Study to Evaluate the Absorption, Distribution, Break Down and Elimination and the Safety of 14C-Labeled Tozadenant

Inclusion Criteria: * Subject is a male between the ages of 18 and 55 years inclusive; subject may be of any racial group * Subject is informed and given ample time and opportunity to think about his participation and has signed and dated the Independent Ethics Committee (IEC) approved written Informed Consent form * Subject is considered reliable and capable of adhering to the protocol, according to the judgment of the Investigator, and is capable of communicating satisfactorily with the Investigator and complying with all study requirements * Subject has a body mass index (BMI) between 18 to 30 kg/m², inclusive, and weighs at least 50 kg * In the opinion of the Investigator, determined on the basis of the medical history and a general clinical examination at Screening, the subject has no clinically relevant cardiovascular, renal, gastrointestinal, hepatic, metabolic, endocrine, neurological or psychiatric abnormalities, and the subject is in general good health * Subject is a nonsmoker, or has stopped smoking for at least 3 months prior to the Screening Visit * Subject has clinical laboratory test results within the reference ranges of the laboratory. Subjects with isolated laboratory test results that are outside the reference ranges will be allowed to enroll at the discretion of the Investigator, so long as these results are deemed by the Investigator to be clinically nonsignificant * Subject has Blood Pressure (BP) and pulse rate within normal range in supine position after 5 minutes rest (SBP: 90 to 140 mmHg, DBP: 50 to 90 mmHg, pulse rate: 45 to 100 bpm). Subjects with vital sign results that are outside the specified ranges and that are deemed clinically nonsignificant will be allowed to enroll at the discretion of the Investigator * Subject has regular intestinal transit, in the opinion of the Investigator, determined on the basis of absence of any history or current symptoms of recurrent constipation, diarrhea, or any other gastrointestinal diseases. The mean stool frequency should be at least once every 2 days * Subject confirms that, during the study period and for a period of 3 months after the final dose, when having sexual intercourse with a woman of childbearing potential, he will use a barrier contraceptive (eg, condom) AND that the respective partner will use an additional contraceptive method. Subject should also agree not to donate semen during this period of time Exclusion Criteria: * Subject has previously participated in this study or another tozadenant study * Subject is currently participating in or has participated in another study of an investigational medicinal product or medical device in the last 3 months or 5 half-lives (whichever is longer) * Subject has a history of exposure to ionizing radiations (except radiography) or has participated in another Absorption, Distribution, Metabolism, and Excretion (ADME) study with a radiation burden \>0.1 mSv in the period of 1 year before Screening * Subject has a history of, or present, medical or psychiatric condition that, in the opinion of the Investigator, could jeopardize or would compromise the subject's ability to participate in this study * The subject has a known hypersensitivity to any components of the tozadenant formulation or to similar drugs (A2a antagonists), or has a history of drug or other relevant allergy that, in the opinion of the Investigator or UCB Study Physician, contraindicates their participation * Subject has a known clinically relevant allergy or known severe adverse reaction to any drug, or known or suspected clinically relevant drug hypersensitivity that, in the opinion of the Investigator, could jeopardize or would compromise the subject's ability to participate in this study * Subject has a history or presence of drug or alcohol dependency or tests positive for drugs or alcohol (urine tests) at Screening or Day -1 * Subject consumes more than 28 units of alcohol per week (330 mL of 5% alcohol by volume beer=2 units; 125 mL of 12% wine=1.5 units; 50 mL of 40% spirits=2 units). * Subject consumes more than 600 mg of caffeine/ day (1 cup of coffee contains approximately 100 mg of caffeine, 1 cup of tea contains approximately 30 mg of caffeine, and 1 glass of cola contains approximately 20 mg of caffeine) * Subject has a diet that deviates notably from the "normal" amounts of protein, carbohydrate, and fat, as judged by the Investigator (eg, vegans) * Subject has received any prescription or nonprescription medicines, including enzyme inhibitors or inducers, over-the-counter remedies, vitamins outside the recommended daily dose limits, herbal, and dietary supplements (including St. John's Wort) within 14 days or 5 half-lives (whichever is longer) prior to administration of study medication. Occasional paracetamol use is allowed within the 14 days before the study drug administration, with a maximal dose of 2 g/day and a maximal cumulative dose of 10 g per 14 days, and during the study for the treatment of mild symptoms (eg, headache or pain relief) * Subject has consumed any grapefruit, grapefruit juice, grapefruit containing products, or star fruit within 14 days prior to the planned administration of the study drug * Subject tests positive for human immunodeficiency virus (HIV) -1/2 antibody (HIV-1/2 Ab), hepatitis B surface antigen (HBsAg), or hepatitis C antibody (HCV-Ab). * Subject has a history or present condition of hepatic disorders, including but not limited to elevation of liver enzymes (alanine aminotransferase \[ALT\], aspartate aminotransferase \[AST\], alkaline phosphatase, and gamma-glutamyltransferase \[GGT\]) at the upper limit of laboratory reference ranges * Subject has a history of thyroid abnormalities * Subject has had significant blood loss or has donated or received 50 mL or more of blood within 60 days prior to drug administration, or has donated plasma or platelets within 14 days prior to first drug administration for this study * Subject shows any sign of orthostatic hypotension at Screening, defined as: * A ≥20 mmHg decrease in SBP, and/or ≥10 mmHg decrease in DBP if the resultant SBP falls below 90mmHg and/or DBP falls below 60 mmHg. Blood pressure and pulse rate will be recorded after 5 minutes of rest in the supine position and after 2 minutes of rest in the standing position * A ≥40 mmHg decrease in SBP, and/or ≥20 mmHg decrease in DBP, regardless of resultant SBP and/or DBP. Blood pressure and pulse rate will be recorded after 5 minutes of rest in the supine position and after 2 minutes of rest in the standing position * Subject has an abnormality in the 12-lead ECG at Screening that results, in the opinion of the Investigator, in an increase in the risks associated with participating in the study. In addition, any subject with any of the following findings will be excluded: * QT interval corrected for heart rate using Fridericia's formula (QTcF) \>450 ms in ECG * Bundle branch blocks and other conduction abnormalities other than mild first degree atrioventricular block (defined as PR interval ≥220 ms) * Irregular rhythms other than sinus arrhythmia or occasional, rare supraventricular or ventricular ectopic beats * In the judgment of the Investigator, T-wave configurations are not of sufficient quality for assessing QT interval duration * Subject has a history of unexplained syncope, or a family history of unexplained sudden death or sudden death due to long QT syndrome * Subject has a history or present condition of respiratory or cardiovascular disorders (eg, cardiac insufficiency, coronary heart disease, hypertension, arrhythmia, tachyarrhythmia, or myocardial infarction) * Subject has a history or present condition of malignancy, gastrointestinal bleeding, or anal fissures * Subject is unable to understand the constraints of full urine and stool collection