Study to Investigate the Tolerability, Safety, Pharmacokinetics, and Pharmacodynamics of ACT-389949

Inclusion Criteria: * Signed informed consent prior to any study-mandated procedure. * Healthy Caucasian male subjects aged between 18 and 45 years (inclusive) at screening. * Subjects must agree to use reliable methods of contraception. * No clinically significant findings on physical examination at screening. * Body mass index (BMI) between 18.0 and 30.0 kg/m\^2 (inclusive) at screening. * Systolic blood pressure (SBP) 100-145 mmHg, diastolic blood pressure (DBP) 50-90 mmHg, and pulse rate (PR) 45-90 bpm (inclusive) measured at screening. * 12-lead ECG without clinically relevant abnormalities, measured at screening. * Body temperature (T°) 35.5-37.5°C at screening and prior to (first) dosing. * Total and differential white blood cell (WBC) count strictly within the normal ranges at screening and on Day -1. * C-reactive protein (CRP) levels below 5 mg/L. * Hematology and clinical chemistry results (other than total and differential WBC count and CRP) not deviating from the normal range to a clinically relevant extent at screening. * Coagulation and urinalysis test results not deviating from the normal range to a clinically relevant extent at screening. * Non smokers, defined as never smoked or achieved cessation for ≥ 6 months at screening. * Negative results from urine drug screen at screening. * Subjects allowing the conduct of genetic analyses on whole blood consisting of measuring the levels of messenger ribonucleic acid (mRNA) expression of mechanistic biomarkers of N-formyl-peptide receptor 2 (FPR2) and proteins involved in inflammation. * Ability to communicate well with the investigator in the local language, and to understand and comply with the requirements of the study. Exclusion Criteria: * Known allergic reactions or hypersensitivity to any excipient of the drug formulation. * 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 drug. * Previous history of recurrent fainting, collapses, syncope, orthostatic hypotension, or vasovagal reactions. * Veins unsuitable for intravenous (i.v.) puncture on either arm. * Treatment with another investigational drug within 3 months prior to screening or having participated in more than four investigational drug studies within 1 year prior to screening. * History or clinical evidence of alcoholism or drug abuse within the 3-year period prior to screening. * Excessive caffeine consumption. * Treatment with any prescribed or over-the-counter (OTC) medications within 2 weeks prior to (first) study drug administration or five half-lives of the medication, whichever is longer. * Any history of immunosuppressive treatment. * Chronic diseases including those with recurring periods of flare-ups and remission. * History of atopic allergy (including asthma, urticaria, eczematous dermatitis). * Signs of infection (viral, systemic fungal, bacterial or protozoal) within 4 weeks prior to (first) study drug administration. * History of acute or chronic obstructive lung disease (treated or not treated). * History of subarachnoid hemorrhage or hemolytic uremic syndrome. * Interval from the beginning of the P wave to the beginning of the QRS complex (PQ/PR interval) \< 120 ms at screening. * Loss of 250 mL or more of blood, or an equivalent amount of plasma, within 3 months prior to screening. * Positive results from the hepatitis serology, except for vaccinated subjects or subjects with past but resolved hepatitis, at screening. * Positive results from the human immunodeficiency virus serology at screening. * Any circumstances or conditions, which, in the opinion of the investigator, may affect full participation in the study or compliance with the protocol. * Legal incapacity or limited legal capacity at screening.