Feasibility, Clinical Effects, and Safety of Psilocybin-assisted Psychotherapy for Treatment-resistant OCD

Overview

Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects. There is interest to see if similar effects may be provided in those with obsessive compulsive disorder (OCD). The purpose of this study is to evaluate the safety, feasibility, and clinical effects of psilocybin administration in those with OCD. Ten participants with treatment-resistant OCD will receive two doses of 25mg of psilocybin under supportive conditions, two weeks apart. The investigators hypothesize that two sessions of psilocybin 25mg administered under supportive conditions to participants with treatment-resistant OCD will lead to significant reductions in OCD symptoms.

Literature suggests that up to 40 percent of individuals with OCD do not respond to conventional treatment and experience treatment resistant OCD (TROCD) (1, 2). Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects (3). Results of these trials have led to growing calls for transition to clinical use, as well as increased research for other mental health disorders. It is presumed that psilocybin's therapeutic effects are induced by the psychedelic "trip", which is dependent on serotonin 2A receptor (5-HT2AR) activation (4, 5). All studies have used psilocybin in conjunction with psychotherapy involving two therapists present during full-day dosing sessions. There is a need for more data in the TROCD population as there is only one clinical trial published for this specific population, followed by various case reports. Using a proof-of-concept, open-label, clinical trial approach, 10 participants with TROCD will receive 2 doses of 25mg of psilocybin, with two weeks between each dosing day. The objectives of this study are as follows: 1. To assess the safety, and feasibility, of psilocybin, administered with psychological support to adult participants with TROCD. Hypothesis 1: The investigators will be able to recruit and retain ten participants with TROCD for the duration of the trial and that psychedelic-assisted psychotherapy for obsessive compulsive disorder (PAP-OCD) will be safe in those with TROCD, as measured by monitoring adverse events and using the Columbia Suicide Severity Rating Scale (C-SSRS). 2. To assess the clinical effects of PAP in those with TROCD. Hypothesis 2: Two sessions of psilocybin (25mg) administered under supportive conditions to participants with TROCD will lead to significant reductions in OCD symptoms as measured by the Yale-Brown Obsessive Compulsive Scale (YBOCS) when comparing baseline to Week 3. 3. Provide pilot data on the effect of psilocybin and supportive therapy on TROCD in preparation of a future larger RCT. Overview of Study Design: All 10 participants will follow the same study design. Each participant will undergo a screening assessment where they will complete lab tests, and clinical and psychiatric assessments to determine eligibility. Following the screening visit, participants will undergo a washout period where they will be tapered off concomitant medications over a medication the participant is being tapered off (based on the half-life of the medication) and the participant's preference for the length of the tapering period. All medications will require a minimum of a 2-week tapering period with the exception of fluoxetine which will require a minimum of 4-weeks. Additional time may be added at the discretion of the study investigator. During this period, there will be weekly check-ins with the study physician. At study Visit 2 (Baseline, V2), participants will complete a series of questionnaires and assessments, preparatory therapy with trained study therapists, and undergo a brain functional magnetic resonance imaging (fMRI). The preparatory therapy sessions will build a therapeutic alliance, and provide psychoeducation about, and set intentions for, the psilocybin session. To reduce participant burden, baseline can be broken up into multiple days, however all assessments must be completed within 7-days of the first dose. At study Visit 3 (V3), neurophysiological measurements will be performed. Upon completion of V2 and V3, participants will undergo the first psilocybin dosing session at Visit 4 (V4) where they will receive an active dose (25mg) of psilocybin in conjunction with supportive therapy. The psilocybin session will last 5 to 6 hours and will be conducted in the existing psychedelic treatment suite developed at the Centre for Addiction and Mental Health (CAMH). Two trained study therapists will be supporting each participant during the dosing session. After 5 hours of dose administration, participants will be evaluated for safety by the study psychiatrist and discharged home in the company of a caregiver or a family member. On the day after the dosing session (Visit 5, V5) and one-week after the dosing session (Visit 6, V6), participants will be asked to complete the same questionnaires that were done at Baseline (V2) and will undergo an integrative therapy session with the trained study therapist. At Visit 7 (V7), 2-weeks after the first psilocybin dose, participants will undergo the second psilocybin dosing session where they will receive an active dose (25mg) of psilocybin in conjunction with supportive therapy. On the day after the second dosing session (Visit 8, V8) and one-week after the second dosing session \[3-weeks after dose 1\] (Visit 10, V10), participants will be asked to complete the same questionnaires that were done at Baseline (V2) and will undergo an integrative therapy session with the trained study therapist. Between Visit 8 (V8) and Visit 10 (V10), during study Visit 9 (V9), the same neurophysiological measurements will be performed as during Visit 3 (V3). Follow-up assessments will also occur at 6, 9, and 12 weeks (Visit 11, 12, and 13) after the second psilocybin dosing session. The same questionnaires administered at Baseline (V2) will be repeated at each of these study visits.