"A Study of a Deuterated Psilocin Analog (CYB003) in Humans With Major Depressive Disorder"

Inclusion Criteria: Participants must meet all the following criteria to be included in the trial: * Aged 18 to 85 years inclusive, at Screening * Participant has a diagnosis of MDD (single or recurrent episode as defined by DSM-5 TR \[if single episode, duration of ≥4 weeks and ≤24 months\] and established as per evaluation by the Investigator. The first MDD episode must have occurred prior to age 60. * Depression is of moderate to severe degree at Screening and Baseline, independently confirmed by additional clinical assessments * Participant has been on a stable dose of a single antidepressant medication at an adequate dose (label specified) for an adequate duration in the last month prior to Screening and has had an inadequate response (less than 50% improvement), as judged by the Investigator. * Participant has a body mass index (BMI) of 40 kg/m2 or less (BMI ≤ 40 kg/m2), inclusive, at Screening. * Participant is able to refrain from nicotine use during the dosing session (up to 8 hours) * Registered with a healthcare professional who can confirm the diagnosis and previous treatments received by the participant. * Participants capable of producing sperm must use a condom plus spermicide during the trial and for 12 weeks after their final dose of trial medication, if their partner is a person of childbearing potential. * Participants of childbearing potential who have a partner capable of producing sperm must agree to use a highly effective method of contraception (i.e.…