A Clinical Study to Assess Next-day Driving Performance Following Administration of ACT-541468 in Middle-aged and Elderly Subjects

Inclusion Criteria General criteria: * Signed informed consent prior to any study-mandated procedure. * Male and female subjects aged between 50 and 80 years (inclusive) at Screening. * Women of childbearing potential must have a negative serum pregnancy test at Screening and a negative urine pregnancy test on Day 1 pre-dose of each treatment period. They must consistently and correctly use a highly effective method of contraception, be sexually inactive, or have a vasectomized partner. * Women of non-childbearing potential (i.e., postmenopausal, XY genotype, Turner syndrome, uterine agenesis). Study-specific criteria * Subject has a valid driving license for more than 5 years, has driven at least 3000 km/year on average in the past 2 years. * Normal visual acuity (corrected or uncorrected). Exclusion Criteria: General criteria: * Pregnant or lactating women. * Any known factor or disease that might interfere with treatment compliance, study conduct, or interpretation of the results. * History or presence of rhythm disorders * Any circumstances or conditions, which, in the opinion of the investigator, may affect full participation in the study or compliance with the protocol. Study-specific criteria: * Current or previous diagnosis of insomnia-related disorder according to the Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM-5) criteria. * History of alcoholism, drug abuse, or regular use of sedative drugs or hypnotics within 3 years prior to Screening. * History of regular alcohol consumption within 6 months of the study defined as an average weekly intake of more than 21 units or an average daily intake of more than 3 units (males), or defined as an average weekly intake of more than 14 units or an average daily intake of more than 2 units (females). One unit is equivalent to a half-pint (approx. 250 mL) of beer or 1 measure (25 mL) of spirits or 1 glass (125 mL) of wine. * Modified Swiss Narcolepsy Scale total score \< 0 at Screening or history of narcolepsy or cataplexy. * Activities that disturb the circadian rhythm (e.g., working night shift, travelling across 3 time zones) within 2 weeks before (each) study treatment.