PRESS RELEASE: Arena Pharmaceuticals to Continue Obesity Study After Safety Review

Arena Pharmaceuticals to Continue Obesity Study After Safety Review

SAN DIEGO, Sept. 11 -- Arena Pharmaceuticals announced today that an independent Echocardiographic Data Safety Monitoring Board (the Board or EDSMB) found no reason to stop the ongoing pivotal Phase 3 trial, BLOOM (Behavioral modification and Lorcaserin for Overweight and Obesity Management). The BLOOM trial is evaluating the efficacy and safety of lorcaserin hydrochloride for the treatment of obesity. The findings of the Board were based on a planned detailed review of unblinded echocardiograms performed after patients completed six months of dosing in the trial. The review was conducted by the Board and confirms that differences, if any, in the rates of U.S. Food and Drug Administration (FDA)-defined valvulopathy in patients treated with lorcaserin and in the control group did not meet predetermined stopping criteria. The review also confirmed that the rate of FDA-defined valvulopathy in the placebo group is consistent with the company's statistical powering assumptions used in the design of the pivotal trial program to monitor patients for any increased risk of developing valvulopathy. Arena is currently in discussions with the FDA to finalize protocols for two additional Phase 3 pivotal trials scheduled to begin later this year.

"Patient safety is and always has been a primary focus for Arena in our effort to fully explore and understand lorcaserin's profile and its potential to safely help a significant number of patients that are obese or overweight improve their health by better managing their weight," said Jack Lief, Arena's President and Chief Executive Officer. "The continuation of the trial is an important milestone in that effort as we proceed with our extensive Phase 3 development program, including two additional pivotal studies evaluating lorcaserin's potential as a safe and effective treatment option for weight loss. We are also looking forward to additional support of lorcaserin's emerging safety profile through the upcoming month 12 EDSMB review in the first quarter of 2008."

BLOOM is a double-blind, randomized, placebo-controlled trial involving nearly 3,200 patients in approximately 100 centers in the United States. The trial is evaluating a 20 mg daily dose (10 mg dosed twice daily) of lorcaserin versus placebo over a two-year treatment period in obese patients (BMI 30 to 45) with or without co-morbid conditions and overweight patients (BMI 27 to 30) with at least one co-morbid condition. The primary efficacy endpoint is the proportion of patients with a 5% or greater weight reduction from baseline at week 52 as compared to placebo. In an effort to perform a thorough safety analysis of the study, patients received echocardiograms at screening and 6 months after initiating dosing in the trial, and will receive follow-up echocardiograms at 12, 18 and 24 months. As with the month 6 echocardiogram analysis, the EDSMB will review the month 12 echocardiographic data and, based upon predetermined criteria, will make a judgment as to whether it is appropriate to continue or stop the trial.

The complete lorcaserin program includes two Phase 3 pivotal trials in addition to BLOOM that are scheduled to start later this year. Under the protocols being finalized with the FDA, the two additional pivotal trials are expected to evaluate daily doses of 20 mg and 10 mg versus placebo over a one-year treatment period, with one of the trials evaluating patients with type 2 diabetes. Diet and exercise will be part of each of the pivotal trials in accordance with FDA guidance. Also, Arena has proposed to the FDA to continue conducting patient echocardiograms in these additional pivotal studies. Expanding the echocardiogram program beyond the BLOOM trial is prudent as part of the effort to establish a robust database to thoroughly evaluate and understand lorcaserin's safety profile.

"There is a clear need for novel, safe and effective treatment options to address the growing problem of obesity, which poses a serious long-term threat to the health and welfare of tens of millions of people in the United States alone, including the majority of people with type 2 diabetes," said William R. Shanahan, M.D., Arena's Vice President and Chief Medical Officer. "This safety review of the lorcaserin echocardiographic data allows for continued development of this promising compound, which seeks to address weight loss by selectively stimulating a specific area of the brain associated with the control of satiety and metabolism. I am hopeful that future data will prove this approach to be the type of additional tool we need in the fight against obesity."

Scheduled Conference Call

Arena will host a conference call and webcast to discuss the results, and to provide a corporate update today, Tuesday, September 11, 2007 at 8:30 a.m. Eastern Time (5:30 a.m. Pacific Time). Jack Lief, President and Chief Executive Officer, Dominic P. Behan, Ph.D., Senior Vice President and Chief Scientific Officer and William R. Shanahan, M.D., Vice President and Chief Medical Officer will host the conference call.

The conference call may be accessed by dialing 800.901.5247 for domestic callers and 617.786.4501 for international callers. Please specify to the operator that you would like to join the "Lorcaserin BLOOM trial update." The participant code for the call is 56686107. The conference call will be webcast live under the investor relations section of Arena's website at http://, 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 Lorcaserin

Lorcaserin, Arena's orally administered, internally discovered drug candidate for the treatment of obesity, is in an ongoing Phase 3 program. The compound stimulates the 5-HT2C serotonin receptor, located in the hypothalamus, an area of the brain associated with the control of satiety and metabolism. Results from a Phase 2 study demonstrated that treatment with lorcaserin produced highly statistically significant, progressive and dose-dependent weight loss over a 12-week period. Lorcaserin was generally well tolerated at all doses and had no apparent effects on heart valves or pulmonary artery pressure.

About Obesity

Obesity affects tens of millions of people in the United States and poses a serious long-term threat to their health and welfare. The number of overweight and obese people has substantially increased over the past several decades. Approximately two-thirds of all adults in the United States are obese or overweight, and medical and related costs of obesity were more than $123 billion in 2001. Being obese or overweight is associated with increased risk of a number of conditions, including heart disease, stroke, diabetes, cancer and osteoarthritis. Medical treatment options for obese and overweight people currently are limited.

About Arena Pharmaceuticals

Arena is a clinical-stage biopharmaceutical company focused on discovering, developing and commercializing oral drugs in four major therapeutic areas: cardiovascular, central nervous system, inflammatory and metabolic diseases. Arena's most advanced product candidate, lorcaserin, is being investigated in a Phase 3 clinical trial program for the treatment of obesity. Arena's broad pipeline of novel compounds targeting G protein-coupled receptors, an important class of validated drug targets, includes compounds being evaluated independently and with its partners, Merck & Co., Inc. and Ortho-McNeil Pharmaceutical, Inc.

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 continuation of the Phase 3 BLOOM trial and development of lorcaserin, the significance of such continuation, the significance of the review of echocardiographic data, the timing of the EDSMB's month 12 review of echocardiographic data, the rate of valvulopathy in the BLOOM placebo group, the timing, number, protocol, design, scope and other aspects of lorcaserin trials, the thoroughness of the expected database of lorcaserin data in evaluating and understanding lorcaserin, the growth and impact of obesity, the need for novel, safe and effective treatment options to address obesity, the ability of lorcaserin to fulfill such need, the ability of data to support the use of lorcaserin, the tolerability, side effects, efficacy and potential of lorcaserin, the breadth of Arena's pipeline, and about Arena's strategy, preclinical and internal and partnered clinical programs, and ability to develop compounds and commercialize drugs. 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, Arena's planned clinical trials may not proceed at the time Arena expects or at all, the results of preclinical studies or clinical trials may not be predictive of future results, Arena's ability to partner lorcaserin, APD125, APD791 or other of its compounds or programs, the timing, success and cost of Arena's research, out-licensing endeavors and clinical trials, Arena's ability to obtain additional financing, Arena's ability to obtain and defend its patents, 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 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.