Arena Pharmaceuticals, Inc.
Oct 20, 2003

Arena Pharmaceuticals Purchases Stock From Largest Stockholder

SAN DIEGO, Oct 20, 2003 /PRNewswire-FirstCall via COMTEX/ -- Arena Pharmaceuticals, Inc. (Nasdaq: ARNA) today announced that Biotechnology Value Fund, L.P. and certain of its affiliates accepted Arena's offer to purchase three million shares of Arena common stock from them at a cash price per share of $7.69. Arena made the offer on October 7, 2003, pursuant to the Stockholders Agreement dated as of January 17, 2003, by and among Arena and Biotechnology Value Fund, L.P., Biotechnology Value Fund II, L.P., BVF Investments, L.L.C., BVF Partners L.P., BVF Inc. and Investment 10, L.L.C. As a result of the acceptance, the standstill and certain other provisions under the Stockholders Agreement will be extended until December 31, 2004.

The Stockholders Agreement is filed as Exhibit 10 to Arena's January 21, 2003, Form 8-K.

Arena is a biopharmaceutical company focused on discovering and developing drugs that act on an important class of drug targets called G protein-coupled receptors, or GPCRs. Arena uses its Constitutively Activated Receptor Technology, or CART, Melanophore technology and other proprietary technologies to better understand GPCRs and to identify small molecules that may lead to new drugs. Arena focuses its efforts in four therapeutic areas: metabolic diseases, cardiovascular diseases, central nervous system disorders and inflammatory diseases. Within these areas, Arena is developing a portfolio of internally discovered, highly selective small molecules for large markets with unmet medical needs, including obesity, diabetes, depression and sleep disorders.

Certain statements in this press release are forward-looking statements that involve a number of risks and uncertainties. Such forward-looking statements include statements about Arena's strategy, technologies, internal programs, future achievements, and statements that are not historical facts, including statements about our ability to identify and develop small molecules or which are preceded by the word "will" or similar words. For such statements, Arena claims the protection of the Private Securities Litigation Reform Act of 1995. Actual events or results may differ materially from Arena's expectations. Important factors that could cause actual results to differ materially from those stated or implied by Arena's forward-looking statements are disclosed in Arena's SEC reports, including Arena's most recent quarterly report on Form 10-Q. These forward-looking statements represent Arena's judgment as of the date of this release. Arena disclaims any intent or obligation to update these forward-looking statements.

Arena Pharmaceuticals® and Arena® are registered service marks of the company. CART is an unregistered service mark of the company. Arena's headquarters are at 6166 Nancy Ridge Drive, San Diego, California 92121, and its telephone number is (858) 453-7200. On the Internet, please refer to Arena's Web site at www.arenapharm.com for further information.

SOURCE Arena Pharmaceuticals, Inc.

Jack Lief, President and CEO, ext. 223, or Joseph F. Mooney, CFO, ext. 508, both for Arena Pharmaceuticals, Inc., +1-858-453-7200