Clinical TrialTreatment-Resistant Depression (TRD)PsilocybinPsilocybinPsilocybinCompleted

The Safety and Efficacy of Psilocybin in Participants With Treatment Resistant Depression

This Phase II, randomised, quadruple-blind, parallel-group, dose-ranging trial (n=233) evaluated the safety and efficacy of psilocybin in adults aged 18 and over with treatment-resistant depression (TRD). Sponsored by COMPASS Pathways and conducted across 25 sites in the United States, Canada, and multiple European countries, the study compared three psilocybin dose levels (low, medium, and high) to identify an optimal therapeutic dose for this population.

Target Enrollment
233 participants
Study Type
Phase II interventional
Design
Randomized, quadruple Blind

Detailed Description

Randomized, parallel-group, quadruple-blind, dose-ranging Phase II trial of psilocybin for treatment-resistant depression with three experimental dose arms (low, medium, high); psychotherapy provided alongside dosing.

Multi-centre study (sites in the United States, Canada and several European countries) assessing safety and efficacy outcomes in adults with TRD; actual enrolment reported as 233.

Study Protocol

Preparation

sessions

Dosing

sessions

Integration

sessions

Therapeutic Protocol

supportive

Study Arms & Interventions

Low dose

experimental

Low dose Psilocybin.

Interventions

  • Psilocybin1 mg
    via Oralsingle dose1 doses total

    Dose-finding, low dose arm per protocol.

Medium dose

experimental

Medium dose Psilocybin.

Interventions

  • Psilocybin10 mg
    via Oralsingle dose1 doses total

    Dose-finding, medium dose arm per protocol.

High dose

experimental

High dose Psilocybin.

Interventions

  • Psilocybin25
    via Oralsingle dose1 doses total

    Dose-finding, high dose arm per protocol.

Participants

Ages
1899
Sexes
Male & Female

Inclusion Criteria

  • Participants meeting all the following inclusion criteria at Screening (V1) should be
  • considered for admission into the study
  • 1. Signed ICF.
  • 2. 18 years of age or older at Screening (V1).
  • 3. At least moderate MDD (single or recurrent episode as informed by DSM-5; if single episode, duration of ≥ 3 months and ≤ 2 years) based on medical records, clinical assessment and documented completion of the version 7.0.2 MINI.
  • 4. HAM-D-17 (17-item) score ≥ 18 at Screening (V1) and at Baseline (V2).
  • 5. Failure to respond to an adequate dose and duration of 2, 3, or 4 pharmacological treatment for the current episode as determined through the MGH-ATRQ and using the supplementary advice on additional antidepressants not included in MGH-ATRQ (Appendix III). Augmentation with an add-on treatment counts as a second treatment, provided it is approved for the adjunctive treatment of MDD in that country.
  • 6. McLean Screening Instrument for Borderline Personality Disorder < 7 at
  • Screening (V1).
  • 7. Have successfully discontinued all antidepressant medications at least 2 weeks prior to Baseline (V2).
  • 8. Ability to complete all protocol required assessment tools without any assistance or alteration to the copyrighted assessments, and to comply with all study visits.

Exclusion Criteria

  • Participants meeting any of the following exclusion criteria at Screening (V1) will not be enrolled in the study.
  • Psychiatric Exclusion Criteria:
  • 1. Current or past history of schizophrenia, psychotic disorder (unless substance induced or due to a medical condition), bipolar disorder, delusional disorder, paranoid personality disorder, schizoaffective disorder, borderline personality disorder, or any serious psychiatric comorbidity as assessed by medical history and a structured clinical interview (version 7.0.2 MINI).
  • 2. Prior electroconvulsive therapy and/or ketamine for current episode.
  • 3. Current cognitive behavioural therapy (CBT) that will not remain stable for the duration of the study. CBT cannot be initiated within 21 days of baseline.
  • 4. Current (within the last year) alcohol or substance abuse as informed by DSM-5 at Screening (V1).
  • 5. Significant suicide risk as defined by (1) suicidal ideation as endorsed on items 4 or 5 on the C-SSRS within the past year, at Screening or at Baseline, or;
  • (2) suicidal behaviors within the past year, or; (3) clinical assessment of significant suicidal risk during subject interview.
  • 6. Depression secondary to other severe medical conditions.
  • 7. Other personal circumstances and behaviour judged to be incompatible with establishment of rapport or safe exposure to psilocybin, including exposure to psilocybin within the past year and use of psychedelics, such as ayahuasca, during the current depressive episode.
  • General Medical Exclusion Criteria:
  • 8. Women who are pregnant, nursing, or planning a pregnancy. Participants who are sexually active must agree to use a highly effective contraceptive method throughout their participation in the study. Women of child bearing potential must have a negative urine pregnancy test at Screening (V1) and Baseline (V2).
  • 9. Cardiovascular conditions: recent stroke (< 1 year from signing of ICF), recent myocardial infarction (< 1 year from signing of ICF), hypertension (blood pressure > 140/90 mmHg) or clinically significant arrhythmia within 1 year of signing the ICF.
  • 10. Uncontrolled insulin-dependent diabetes.
  • 11. Seizure disorder.
  • 12. Positive urine drug screen for illicit drugs or drugs of abuse at V1 and/or V2. Any positive urine drug test will be reviewed with participants to determine the pattern of use and eligibility will be determined at the investigator’s discretion in conjunction with the medical monitor.
  • 13. Current enrolment in any investigational drug or device study or participation in such within 30 days of Screening (V1).
  • 14. Current enrolment in an interventional study for depression or participation in such within 30 days of Screening (V1).
  • 15. Abnormal and clinically significant results on the physical examination, vital signs, ECG, or laboratory tests at Screening (V1).
  • 16. Any other clinically significant cardiovascular, pulmonary, gastrointestinal, hepatic, renal or any other major concurrent illness that, in the opinion of the investigator, may interfere with the interpretation of the study results or constitute a health risk for the participant if he/she takes part in the study

