Arena Pharmaceuticals Announces Agreement to Sell Common Stock

Arena Pharmaceuticals, Inc.

today announced that it has sold 21,000,000 shares of common stock to Jefferies LLC and Piper Jaffray & Co. as underwriters for its previously announced public offering. The underwriters offered the shares to purchasers in transactions on The NASDAQ Global Select Market, in the over-the-counter market, through negotiated transactions or otherwise at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices. The offering is expected to close on or about January 26, 2015, subject to customary closing conditions. In addition, Arena has granted the underwriters a 30-day option to purchase up to an aggregate of 3,000,000 additional shares of common stock. All of the shares are being offered by Arena. Arena anticipates using the net proceeds from the offering for the clinical and preclinical development of drug candidates, for discovery research for new drug candidates, and for general corporate purposes, including working capital, costs associated with product sales and manufacturing services, capital expenditures and potentially for the commercialization of any new approved drugs. Jefferies LLC and Piper Jaffray & Co. are acting as joint book-running managers for the offering. A registration statement relating to the shares described above was previously filed with the Securities and Exchange Commission (SEC) and is effective. A preliminary prospectus supplement related to the offering has been filed with the SEC and is available on the SEC's website located at http://www.sec.gov. Copies of the final prospectus supplement and the accompanying prospectus relating to this offering, when available, may be obtained from Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, 12th Floor, New York, NY 10022, by telephone at (877) 547-6340, or by e-mail at Prospectus_Department@Jefferies.com; or Piper Jaffray & Co., Attention: Prospectus Department, 800 Nicollet Mall, Suite 800, Minneapolis, MN 55402, by telephone at (800) 747-3924, or by email at prospectus@pjc.com. This press release shall not constitute an offer to sell or the solicitation of an offer to buy these securities, nor shall there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or other jurisdiction.