A Trial to Test the Safety and Tolerability of Lu AH69593 in Adults That Are Healthy or Have Narcolepsy

Key Inclusion Criteria:

For all participants in any trial Part (A, B, C and D):

• The participant has a resting supine pulse ≥45 and ≤100 beats per minute (bpm) at the Screening Visit and at the Baseline Visit.

Specifically for participants in trial Part A, B, and D:

• The participant has a body mass index (BMI) ≥18.5 and ≤30 kilograms (kg)/square meter (m^2) at the Screening Visit.
• The participant has a normal circadian rhythm, defined as a person who usually wakes up between 6:00 and 9:00 a.m. and goes to sleep between 9:00 p.m. and midnight.
• The participant is ≥18 and ≤55 years of age at the Screening Visit.

Specifically for participants in trial Part C:

• The participant has a BMI ≥18.5 and ≤35 kg/m^2 at the Screening Visit.
• The participant has NT1, diagnosed according to International Classification of Sleep Disorders, 3rd edition criteria, with a history of disease diagnosis >3 months prior to the Screening Visit.
• The participant is ≥18 and ≤64 years of age at the Screening Visit.

Key Exclusion Criteria:

For all participants in any trial Part (A, B, C and D):

• The participant has previously been enrolled in this trial.
• The participant has previously been dosed with Lu AH69593.
• The participant has participated in a clinical trial <30 days prior to the Screening Visit.
• The participant is pregnant, breastfeeding, intends to become pregnant, or is of childbearing potential and not willing to use adequate contraceptive methods.
• The participant has a history of cancer, other than basal cell or Stage 1 squamous cell carcinoma of the skin or adequately treated cervical intraepithelial neoplasia, that has not been in remission for >5 years prior to the first dose of investigational medicinal product (IMP).
• The participant has worked shifts, including night duty, or has travelled across >3 time zones <2 weeks prior to the first dose of IMP.
• The participant trains/exercises intensively, for example, for a marathon or triathlon, or at a competitive level.

Specifically for participants in trial Part A, B and D:

• The participant has had a clinically significant illness from which he/she recovered <4 weeks prior to the first dose of IMP.

Specifically for Participants in trial Part B and C:

• The participant is at significant risk of suicide based on medical history, mental status, investigator judgement, or the C-SSRS answer of 'yes' to suicidal ideation question 4 or 5 or 'yes' to suicidal behaviour, within the last 6 months on the C-SSRS at the Screening Visit or 'Since last visit' at the Baseline Visit Day -1.

Specifically for participants in trial Part C:

• The participant has any other disorder for which the treatment takes priority over treatment of narcolepsy or is likely to interfere with trial treatment or impair treatment compliance.
• The participant has a current medical disorder, other than NT1, associated with excessive daytime sleepiness (EDS).

Note: Other protocol-defined inclusion and exclusion criteria may apply.