Arena Pharmaceuticals, Inc.
Dec 15, 2003

Arena Pharmaceuticals Announces Successful Completion of Preclinical Studies On Its Novel Obesity Compound and Restructuring as it Prepares to Initiate Clinical Development in the First Quarter 2004

SAN DIEGO, Dec. 15 /PRNewswire-FirstCall/ -- Arena Pharmaceuticals, Inc. (Nasdaq: ARNA) today announced that it has successfully completed preclinical studies on its internally discovered compound for obesity, APD356, and remains on schedule to initiate Phase I human clinical trials in the first quarter of 2004. Arena also announced that it has restructured certain of its operations as it transitions from primarily a discovery research company to a research and development company.

Arena has discovery programs for several obesity targets and APD356 is part of Arena's lead program in this area. APD356 is a highly selective 5HT2C agonist that has been shown to reduce body weight and food intake in animal models of obesity. Targeting the 5HT2C receptor is proposed to regulate body weight by regulating satiety. Arena has now successfully completed the preclinical safety studies necessary to allow initiation of human clinical trials in early 2004.

The restructuring includes a staff reduction totaling 30 employees, or about 9% of the company's workforce, and the transfer of an additional 12 scientists from research activities to development oriented activities. The employees that were part of the reduction are eligible for severance packages that include severance pay, continuation of health insurance and outplacement services.

"In a relatively short period of time, our scientists have created a diverse pipeline of preclinical candidates, and I am excited to report that we continue to be on schedule to begin our first human clinical trials on an internally discovered compound for obesity early next year," stated Jack Lief, President and Chief Executive Officer of Arena. "We expect to maintain our world-class capabilities in research, but also need to devote substantial resources to moving our preclinical programs into development. This staff reduction and other cost-cutting measures we have implemented will enable us to direct more of our financial resources on bringing additional compounds into human clinical development."

About Arena

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 identify small molecules that may lead to new drugs. Arena concentrates its efforts in four major 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 schedule, strategy, technologies, internal programs, future achievements and statements that are not historical facts. 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 located 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.

For further information please contact: Jack Lief, President & CEO, ext. 223, or Derek Chalmers, Vice President, Research, ext. 228, both of Arena Pharmaceuticals, +1-858-453-7200.

SOURCE Arena Pharmaceuticals, Inc.

CONTACT: Jack Lief, President & CEO, ext. 223, or Derek Chalmers, Vice President, Research, ext. 228, both of Arena Pharmaceuticals, +1-858-453-7200