Investigation to Understand and Optimize Psilocybin

Inclusion Criteria: Current diagnosis of Major Depressive Disorder (MDD), with a depressive episode lasting ≥ 60 consecutive days at the time of screening, as confirmed by structured clinical interview Medically healthy, as determined by the screening physician, with no significant medical conditions that would interfere with participation or affect the safety of the subject. Exclusion Criteria: History or presence of any psychiatric or medical condition that, in the opinion of the investigator, could pose a safety risk, interfere with participation, or confound study results (e.g., bipolar disorder, psychosis, seizure disorder, or cardiovascular disease). Known family history of a psychotic disorder (e.g., schizophrenia or schizoaffective disorder) in a first-degree relative (biological parent, full sibling, or child). Current active suicidal ideation with a specific plan within the prior 2 weeks, as assessed via clinical interview and validated instrument (e.g., C-SSRS). Suicide attempt within the prior 6 months, regardless of intent or lethality. Current diagnosis of a substance use disorder Abnormal ECG at screening that may increase risk during participation (e.g., prolonged QTc, arrhythmias, or other clinically significant findings as determined by the study physician). Unwilling or unable to discontinue prescription psychotropic medications (e.g., antidepressants, antipsychotics, anxiolytics, lithium, anticonvulsants, or mood stabilizers) for the duration of study participation, including any necessary washout period as determined by the investigator. Any condition, finding, or behavior (including suspected deception or noncompliance) that, in the opinion of the investigator, renders the participant unsuitable for the study or likely to interfere with the integrity of the data or safety of the subject.