in December 1999 through the merger of Hoechst AG of Germany and Rhone-Poulenc SA of France.

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