Regeneron Increases Size of Public Offering of Common Stock

NEW YORK,Oct. 8/PRNewswire-FirstCall/ -- Regeneron Pharmaceuticals, Inc. (Nasdaq:REGN) today announced that it has increased the size of its previously announced underwritten public offering of Common Stock from 4,500,000 shares to 5,500,000 shares and agreed to an indicative price of$28.00per share for the offering. Citi is serving as sole book-running manager for the offering. The offering is expected to close onOctober 13, 2010, subject to customary closing conditions.  In addition, Regeneron has granted Citi a 30-day option to purchase up to an additional 825,000 shares of Common Stock to cover over-allotments, if any. The shares are being offered by Regeneron under the Company's shelf registration statement.

This press release shall not constitute an offer to sell, or the solicitation of an offer to buy, any of the securities, nor shall there be any sale of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such jurisdiction.  Copies of the prospectus supplement and accompanying prospectus related to this offering may be obtained by sending a request to the offices of Citi at Brooklyn Army Terminal, 140 58th Street, 8th Floor,Brooklyn, NY11220, telephone number (800) 831-9146.  Alternatively, these documents are available by visiting EDGAR on the SEC website atwww.sec.gov.

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 Phase 3 clinical trials for the potential treatment of gout, diseases of the eye (wet age-related macular degeneration and central retinal vein occlusion), and certain cancers.  Additional therapeutic candidates developed from proprietary Regeneron technologies for creating fully human monoclonal antibodies are in earlier stage development programs in rheumatoid arthritis and other inflammatory conditions, pain, cholesterol reduction, allergic and immune conditions and cancer.  Additional information about Regeneron and recent news releases are available on Regeneron's web site atwww.regeneron.com.

This news release includes forward-looking statements about Regeneron and its products, development programs, finances, and business, all of which involve a number of risks and uncertainties. These include, among others, risks and timing 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 license or collaboration agreement, including Regeneron's agreements with Astellas, the sanofi-aventis Group and Bayer HealthCare, to be canceled or terminated without any product success, and risks associated with third party intellectual property. 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 endedDecember 31, 2009and Form 10-Q for the quarter endedJune 30, 2010. 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.

Michael Aberman, M.D.

Peter Dworkin

Investor Relations

Corporate Communications

914.345.7799

914.345.7640

[email protected]

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