Psilocybin for Major Depressive Disorder (MDD)

Inclusion Criteria: * Adults ≥18 years old. * Able to swallow capsules. * If of childbearing potential, agree to practice an effective means of birth control throughout the duration of the study. * Meet the DSM-5-TR criteria for a diagnosis of major depressive disorder and are currently experiencing a major depressive episode of at least a 60-day duration at the time of Screening. * Have at least moderate severity of depression symptoms at Screening and Trial Baseline. Exclusion Criteria: * Participants who are pregnant, who intend to become pregnant during the trial, or who are currently nursing. * Have any of the following cardiovascular conditions: coronary artery disease, congenital long QT syndrome, cardiac hypertrophy, cardiac ischemia, congestive heart failure, clinically-relevant valvular heart disease, pulmonary hypertension, myocardial infarction, a clinically significant ECG abnormality, or tachycardia. * Have elevated blood pressure. * Have neurological conditions such as stroke, including transient ischemic attack, epilepsy, neurodegenerative disease (e.g., dementia, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, etc.), or brain tumor. * Have severe hepatic or renal impairment. * Have uncontrolled diabetes mellitus or unstable existing thyroid disorder. * Are hepatitis or HIV positive. * Have a positive urine drug test for illicit, non-prescribed, or prohibited substances. * Meet DSM-5-TR criteria for schizophrenia spectrum or other psychotic disorders, including major depressive disorder with psychotic features ,bipolar disorder (types 1 or 2), antisocial personality disorder, borderline personality disorder or moderate or severe alcohol or drug use disorder * Meet DSM-5-TR criteria for active post-traumatic stress disorder within 6 months prior to Screening. * Have a first-degree relative with schizophrenia spectrum or other psychotic disorders, or bipolar I disorder.