Aventis Pasteur and FibroGen to develop new vaccine stabilizers using FibroGen's recombinant biomaterials

South San Francisco, CA - January 18, 2001 - Aventis Pasteur, SA (NYSE: AVE) and the FibroGen Group today announced a collaboration agreement to develop, using FibroGen's proprietary technology, novel synthetic gelatins that will confer optimal stabilization and activity attenuation specific for certain Aventis Pasteur vaccines. The collaboration will begin immediately with joint development work focusing on selected Aventis Pasteur vaccines and potential for additional vaccines.

Term of the agreement between Aventis Pasteur and FibroGen include upfront payments, program funding, milestone payments, material supply revenues, and royalty rights on the end product sales.

"FibroGen is eager to advance its work in producing a family of safe synthetic gelatins through a strong and productive partnership with Aventis Pasteur," said Thomas B. Neff, CEO of FibroGen, Inc. "FibroGen's proprietary technology will facilitate Aventis Pasteur in fulfilling its corporate mandate to remove or reduce animal derived materials in its pharmaceutical products. By taking this step to move to FibroGen's synthetic gelatin, Aventis Pasteur has demonstrated why it remains a world leader in the vaccine marketplace."

Traditionally, the gelatins utilized in vaccines, biologics, capsules, plasma expanders, drug delivery, and other critical pharmaceutical applications have been procured from animal-derived materials and then processed batch-to-batch to meet customer needs. While the physical and biological properties of gelatin are unique, the source of the material has long challenged the industry in terms of reproducibility, consistent supply, content, and quality.

"The ability to match the stabilization needs of a specific pharmaceutical product to a gelatin engineered to meet those needs really changes the rules. We look forward to working with our new partner to explore the full potential of this emerging opportunity," said Alf Lindberg, Executive Vice-President, Research and Development at Aventis Pasteur. "As vaccinations are key to better health for people around the world, and due to the variability of the global climate, vaccines must maintain stability and effectiveness under a variety of conditions. Stabilization tools like FibroGen's engineered gelatins help Aventis Pasteur to fulfill its mission to deliver life-saving vaccines globally, and to permanently eradicate the deadliest of childhood diseases."

About FibroGen, Inc.

FibroGen, Inc., has leveraged its expertise in extracellular matrix biology by achieving the only commercially viable method known to produce human collagen and human gelatin in recombinant systems. FibroGen will exploit this technology by becoming both a bulk product supplier for the pharmaceutical and medical device industries as well as a developer and commercializer of injectable products, wound management products, and gelatin stabilizers. Additionally, FibroGen has unique therapeutic programs focusing on the development of therapies to treat fibrosis, excessive scarring, tissue regeneration, and fibroproliferative disorders including angiogenesis and squamous cell carcinoma.

FibroGen's corporate collaborations include a partnership with Taisho Pharmaceutical Company of Japan to discover and develop human monoclonal antibody therapeutics for renal fibrosis and chronic transplant rejection, as well as a joint collaboration with ZymoGenetics for the development of fully recombinant hemostats and resorbable tissue sealants utilizing FibroGen's recombinant collagen. FibroGen also has signed over 25 agreements with leading pharmaceutical and medical device manufacturers for development or feasibility testing of the Company's recombinant human collagens or gelatin as replacement components for animal-derived materials within in-market and R&D stage products.

FibroGen Europe, the majority-owned subsidiary of FibroGen, Inc., is headquartered in Helsinki, Finland. The Company's technical expertise, coupled with its substantial intellectual property position, allows FibroGen Europe to assume a leadership position in the European recombinant collagen and gelatin marketplaces. FibroGen Europe will focus on supplying its novel biomaterials to companies in the European medical device and pharmaceutical industries, as well as commercializing products of its own design. Customers interested in purchasing FibroGen's products should log-on to FibroGen's website at www.fibrogen.com and select "Reagents." Customers without web access may contact the Company's Reagent Sales Customer Service Department at 800-720-7203. FibroGen's current products are intended for laboratory research purposes only and are not to be used in humans.

About Aventis Pasteur

Aventis Pasteur, a world leader in vaccines with the broadest range of products, produces more than one billion doses of vaccines every year to immunize 400 million people around the world. Aventis Pasteur, headquartered in Lyons, France, is one of the pharmaceutical activities of Aventis SA. For more information: www.aventispasteur.com

Aventis Pasteur operated under the Pasteur Mérieux Connaught name until the creation of Aventis.

Aventis (NYSE: AVE), a world leader in pharmaceuticals and agriculture, 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. Aventis announced in November 2000 that it intends to focus on pharmaceuticals and plans to divest its activities in agriculture. With its 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 Rhône-Poulenc SA of France. For more information: 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.