Regeneron Pharmaceuticals, Inc. Announces The Sale of 4,500,000 Shares of Common Stock

NEW YORK,Oct. 6/PRNewswire-FirstCall/ -- Regeneron Pharmaceuticals, Inc. (Nasdaq:REGN) (the "Company"), today announced that it intends, subject to market conditions, to offer 4,500,000 shares of its common stock pursuant to an underwriting agreement with Citi acting as the sole bookrunner.

The Company expects to use the net proceeds from the sale of the shares for general corporate purposes.  Closing of the offering is expected to occur on or aboutOctober 11, 2010, subject to customary closing conditions.  In addition, the Company intends to grant the underwriter a 30-day option to purchase up to an additional 675,000 shares of common stock to cover over-allotments, if any.

The offering is being made pursuant to an effective shelf registration statement.  Before you invest, you should read the base prospectus in such shelf registration statement, the prospectus supplement, when available, and other documents the Company has filed with the Securities and Exchange Commission for more complete information about the Company and this offering.  The offering may be made only by means of a prospectus supplement and the accompanying prospectus, copies of which 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, you may get these documents for free by visiting EDGAR on the SEC website atwww.sec.gov.

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.

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]

[email protected]