A Study to Evaluate ACT-132577 in Healthy Male Subjects

Inclusion Criteria: * Signed informed consent in a language understandable to the subject prior to any study-mandated procedure; * Healthy male subjects aged between 45 and 65 years (inclusive) at screening; * Body mass index of 18.0 to 28.0 kg/m2 (inclusive) at screening; * Healthy on the basis of physical examination, cardiovascular assessments and laboratory tests. Exclusion Criteria: * Values of hepatic aminotransferase (alanine aminotransferase and/or aspartate aminotransferase) \> 3 × upper limit of normal range at screening; * Hemoglobin \< 100 g/L at screening; * Known hypersensitivity to ACT-132577 or drugs of the same class, or any excipient of the ACT-132577 drug formulation; * Known hypersensitivity or allergy to natural rubber latex; * Previous exposure to ACT-132577; * Treatment with another investigational drug within 3 months prior to screening or participation in more than 4 investigational drug studies within 1 year prior to screening; * Any circumstances or conditions, which, in the opinion of the investigator, may affect full participation in the study or compliance with the protocol; * A radiation burden of \> 0.1 milliSievert (mSv) and ≤ 1.0 mSv in the period of 1 year prior to screening; a radiation burden of ≥ 1.1 mSv and ≤ 2.0 mSv in the period of 2 years prior to screening, etc. (add 1 year per 1 mSv).