An Open-label, Adaptive Design, Positron Emission Tomography Study in Healthy Male Participants to Characterize Receptor Occupancy by MIJ821 in the Brain

Key Inclusion Criteria: * Signed informed consent must be obtained prior to participation in the study * Healthy males, aged 23 to 55 years (inclusive), and in good health as determined by past medical history, physical and neurological examination, vital signs, electrocardiogram, and laboratory tests at Screening and Baseline (whenever applicable) * At screening and at baseline (Day -1), vital signs after 3 minutes resting (in sitting position during screening and supine position during baseline) must be within the following ranges: * Body temperature (otic) from 35.0 °C to 37.5 °C, inclusive * Systolic blood pressure (BP) from 90 to 139 mmHg, inclusive * Diastolic BP from 50 to 89 mmHg, inclusive. * Pulse rate from 50 to 90 beats per minute, inclusive * Participants must weigh at least 50 kg to participate in the study and must have a body mass index (BMI) within the range of 18.0 to 29.9 kg/m² at screening. BMI = body weight (kg) / height2 (m2) * Participants must be able to communicate well with the Investigator and to comply with the requirements of the entire study, including adhering to study restrictions and visit schedule Key Exclusion criteria: * Hypersensitivity to NMDA antagonists (MIJ821 or other compounds with similar mechanism of action, like ketamine or compounds with similar chemical structure to ketamine) or to any excipients, local anesthetics, or anticoagulants used in this study. * Any significant illness, including infectious diseases, which has not r…