MK-1064 is an orexin 2 receptor antagonist patented by pharmaceutical company Merck & Co for the treatment of insomnia. MK-1064decreases the amount of time spent in active wake and increases the time spent in rapid eye movement (REM) sleep and slow-wave sleep (SMS) in mice, rats, dogs, and rhesus monkeys. MK-1064, even at the very high dose did not show signs of an enhanced predisposition to cataplexy in the food-elicited cataplexy test. MK-1064 has now completed two Phase I studies focused on pharmacokinetics, safety and sleep in healthy volunteers. The effects of MK-1064 on sleep parameters were moderate, but statistically significant, representing the first demonstration of PSG-quantified sleep induced in humans by an OX2R antagonist. MK-1064 at 50, 120 and 250 mg decreased latency to persistent sleep and wake after sleep onset, and increased total sleep time and sleep efficiency.