Regeneron Pharmaceuticals Announces VelociGene(R) Agreement with Sanofi-Aventis (France); Regeneron to Receive Minimum of $21.5

Regeneron Pharmaceuticals Announces VelociGene(R) Agreement with Sanofi-Aventis (France); Regeneron to Receive Minimum of $21.5 Million

TARRYTOWN, N.Y. -- Regeneron Pharmaceuticals, Inc. (Nasdaq: REGN - News) announced today that it has entered into an agreement with sanofi-aventis (Euronext: SAN and NYSE: SNY) to use Regeneron's proprietary VelociGene technology platform to supply sanofi-aventis with genetically modified mammalian models of gene function and disease. Sanofi-aventis will pay Regeneron a minimum of $4.3 million annually for five years for knock-out and transgenic models of gene function for target genes identified by sanofi-aventis. Sanofi-aventis will use these models for its internal research programs, outside the scope of its antibody collaboration with Regeneron.

In November 2007, Regeneron and sanofi-aventis entered into a collaboration agreement for the discovery, development, and commercialization of human monoclonal antibodies based on Regeneron's proprietary VelociSuite of technologies, including VelociGene®, VelociMouseTM, VelocImmune®, and VelociMabTM. Over the first five years of the antibody agreement, sanofi-aventis is funding discovery research at Regeneron, including target identification, target validation, and antibody development. The VelociGene payments are in addition to the funding to be provided under the antibody agreement.

"We have extensive experience using the VelociGene platform as part of our internal research activities, and it has proven to be extremely useful for identifying new gene targets for drug research and development," noted David Valenzuela, Ph.D., Vice President of Functional Genomics and Chief of VelociGene Operations at Regeneron. "It is gratifying that scientists at sanofi-aventis appreciate the unique potential of VelociGene to produce rapidly and precisely, customized knock-out and transgenic expression models."

About VelociGene

The Regeneron VelociGene platform allows custom and precise manipulation of very large sequences of DNA to produce highly customized alterations, ranging from a single nucleotide to many millions of nucleotides, of a specific target gene and accelerates the production of knock-out and transgenic expression models without using either positive/negative selection or isogenic DNA. For example, in producing knock-out models, a color or fluorescent marker is substituted in place of the actual gene sequence, allowing for high-resolution visualization of precisely where the gene is active in the body, during normal body functioning, as well as in disease processes. Among other uses, VelociGene allows scientists to rapidly identify the physical and biological effects of deleting or over-expressing the target gene, as well as to characterize and test potential therapeutic molecules.

About Regeneron Pharmaceuticals

Regeneron is a fully integrated biopharmaceutical company that discovers, develops, and commercializes medicines for the treatment of serious medical conditions. In addition to ARCALYST® (rilonacept) Injection for Subcutaneous Use, its first commercialized product, Regeneron has therapeutic candidates in clinical trials for the potential treatment of cancer, eye diseases, and inflammatory diseases, and has preclinical programs in other diseases and disorders. Additional information about Regeneron and recent news releases are available on the Regeneron web site at

Forward Looking Statement

This news release discusses historical information and includes forward-looking statements about Regeneron and its products, development programs, finances, and business, all of which involve a number of risks and uncertainties, such as risks associated with preclinical and clinical development of Regeneron's drug candidates, determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron's ability to continue to develop or commercialize its product and drug candidates, competing drugs that are superior to Regeneron's product and drug candidates, uncertainty of market acceptance of Regeneron's product and drug candidates, unanticipated expenses, the availability and cost of capital, the costs of developing, producing, and selling products, the potential for any collaboration agreement, including Regeneron's agreements with the sanofi-aventis Group and Bayer HealthCare, to be canceled or to terminate without any product success, risks associated with third party intellectual property, and other material risks. A more complete description of these and other material risks can be found in Regeneron's filings with the United States Securities and Exchange Commission (SEC), including its Form 10-K for the year ended December 31, 2007 and Form 10-Q for the quarter ending June 30, 2008. Regeneron does not undertake any obligation to update publicly any forward-looking statement, whether as a result of new information, future events, or otherwise unless required by law.