Arena Pharmaceuticals Inc. was granted patent number 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.

According to a company release, 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.

Arena's top-line results from its phase 1 clinical trial programme indicated that APD125 was well tolerated at all doses investigated and demonstrated a robust (60%) and statistically significant 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 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 US 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. 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," commented Jack Lief, Arena's president and chief executive officer.

Insomnia is characterised by inadequate or poor sleep due to non-refreshing sleep, frequent awakenings with difficulty falling back to sleep, difficulty falling asleep or awaking too early. About 30 to 40 per cent of US adults complain about some level of insomnia in the course of a year, and about 10 to 15 per cent of U.S. adults indicate that their condition is severe or chronic.

Discovered by Arena, APD125 is a novel and orally bio-available, highly selective inverse agonist of the 5-HT2A serotonin receptor.

Arena is a clinical-stage biopharmaceutical company focusing on the discovery, development and commercialisation of small molecule drugs in four major therapeutic areas: metabolic, cardiovascular, inflammatory and central nervous system diseases.