USAN Council Approves Nonproprietary Name Lorcaserin Hydrochloride for Arena Drug Candidate APD356

Press Release

USAN Council Approves Nonproprietary Name Lorcaserin Hydrochloride for Arena Drug Candidate APD356

USAN Council Approves Nonproprietary Name Lorcaserin Hydrochloride for Arena Drug Candidate APD356

SAN DIEGO, May 5 /PRNewswire-FirstCall/ -- Arena Pharmaceuticals, Inc. (Nasdaq: ARNA) announced today that the United States Adopted Names (USAN) Council has approved the nonproprietary name lorcaserin hydrochloride for APD356, a selective 5-HT2C serotonin receptor agonist under investigation for the treatment of obesity. Lorcaserin hydrochloride, which is orally administered and was internally discovered by Arena, is expected to enter Phase 3 clinical development in the second half of 2006.

The USAN Council, tri-sponsored by the American Medical Association, the United States Pharmacopeial Convention and the American Pharmacists Association, serves the health professions in the United States by selecting simple, informative and unique nonproprietary names for drugs by establishing logical nomenclature classifications based on pharmacological and/or chemical relationships. The USAN Council aims for global standardization and unification of drug nomenclature and related rules to ensure that drug information is communicated accurately and unambiguously, working closely with the World Health Organization's International Nonproprietary Name Programme and various national nomenclature groups.

About Lorcaserin Hydrochloride

Lorcaserin hydrochloride, formerly designated by Arena as APD356, is a selective agonist of 5-HT2C serotonin receptors, which are located in the hypothalamus, an area of the brain that plays an important role in regulating food intake and metabolism. Discovered by Arena, lorcaserin hydrochloride is intended to selectively stimulate the 5-HT2C receptor and has approximately 100-fold selectivity in vitro for the 5-HT2C receptor relative to the 5-HT2B receptor. It is hypothesized that activation of the 5-HT2B receptor is associated with the cardiac valvulopathy observed with non-selective serotonergic agents. In addition, lorcaserin hydrochloride has approximately 15-fold selectivity in vitro for the 5-HT2C receptor versus the 5-HT2A receptor. Arena believes that the 5-HT2A receptor contributes to the potential central nervous system adverse effects associated with non-selective serotonergic agents. Arena expects that the selectivity of lorcaserin hydrochloride will allow it to be dosed at a well-tolerated level that will induce clinically relevant weight loss without the cardiac valvular side effects observed with non-selective serotonergic agents previously used in the treatment of obesity.

In a randomized, double-blinded, placebo-controlled, dose-ranging, 12-week study in 469 obese patients there was a highly statistically significant (p<0.001) average weight loss of 4.0, 5.7 and 7.9 pounds at daily doses of 10 mg, 15 mg and 20 mg (10 mg dosed twice daily), respectively, in patients taking lorcaserin hydrochloride compared to 0.7 pounds for the placebo group. Lorcaserin hydrochloride was generally well tolerated at all doses investigated in the trial and there were no apparent effects on heart valves or pulmonary artery pressures. Results from chronic twelve and six-month pre-clinical toxicology studies of lorcaserin hydrochloride similarly did not demonstrate any apparent drug effect on heart valves or pulmonary vasculature.

Arena has issued patents in the U.S. and Europe covering 5-HT2C modulators that include lorcaserin hydrochloride.

About Obesity

Obesity affects tens of millions of adults and children in the U.S. 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 U.S. are obese or overweight. Medical and related costs of obesity in the U.S. were more than $117 billion in 2000. Being obese or overweight is associated with a number of conditions, including heart disease, stroke, diabetes, cancer and osteoarthritis. Medical treatment options for obese and overweight people are currently limited.

About Arena Pharmaceuticals

Arena is a clinical-stage biopharmaceutical company focusing on the discovery, development and commercialization of small molecule drugs in four major therapeutic areas: metabolic, central nervous system, cardiovascular and inflammatory diseases. Arena is developing a broad pipeline of compounds targeting an important class of drug targets called G protein-coupled receptors, or GPCRs, using its knowledge of GPCRs and its technologies, including CART™ (Constitutively Activated Receptor Technology) and Melanophore. Arena has four internally discovered, clinical-stage drug candidates for major diseases. The most advanced is lorcaserin hydrochloride (previously referred to by Arena as APD356), a selective 5-HT2C serotonin receptor agonist that is under investigation for the treatment of obesity and is expected to enter Phase 3 clinical development in the second half of 2006. Arena's lead drug candidate for the treatment of insomnia, APD125, is a compound with a novel mechanism of action (a selective 5-HT2A receptor inverse agonist) with an IND pending before the FDA for the initiation of a Phase 2 trial in patients with chronic insomnia. Arena also has two clinical-stage collaborations with major pharmaceutical companies: Merck & Co., Inc., began a Phase 1 clinical trial of an Arena-discovered drug candidate for the treatment of atherosclerosis and related disorders in the third quarter of 2005; and Ortho-McNeil, Inc., a Johnson & Johnson company, began a Phase 1 clinical trial of APD668, an Arena-discovered drug candidate for the treatment of type 2 diabetes in the first quarter of 2006.

Arena Pharmaceuticals® and Arena® are registered service marks of the company. CART™ is an unregistered service mark 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 tolerability, side effects and efficacy of lorcaserin hydrochloride, the expected clinical trials of lorcaserin hydrochloride and APD125 and other statements about Arena's strategy, technologies, 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, the FDA may not allow Arena's planned clinical trials to 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 hydrochloride, APD125 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.

Contacts: Jack Lief
President and CEO

David Walsey
Director, Corporate Communications

Arena Pharmaceuticals, Inc.
858.453.7200, ext. 1682

Carin Canale
Porter Novelli Life Sciences
Media & Investor Relations
858.527.3498

SOURCE Arena Pharmaceuticals, Inc.