A Study to Compare a Single-dose of Two Different Formulations of ACT-709478 in Healthy Men

• Signed informed consent in a language understandable to the subject prior to any study-mandated procedure.
• Body mass index of 18.5-28.0 kg/m2 (inclusive) at Screening.
• Czech citizen with the ability to communicate well with the investigator, in a language understandable to the subject, and to understand and comply with the requirements of the study.
• Systolic blood pressure 100 to 145 mmHg, diastolic blood pressure 60 to 90 mmHg, and pulse rate 50 to 90 bpm (inclusive) after 5 min in the supine position at Screening.
• Healthy on the basis of physical examination, cardiovascular assessments, and laboratory tests.

Exclusion Criteria:

• Known hypersensitivity to any of the excipients of the study treatment formulations.
• Participation in a clinical study involving study treatment administration within 3 months or 5 half-lives (whichever is longer) prior to Screening, or in more than 4 clinical studies within 1 year prior to Screening.
• History of major medical or surgical disorders which, in the opinion of the investigator, are likely to interfere with the absorption, distribution, metabolism, or excretion of the study treatments (appendectomy and herniotomy allowed, cholecystectomy not allowed).
• Acute, ongoing, recurrent, or chronic systemic disease able to interfere with the evaluation of the study.
• Any cardiac condition or illness with a potential to increase the cardiac risk of the subject based on medical history, physical examination, or ECG evaluations.
• History or presence of rhythm disorders (e.g., sinoatrial heart block, sick-sinus syndrome, second- or third-degree atrioventricular block, long QT syndrome, symptomatic bradycardia, atrial flutter, or atrial fibrillation).
• PR Interval on 12-lead ECG greater than 200 ms at Screening.
• Previous treatment with any prescribed medications (including vaccines) or over-the-counter medications (including herbal medicines such as St John's Wort, homeopathic preparations, vitamins, and minerals) within 2 weeks or 5 t½ (whichever is longer) prior to first study treatment administration.