Arena Pharmaceuticals Inc. has initiated dosing in a phase 1 clinical trial for APD125, its novel drug candidate for the treatment of insomnia and the second Arena-discovered compound to enter the clinic this year. The single-dose protocol should be completed in the second quarter of 2005.

The study will evaluate the safety, tolerability and pharmacokinetic profile of APD125 in a double-blinded, placebo-controlled, single-dose, dose-escalation trial in healthy volunteers. The study is being conducted at a leading insomnia clinical research centre in France.

"We believe APD125 represents a significant development opportunity because it targets a sleep mechanism different from existing therapies and others in late stage development," stated Jack Lief, Arena's president and CEO. "By acting through this distinct mechanism, our compound may both induce sleep and improve the quality of sleep. APD125 is our second internally discovered candidate with large market potential to enter the clinic this year, representing another important milestone for Arena in 2004," he added.

APD125 is a highly selective antagonist at the 5-HT2A serotonin receptor and is one of a series of Arena-discovered compounds that act through this receptor target. In animal studies, APD125 increases non-REM sleep, the most restorative phase of the sleep cycle, without sacrificing REM or dream sleep. Arena believes that this unique mechanism may avoid the CNS side effects observed with GABA-acting drugs.

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