Primary Results(6 publications)

Participants

N = 233Mean age: 38.7–40.6 across armsM. et al. 2022
N = 77Mean age: 30.6–33.1 across armsL. et al. 2024
N = 233Mean age: 38.7–40.6 across armsN. et al. 2025
N = 233Mean age: 39.8 across armsM. et al. 2026

Adverse Events (from all publications)

Arm / GroupnAny TEAESevereSeriousDiscont.
Low doseexperimental7966(83.5%)13(16.5%)10(12.7%)2(2.5%)
Medium doseexperimental7556(74.7%)10(13.3%)6(8.0%)2(2.7%)
High doseexperimental7957(72.2%)2(2.5%)1(1.3%)0(0.0%)
Low doseexperimental4
Medium doseexperimental3
High doseexperimental4
Low doseexperimental26
Medium doseexperimental24
High doseexperimental27
Low doseexperimental79
Medium doseexperimental75
High doseexperimental79
Low doseexperimental79
Medium doseexperimental75
High doseexperimental79
Low doseexperimental79
Medium doseexperimental75
High doseexperimental79

* teaeAny_n (84%) and teaeSerious_n (13% total across all periods) derived from text and Table 3. teaeDiscont_n refers to those discontinuing due to adverse events specifically. Suicidal ideation/behavior and self-injury are included in serious AE counts.

* teaeAny_n (75%) and teaeSerious_n (8% day 1 + 5% day 2-3 + 4% week 3-12) derived from text and Table 3. teaeDiscont_n refers to those discontinuing due to adverse events specifically.

* teaeAny_n (72%) and teaeSerious_n (1% day 1 + 1% day 2-3 + 1% week 3-12) derived from text and Table 3. teaeDiscont_n refers to those discontinuing due to adverse events specifically.

* 1 mg dose group (active control). Qualitative study of 11 participants; 4 were in this arm.

* 10 mg dose group. Qualitative study of 11 participants; 3 were in this arm.

* 25 mg dose group. Qualitative study of 11 participants; 4 were in this arm.

* 25 mg dose group (from Table 2). Safety summary counts not explicitly provided in the text/tables.

* 10 mg dose group (from Table 2). Safety summary counts not explicitly provided in the text/tables.

* 1 mg dose group (from Table 2). Safety summary counts not explicitly provided in the text/tables.

* Safety summary counts (TEAEs) not explicitly provided in the provided text/tables; only efficacy and psychedelic experience measures were reported.

* Safety summary counts not explicitly provided in the text or tables of this retrospective analysis paper.

* Safety data (TEAE counts) not reported in the provided text/tables; paper focuses on therapeutic alliance and psychedelic experience correlations.

Study Details

Study Team

Sponsors & Collaborators

Investigators

  • EM
    Ekaterina Malievskaia

Locations

Kadima Neuropsychiatry InstituteLa Jolla, California, United States
Altman Clinical and Translational Research Institute, University of CaliforniaSan Diego, California, United States
Stanford Department of PsychiatryStanford, California, United States
Mood and Anxiety Disorders Program Emory University School of MedicineAtlanta, Georgia, United States
Ray Worthy Psychiatry LLCNew Orleans, Louisiana, United States
Sheppard Pratt Health SystemBaltimore, Maryland, United States
New York State Psychiatric InstituteNew York, New York, United States
UT Center of Excellence on Mood Disorders, University of Texas Health Science CenterHouston, Texas, United States
Canadian Rapid Treatment Centre of ExcellenceMississauga, Ontario, Canada
Centre for Addiction and Mental HealthToronto, Ontario, Canada
National Institute of Mental Health Czech RepublicKlecany, Czechia
Enhed for Psykiatrisk Forskning, Psykiatrien i AalborgAalborg, Denmark
Charité - Universitätsmedizin Berlin, Department of Psychiatry and Psychotherapy, Campus Benjamin FranklinBerlin, Germany
Tallaght University HospitalDublin, Ireland
Groningen University Medical CentreGroningen, Netherlands
Leiden University Medical CentreLeiden, Netherlands
Utrecht University Medical CentreUtrecht, Netherlands
Unidade de Neuropsiquiatria, Centro Clinico ChampalimaudLisbon, Portugal
Hospital de Dia NumanciaBarcelona, Spain
Institute Hospital del Mar of Medical Research (IMIM)Barcelona, Spain
Clinical Research and Imaging CentreBristol, Avon, United Kingdom
Wolfson Research Centre, Campus for Ageing and VitalityNewcastle upon Tyne, Tyne and Wear, United Kingdom
St. Pancras Clinical ResearchLondon, United Kingdom
Kings College London, Institute of Psychiatry, Psychology and NeurologyLondon, United Kingdom
Greater Manchester Mental Health Foundation TrustManchester, United Kingdom

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