NCT06898606 Psilocybe Cubensis Mushrooms With or Without Fluoxetine for Refractory Depression

Eligibility & Interventions

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What to Expect as a Participant

You will actively receive the study intervention — which may be a drug, biologic, device, or procedure.

Phase 1 is the earliest stage of human testing — safety and dosage are the primary focus. Visits are frequent and medical supervision is intensive. You will be among the first people to receive this treatment.

This trial targets 24 participants in total. It began in 2024-09-05 with a primary completion date of 2026-08-20.

Brief Summary

This Phase 2a pilot, exploratory, randomized, double-blind, placebo-controlled, parallel-group trial will estimate whether concurrent fluoxetine alters the antidepressant effect, acute psychedelic experience, or safety of a psychedelic-assisted psychotherapy session in adults with treatment-resistant major depressive disorder (TRD). Eligible participants (ages 25-64) have DSM-5-TR MDD, moderate-severe, MADRS ≥20, and partial response in the current episode (≥1 adequate antidepressant trial of 6-12 weeks with \<50% symptom reduction). All participants receive one dosing session with 3g of standardized Psilocybe mushrooms - with batch assay (e.g., LC-MS) to determine the amount of psilocybin and psilocin present in the sample - with manualized preparation and integration. Participants are randomized 1:1 to fluoxetine 20 mg/day or matching placebo for 4 weeks, started 2 weeks before the psychedelic session and continued 2 weeks after. Masking is quadruple (participant, care provider, investigator, outcomes assessor). The primary outcome is change in MADRS from Baseline to Week 4, assessed by a remote, blinded rater. Key secondary outcomes include response (≥50% MADRS reduction) and remission (MADRS ≤10) at Week 4, and durability at Week 6. Exploratory outcomes assess the psychedelic experience (5D-ASC, SOCQ), psychological flexibility (AAQ-10), and safety/tolerability (UKU and adverse events). Findings will be interpreted as estimates with 95% confidence intervals to inform the design of a subsequent confirmatory trial.

Eligibility Criteria

Inclusion Criteria Age: ≥25 and \<65 years. Diagnosis: Current Major Depressive Disorder (MDD), moderate to severe, per DSM-5-TR, confirmed with SCID-5. Baseline severity: MADRS ≥20 at baseline (reassessed at the pre-dose visit to confirm ongoing eligibility). Partial Response in the current episode (PRD): ≥1 adequate antidepressant trial in this episode (therapeutic dose for ≥6-12 weeks, adherence ≥80%) with \<50% symptom reduction or clinically significant residual symptoms. Clinical stability and ability to provide informed consent; willingness to comply with all study procedures (preparation, dosing session, integration, and follow-ups). Contraception: For participants with reproductive potential, negative pregnancy test and agreement to use effective contraception during the study. Exclusion Criteria Psychiatric disorders: Bipolar I/II disorder, any psychotic disorder, or current MDD with psychotic features; first-degree family history of psychotic or bipolar disorder. Suicide risk: Acute suicidal risk, e.g., active suicidal ideation with intent or plan, recent attempt, or clinical judgment requiring urgent intervention. Interacting medications: Current use of serotonergic antidepressants (SSRI/SNRI/MAOI, clomipramine) or other pro-serotonergic agents (e.g., triptans, linezolid, lithium, tramadol, dextromethorphan) that cannot be discontinued per protocol-defined washout. Other psychotropics: Unstable doses of antipsychotics, mood stabilizers, or long-acting benzodiazepines within the last 2 weeks; need for medications that would compromise blinding on the dosing day. Psychotherapy changes: Initiation or major change in psychotherapy within 2 weeks prior to baseline (to preserve clinical stability). Medical conditions: Clinically significant or unstable medical illness (cardiovascular, neurological, hepatic, renal), prolonged QTc, known hypersensitivity/contraindication to fluoxetine or study materials. Pregnancy or breastfeeding. Substance use: Current substance use disorder (excluding nicotine/caffeine) within the past 3 months; non-medical cannabis use that cannot meet the pre-dose abstinence window (e.g., ≥72 h). Any condition that, in the investigator's opinion, would make participation unsafe or interfere with the assessments. Washout note (to include in Procedures/Eligibility): SSRIs/SNRIs: 7 days or ≥5 half-lives; prior fluoxetine: ≥6 weeks; MAOIs: ≥14 days before randomization/dosing. Participants must be willing and able to follow the washout schedule.

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