The drug being tested in this study is called danavorexton. The study will look at the safety, tolerability, pharmacokinetic (PK), and pharmacodynamics (PD) effects of danavorexton.~The study will enroll approximately 18 participants (to acquire data in 'n' greater than or equal to [>=] 12). Each participant will receive one of the following treatments in each Treatment Period: Danavorexton low dose (LD), danavorexton high dose (HD), or placebo. All participants will receive all 3 treatments. A washout period of a minimum of 2 days up to 14 days will be maintained between the end of infusion to the start time of next infusion. The order in which each participant receives the 3 treatments will be randomly assigned. Treatment order will remain undisclosed to the participants and study doctor during the study (unless there is an urgent medical need).~This single-center trial will be conducted in Australia. The overall time to participate in this study is up to 69 days. Participants will be followed remotely until 5 to 9 days after the last dose of study drug in the Treatment Period 3.
The main aim of the study is to check the side effects from overnight treatment with danavorexton and assess the tolerability of varying doses of danavorexton administered intravenously.~Before starting treatment with danavorexton, participants will keep a sleep diary and use an under-mattress sensor for at least 7 nights to check regular sleep habits.~There will be 3 Treatment Period up to 14 days apart. In each Treatment Period, participants will receive an intravenous (through the vein) infusion of either danavorexton or a placebo starting in the evening and continuing over a 10-hour period. A placebo looks exactly like danavorexton but does not have any medicine in it.~Participants will take part in a follow-up phone appointment about a week after the last Treatment Period.