Arena Pharmaceuticals Announces Public Offering of Common Stock

SAN DIEGO, July 7, 2009 /PRNewswire-FirstCall/ -- Arena Pharmaceuticals, Inc.
(Nasdaq: ARNA) announced today that it intends to offer shares of its common
stock in a public offering. Piper Jaffray & Co. will be the sole underwriter
for the offering. The offering is being made pursuant to a shelf registration
statement filed with the Securities and Exchange Commission on November 25,
2008, which became effective on December 3, 2008. A prospectus supplement
relating to the offering will be filed with the Securities and Exchange
Commission.

This press release shall not constitute an offer to sell or the solicitation
of an offer to buy, 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 jurisdiction. When available, copies of the prospectus
supplement relating to this offering may be obtained by contacting Piper
Jaffray & Co. by mail at 800 Nicollet Mall, Suite 800, Minneapolis, MN 55402
or by telephone at 800.747.3924.
Contact: Jack Lief
President and CEO

Robert E. Hoffman
VP, Finance and CFO
Arena Pharmaceuticals, Inc.
858.453.7200, ext. 222

www.arenapharm.com

SOURCE Arena Pharmaceuticals, Inc.

Jack Lief, President and CEO, or Robert E. Hoffman, VP, Finance and CFO, both
of Arena Pharmaceuticals, Inc., +1-858-453-7200, ext. 222