The purpose of this study is to evaluate the effect of clopidogrel on the pharmacokinetics of selexipag and its active metabolite (ACT-333679) in healthy male adults (by determining the blood concentrations of selexipag and its metabolite). Also, the safety of selexipag when administered alone or with clopidogrel will be assessed.

Inclusion Criteria:

• Signed informed consent in the local language prior to any study-mandated procedure.
• Healty male subjects aged between 18 and 45 years (inclusive) at screening.
• Body mass index from 18.0 to 28.0 kg/m2 (inclusive) at screening.
• Systolic blood pressure (SBP) 100-145 mmHg, diastolic blood pressure (DBP) 50-90 mmHg, and pulse rate 45-90 bpm (inclusive).

Exclusion Criteria:

• Any contraindication included in the SmPC of selexipag or clopidogrel treatment.
• History or clinical evidence of any disease and/or existence of any surgical or medical condition, which might interfere with the absorption, distribution, metabolism or excretion of the study treatments.
• History or clinical evidence of any disorder of hemostasis, hemorrhagic diathesis, nose or gingival bleeding, hemophilia, thrombotic thrombocytopenic purpura, presence of any lesions with a propensity to bleed (particularly gastrointestinal and intraocular), history of bleeding complications after surgical procedures such as tooth extraction
• Previous history of stroke, fainting, collapse, syncope, orthostatic hypotension,vasovagal reactions, head injury.
• Excessive caffeine consumption
• Nicotine consumption within 3 months prior to screening, and inability to refrain from nicotine consumption during the course of the study
• Previous treatment with any prescribed medications (including vaccines) or over the counter (OTC) medications (including herbal medicines such as St John's Wort, homeopathic preparations, vitamins, and minerals) within 2 weeks prior to first selexipag administration.
• Subjects with rare hereditary problems of galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption.
• Any circumstances or conditions, which, in the opinion of the investigator, may affect the subject's full participation in the study or compliance with the protocol.