Clinical results from a Phase IIb study conducted on 254 patients with primary insomnia showed positive effects for Merck’s MK-4305.

MK-4305 is Merck’s investigational dual-orexin receptor antagonist, which inhibits the actions of orexin A and orexin B – the chemical messengers important in the sleep-wake system.

The primary endpoint is improvement in sleep efficiency and the secondary endpoints are improvement in wake after sleep onset and latency to persistent sleep.

The Phase III trials showed that MK-4305 was more effective than a placebo at helping patients sleep longer on night one and at the end of four weeks of treatment.

The randomised, double-blind, placebo-controlled crossover study had been designed to evaluate the safety and efficacy of four doses of MK-4305 in patients with primary insomnia.