Arena Pharmaceuticals, Inc.
Oct 20, 2004

Arena Pharmaceuticals Announces Equity Investment by Merck and Extension and Expansion of Merck Collaboration

SAN DIEGO, Oct. 20 /PRNewswire-FirstCall/ -- Arena Pharmaceuticals, Inc. (Nasdaq: ARNA) announced today that Merck & Co., Inc. has extended and increased the funding of research under their existing cardiovascular collaboration until October 2007, and expanded the scope of the collaboration to include a wider range of potential therapies for important cardiovascular diseases.

Merck also purchased $7.5 million of Arena common stock at a price of $8.00 per share, which represents approximately a seventy percent premium to yesterday's closing price.

Under the amended collaboration, Merck will fund $5.7 million a year for collaboration research at Arena. The amendment also limits the circumstances by which Merck can terminate the research funding and improves for Arena the terms relating to royalties.

"Merck's equity investment and continued commitment to our cardiovascular collaboration is a credit to our scientists and validates our GPCR technologies," stated Jack Lief, Arena's President and Chief Executive Officer. "Over the next few years, we look forward to working synergistically with Merck to bring effective treatments for cardiovascular disease to the clinic."

"Merck is pleased with the progress the collaboration has achieved to date," says Mervyn Turner, Ph.D., Senior Vice President Worldwide Licensing and External Research. "We look forward to continuing our work with Arena in this important area."

In October 2002, Arena and Merck entered into a collaboration focused on a group of GPCR targets discovered by Arena and believed to represent novel targets for cardiovascular disease. Arena announced in the first quarter of 2004 the achievement of a $4 million milestone and in the third quarter of 2004 the achievement of a $3 million milestone under this collaboration.

Arena will host a third quarter financial results and corporate update conference call on Wednesday, October 20, 2004 at 5:00 p.m. Eastern Time (2:00 p.m. Pacific Time), during which time Arena's management will discuss the extension and expansion of this collaboration. The conference call may be accessed by dialing (888) 273-9887 for domestic callers, and (612) 332-0634 for international callers. Please specify to the operator that you would like to join the "Arena Pharmaceuticals Third Quarter Earnings Conference Call." The conference call will be webcast live on Arena's website at http://www.arenapharm.com, under the investor relations section, and will be archived there for 30 days following the call. Please connect to Arena's website several minutes prior to the start of the conference call to ensure adequate time for any software download that may be necessary.

About Arena Pharmaceuticals

Arena is a biopharmaceutical company focusing on the discovery, development and commercialization of drugs in four major therapeutic areas: metabolic, cardiovascular, inflammatory and central nervous system diseases. Arena is developing a broad pipeline of compounds that act on an important class of drug targets called G protein-coupled receptors, or GPCRs, and that are being developed using Arena's proprietary technologies, including CART (Constitutively Activated Receptor Technology) and Melanophore. Arena also has research collaborations with Merck, Fujisawa, Taisho and TaiGen for products in a number of different indications. For additional information about Arena, visit their website at http://www.arenapharm.com.

Forward-Looking Statements

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 collaboration with Merck and statements about Arena's strategy, technologies, preclinical and clinical programs, ability to identify and develop drugs, future achievements, goals and expectations, as well as other 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. Factors that could cause actual results to differ materially from the forward-looking statements include, but are not limited to, the timing, success and cost of Arena's research, out-licensing endeavors and clinical studies, Arena's ability to obtain additional financing, and the timing and receipt of payments and fees, if any, from Arena's collaborators. Additional 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.

Contacts:
Jack Lief, President & CEO
Arena Pharmaceuticals
858-453-7200

Susan Neath, Media & Investor Relations
Atkins + Associates
858-527-3486

SOURCE Arena Pharmaceuticals, Inc.
10/20/2004
Web site: http://www.arenapharm.com