Arena Pharmaceuticals Announces Proposed Public Offering of Common Stock

SAN DIEGO, July 11, 2017

Citigroup, Leerink Partners, Cantor Fitzgerald & Co. and UBS Investment Bank are acting as joint book-running managers for the offering.  JMP Securities is acting as a co-manager for the offering.

The shares of common stock described above are being offered by Arena pursuant to a shelf registration statement filed by Arena with the Securities and Exchange Commission (SEC) that became automatically effective on July 11, 2017.  A preliminary prospectus supplement and accompanying prospectus relating to the offering will be filed with the SEC and will be available on the SEC's website located at http://www.sec.gov.  Copies of the preliminary prospectus supplement and the accompanying prospectus relating to the offering, when available, may be obtained from Citigroup Global Markets Inc., c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, or by telephone at (800) 831-9146; or from Leerink Partners LLC, Attention: Syndicate Department, One Federal Street, 37th Floor, Boston, MA 02110, or by telephone at (800) 808-7525 ext. 6132, or by email at syndicate@leerink.com; or from Cantor Fitzgerald & Co., Attention: Capital Markets, 499 Park Ave., 6th Floor, New York, New York 10022, or by telephone at (212) 829-7122, or by email at prospectus@cantor.com; or from UBS Securities LLC, Attention: Prospectus Department, 1285 Avenue of the Americas, New York, NY 10019, or by telephone at (888) 827-7275.

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.

About Arena Pharmaceuticals

Arena Pharmaceuticals is a biopharmaceutical company focused on developing novel, small molecule drugs with optimized receptor pharmacology designed to deliver broad clinical utility across multiple therapeutic areas.  Our proprietary pipeline includes potentially first- or best-in-class programs for which we own global commercial rights.  Our three most advanced investigational clinical programs are ralinepag (APD811) which has completed Phase 2 evaluation for pulmonary arterial hypertension (PAH), etrasimod (APD334) in Phase 2 evaluation for multiple autoimmune indications including ulcerative colitis (UC), and APD371 in Phase 2 evaluation for the treatment of pain associated with Crohn's disease.  In addition, Arena has collaborations with the following pharmaceutical companies: Eisai Co., Ltd. and Eisai Inc. (commercial stage), Axovant Sciences (Phase 2 candidate), and Boehringer Ingelheim International GmbH (preclinical candidate).

Forward-Looking Statements