Arena issued patent for 5-HT2A receptor modulators.

Arena Pharmaceuticals, Inc. (San Diego, CA) was granted EP Patent 1558582, entitled "Diaryl and Arylheteroaryl Urea Derivatives as Modulators of the 5-HT2A Serotonin Receptor Useful for the Prophylaxis and Treatment of Disorders Related Thereto," by the European Patent Office. The patent relates to a class of inverse agonists to the 5-HT2A serotonin receptor, which is thought to be involved in the regulation of sleep architecture and sleep maintenance. These inverse agonists may be useful in pharmaceutical compositions for the treatment of insomnia. APD125, discovered by Arena, is an orally available 5-HT2A receptor modulator covered under the patent. Arena intends to validate the patent in 31 European jurisdictions, including Germany, France, Italy, the United Kingdom and Spain.

On June 30, 2005, Arena announced top-line results from its Phase 1 clinical trial program, which indicated that APD125 was well tolerated at all doses investigated and demonstrated a robust (60%) and statistically significant (p=0.0002) increase in the amount of deep, or slow wave, sleep in volunteers with normal sleep/wake patterns. An ongoing evaluation of the Phase 1 APD125 data has provided additional statistically significant signals (p is less than or equal to 0.05) indicative of improved sleep maintenance. Among the new data are statistically significant increases in stage 3 and stage 4 sleep, reductions in stage 1 sleep, reductions in the number of awakenings, and an increase in delta power during slow wave sleep. The ongoing evaluation also continues to support the encouraging preliminary safety and tolerability profile of APD125.

Arena intends to begin dosing chronic insomniacs in a Phase 2 clinical trial of APD125 in early 2006 under an investigational new drug, or IND, application being reviewed by the FDA. Arena expects results from the Phase 2 clinical trial around the middle of 2006.

"APD125 represents a promising new approach to the treatment of insomnia, and we look forward to the Phase 2 results," commented Jack Lief, Arena's President and Chief Executive Officer. "APD125, like our obesity drug candidate APD356, was discovered by Arena. Also like APD356, it is unpartnered and directed at a major pharmaceutical market opportunity."

Insomnia is characterized by inadequate or poor sleep due to nonrefreshing sleep, frequent awakenings with difficulty falling back to sleep, difficulty falling asleep or awaking too early. Most insomnia complaints relate to sleep maintenance issues, such as awaking frequently or awakening too early, as opposed to problems with sleep latency (i.e., falling asleep). About 30 to 40 percent of United States adults complain about some level of insomnia in the course of a year, and about 10 to 15 percent of United States adults indicate that their condition is severe or chronic. Generally, insomnia is termed chronic when it persists for at least one month, and acute when lasting for one or several days. The prevalence of insomnia increases with age and is more common in women.

Insomnia has a variety of causes. It is often a symptom of some other disease or condition (e.g., life stress, psychiatric and medical disorders, or use of certain medications), but it can also be a distinct disorder. Common symptoms of acute insomnia are sleepiness, negative mood and impairment of performance. Chronic insomnia is often associated with fatigue, mood changes, difficulty concentrating and impaired daytime functioning.

Discovered by Arena, APD125 is a novel and orally bioavailable, highly selective inverse agonist of the 5-HT2A serotonin receptor. Marketed drugs for insomnia that activate GABA-A receptors in the brain trigger a general central nervous system, or CNS, suppressive effect. These drugs are DEA-scheduled controlled substances due to their potential for abuse. Common side effects of GABA activating drugs include the risk of developing tolerance to the drug, impaired functioning when the drug is at therapeutic levels, and the potential for causing a sensation of dullness and lethargy upon awakening, often referred to as the "hangover effect."

By selectively targeting the 5-HT2A receptor, APD125 acts through a different mechanism than currently marketed insomnia drugs, inhibiting one of several CNS activating pathways rather than generally suppressing the CNS. Because of the different mechanism of action, APD125 may not have the side effects generally associated with currently marketed GABA-A drugs. APD125 has the potential to reduce insomnia symptoms and improve sleep maintenance by decreasing the number of awakenings during the night, decreasing the amount of wake time after initial sleep onset, and increasing the amount of time spent in deep sleep, or slow wave sleep (stage 3 and stage 4 sleep), the most restorative type of sleep.

Arena is a clinical-stage biopharmaceutical company focusing on the discovery, development and commercialization of small molecule 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, using its knowledge of GPCRs and its technologies, including CART (Constitutively Activated Receptor Technology) and Melanophore. Arena has three internally discovered, clinical-stage product candidates. Arena's most advanced clinical compound, APD356, a selective 5-HT2C serotonin receptor agonist for the treatment of obesity, is expected to enter Phase 3 clinical development in the middle of 2006. Arena's lead product candidate for the treatment of insomnia, APD125, a compound with a novel mechanism of action (a selective 5-HT2A receptor inverse agonist), is expected to enter Phase 2 clinical development in early 2006. As part of Arena's collaboration with Merck & Co., Inc., an Arena product candidate for the treatment of atherosclerosis and related disorders is in a Phase 1 clinical trial. Arena also has an active collaboration with Ortho-McNeil, Inc., a Johnson & Johnson company, for the treatment of type 2 diabetes.

Arena Pharmaceuticals, Inc.

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www.arenapharm.com