ELE-101 Safety & Tolerability Study in Healthy Participants and Patients With Depression

Inclusion Criteria: * Healthy male or female participants aged 18 to 65 years, inclusive. * Participants have a body mass index (BMI) of 18 to 35 kg/m2, inclusive. * Participants are able and willing to give written informed consent, adhere to the compliance terms during participation in the study, undergo the examinations and testing set forth in the study Protocol and clearly and reliably communicate their subjective symptoms to the Investigator. * Part 2 Only: Patient has a diagnosis of MDD and is not on antidepressant medication. Exclusion Criteria: * Current, or history (within the last 6 months) of, alcohol or substance use disorder. * Use of pharmacological compounds for psychiatric or neurological conditions acting on the CNS within 30 days or 5 half-lives (whichever is longer) prior to Screening. * Current or clinically relevant history of schizophrenia, psychotic, bipolar disorder, delusional disorder, paranoid personality disorder, schizoaffective disorder, borderline personality disorder or panic disorder. * In first-degree relatives, a history of schizophrenia, psychosis, bipolar disorder, delusional disorder, paranoid personality disorder or schizoaffective disorder. * History of a diagnosis of Hallucinogen Persistent Perceptual Disorder (HPPD). * Significant suicide risk. * Other personal circumstances and behavior that is incompatible with establishment of rapport or safe exposure to psilocin, as judged by the Investigator. * Part 1 Only: Ongoing current MDD, or history of MDD within the last year.