Arena Pharmaceuticals, Inc.
Aug 3, 2010

Arena Pharmaceuticals Announces Second Quarter 2010 Financial Results and Recent Developments

FDA Completes Successful Pre-Approval Inspection of Arena's Swiss Manufacturing Facility

San Diego, CA, August 3, 2010 - Arena Pharmaceuticals, Inc. (NASDAQ: ARNA) today reported financial results for the second quarter ended June 30, 2010, and recent developments, including the successful Pre-Approval Inspection, or PAI, of the company's Swiss drug product manufacturing facility by the US Food and Drug Administration, or FDA.

"We have recently achieved a number of important milestones, including the establishment of an agreement with Eisai for the commercialization of lorcaserin in the US, the successful completion of the FDA's pre-approval inspection of our Swiss manufacturing facility and the publication of our BLOOM trial results in the New England Journal of Medicine," stated Jack Lief, Arena's President and Chief Executive Officer. "We are continuing to execute on our plans for lorcaserin as we prepare for the September FDA advisory committee meeting and potential regulatory approval."

Arena reported a lower net loss in the second quarter of 2010 of $28.8 million, or $0.28 per share, compared to a net loss in the second quarter of 2009 of $38.0 million, or $0.48 per share, and a lower net loss in the first half of 2010 of $60.0 million, or $0.60 per share, compared to a net loss in the first half of 2009 of $88.6 million, or $1.16 per share.

As expected, research and development expenses declined to $20.5 million in the second quarter of 2010 from $24.2 million in the second quarter of 2009. Research and development expenses in the first half of 2010 declined to $38.8 million from $66.8 million in the first half of 2009. This decrease is primarily attributable to the completion of the pivotal Phase 3 clinical trials for lorcaserin. Research and development expenses included $1.8 million in non-cash, share-based compensation expense in the first half of both 2010 and 2009. General and administrative expenses totaled $6.8 million in the second quarter of 2010, compared to $5.7 million in the second quarter of 2009, and $13.8 million in the first half of 2010, compared to $13.3 million in the first half of 2009. This increase in general and administrative expenses is primarily attributable to increased market research expenses. General and administrative expenses in the first half of 2010 included $1.3 million in non-cash, share-based compensation expense, compared to $1.6 million in the first half of 2009. Interest expense of $9.9 million was recorded in the first half of 2010, compared to $3.7 million in the first half of 2009. This increase is primarily attributable to the loan Arena received from Deerfield Management in July 2009.

At June 30, 2010, cash, cash equivalents and short-term investments totaled $118.5 million and approximately 112.3 million shares of common stock were outstanding. In July 2010, Arena received an upfront payment of $50.0 million from Eisai Inc., or Eisai, under a marketing and supply agreement for lorcaserin.

Arena's Recent Developments

2010 Financial Guidance

Arena reported that it expects to end 2010 with $112 million to $122 million in cash, cash equivalents and short-term investments, reflecting receipt in July 2010 of the $50 million upfront payment from Eisai, and also increased revenue guidance from a range of $12 million to $14 million to a range of $14 million to $16 million to reflect the 2010 amortization of such upfront payment. Both cash and revenue guidance excludes any potential milestones from Eisai and other existing collaborations, revenue from any new collaborations in 2010 and any commercial sales of lorcaserin. Arena decreased its 2010 guidance for general and administrative expenses from a range of $31 million to $35 million to a range of $26 million to $30 million (including non-cash expenses of approximately $3 million) primarily to reflect lower anticipated marketing costs for lorcaserin. Arena reiterated the following other components of its full year guidance: external clinical and preclinical study fees and expenses, including manufacturing, of approximately $17 million to $21 million; internal research and development expenses of approximately $57 million to $63 million (including non-cash expenses of approximately $10 million); and capital expenditures of approximately $7 million.

Scheduled Earnings Call

Arena will host both a conference call and webcast to discuss the second quarter 2010 financial results and to provide a business and financial update today, Tuesday, August 3, 2010, at 5:00 p.m. Eastern Time (2:00 p.m. Pacific Time). Jack Lief, President and Chief Executive Officer, and Robert E. Hoffman, Vice President, Finance and Chief Financial Officer, will host the conference call.

The conference call may be accessed by dialing 877.643.7155 for domestic callers and 914.495.8552 for international callers. Please specify to the operator that you would like to join the "Arena Pharmaceuticals' Second Quarter 2010 Conference Call." The conference call will be webcast live under the investor relations section of Arena's website at www.arenapharm.com, 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 broadcast to ensure adequate time for any software download that may be necessary.

About Arena Pharmaceuticals

Arena is a clinical-stage biopharmaceutical company focused on discovering, developing and commercializing oral drugs that target G protein-coupled receptors, an important class of validated drug targets, in four major therapeutic areas: cardiovascular, central nervous system, inflammatory and metabolic diseases. Arena's most advanced drug candidate, lorcaserin, is intended for weight management and has completed a pivotal Phase 3 clinical trial program. Arena has filed an NDA for lorcaserin, and the FDA has assigned a PDUFA date of October 22, 2010, for review of the application. Arena's wholly owned subsidiary, Arena Pharmaceuticals GmbH, has granted Eisai Inc. exclusive rights to market and distribute lorcaserin in the United States.

Arena Pharmaceuticals® and Arena® are registered service marks of the company. "APD" is an abbreviation for Arena Pharmaceuticals Development.

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 the significance of the marketing and supply agreement with Eisai, the FDA's pre-approval inspections, and the publication of BLOOM trial results; rights and obligations under the marketing and supply agreement with Eisai and expectations, goals and future activities related to such agreement; the September 2009 FDA advisory committee meeting; the advancement, therapeutic indication and use, safety, efficacy, tolerability, potential, regulatory review and potential regulatory approval and commercial launch of lorcaserin; the significance of biomarkers; financial guidance; and Arena's focus, goals, strategy, research and development programs, and ability to develop compounds, commercialize drugs and execute its plans. 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, risks related to the implementation and continuation of the marketing and supply agreement with Eisai and dependence on Eisai for commercialization of lorcaserin in the United States; regulatory authorities or advisors may not find data from Arena's clinical trials and other studies sufficient for regulatory approval; the timing and ability of Arena to receive regulatory approval for its drug candidates; the ability to enter into agreements to develop or commercialize lorcaserin and other of Arena's compounds or programs; Arena's ability to commercialize lorcaserin outside of the United States with another company or independently; the timing, success and cost of the lorcaserin program and other of Arena's research and development programs; results of clinical trials and other studies are subject to different interpretations and may not be predictive of future results; clinical trials and other studies may not proceed at the time or in the manner Arena or others expect or at all; Arena's ability to obtain adequate funds; Arena's ability to obtain and defend its patents; and the timing and receipt of payments and fees, if any, from Eisai and 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 filings with the Securities and Exchange Commission. These forward-looking statements represent Arena's judgment as of the time of this release. Arena disclaims any intent or obligation to update these forward-looking statements, other than as may be required under applicable law.

Contact:

Arena Pharmaceuticals, Inc.
Jack Lief
President and CEO

Cindy McGee
Manager, IR and Corporate Communications
858.453.7200, ext. 1479

Media Contact:

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David Schull, President
david.schull@russopartnersllc.com
858.717.2310

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212.845.4251