Actelion says its experimental sleep therapy has performed well in a clinical trial, raising the prospects of a new class of sleep drugs that inhibit orexin, a chemical in the brain believed to keep people awake. The news hits as a variety of Big Pharma players are angling to introduce new sleep meds. Ambien, a blockbuster in the field, has just gone generic. And there's a widespread belief that a new drug can appeal to consumers who don't respond to nonbenzodiazepine drugs. At the World Sleep Congress in Cairns, Australia, Actelion said that almorexant significantly increased sleep time when compared with a placebo. A late-stage trial should get underway by the end of this year.