This Phase III, randomised, triple-blind, multicentre trial (n=240) compares single oral psilocybin 25 mg, psilocybin 5 mg, and inactive placebo in adults with Major Depressive Disorder using a Set and Setting psychosocial support protocol.
Randomised, parallel-group Phase III trial enrolling approximately 240 adults meeting DSM-5-TR criteria for major depressive disorder; participants are assigned to psilocybin 25 mg, psilocybin 5 mg, or inactive placebo under triple-blind conditions for a single dosing session.
Investigational product is given as a single oral HPMC capsule with a Set and Setting (SaS) protocol: preparatory meetings with facilitators, a 7–10 hour supervised dosing session with two facilitators, and integration sessions (≈4 hours) post-dose; outcomes assess depressive symptoms to Day 43 and durability over a 1-year follow-up.
Following the 6-week double-blind period all participants enter a 1-year follow-up with regular clinic and phone contacts for symptom, safety, and suicidality monitoring; eligible participants may receive open-label psilocybin 25 mg re-administration under SaS.
Single oral 25 mg psilocybin capsule administered with Set and Setting (SaS) protocol (preparation, 7–10 h dosing session, integration).
HPMC capsule; administered with two facilitators in SaS protocol; encouraged headphones/eyeshades; 7–10 h session.
Single oral 5 mg psilocybin capsule administered with Set and Setting (SaS) protocol.
HPMC capsule; active comparator dose.
Single oral inactive placebo (MCC 25 mg) capsule administered with Set and Setting (SaS) protocol.
Microcrystalline cellulose (MCC) 25 mg in HPMC capsule; matched appearance.