Regeneron Increases Size of Public Offering of Common Stock

Regeneron Pharmaceuticals, Inc.

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 $28.00 per share for the offering. Citi is serving as sole book-running manager for the offering. The offering is expected to close on October 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, NY 11220, telephone number (800) 831-9146. Alternatively, these documents are available by visiting EDGAR on the SEC website at www.sec.gov.