Psychedelics And Treatment-Resistant Depression: An Overview Of COMPASS' Latest Trial Outcomes

(Part one of a four-part series)

Results from COMPASS Pathways CMPS’ Phase 2b trial assessing the safety of different doses of proprietary synthetic psilocybin paired with psychotherapy for Treatment-Resistant Depression (TRD) were recently published in the New England Journal of Medicine. 

The study took place at 22 sites in the US, Canada, the UK and seven European countries and enrolled 233 participants who had TRD, meaning they had not responded to two prior courses of antidepressants.

Noting data that approximately 100 million people globally have TRD and, of the nine million in the U.S. with medically treated depression, an estimated one-third of them, or three million, are resistant to treatment. As the publication explains, people with this condition are at a high risk of physical illness, disability, hospitalization and suicide. 

Double-blind and randomized, the trial divided participants into three groups, corresponding to a single administration of COMP360 at 25mg, 10mg, or 1mg (control) doses, together with psychological support. 

As stated, this is the largest published psilocybin trial to date and the second major psilocybin study published in the prestigious journal (following 2021’s psilocybin vs. escitalopram.) 

Outcomes following the single administration included an immediate improvement of depression scores for most patients in all groups, showing profound antidepressant effects for those in the 25mg dose arm.

After 3 weeks, 29% of subjects in the 25mg dose group, 9% in the 10mg group and 8% in the 1mg group were responsive. The first cipher, despite being relatively high, is lower compared to the one described for first-line treatment of Major Depressive Disorder (MDD) in large trials of citalopram and other conventional antidepressants yet higher than second-line treatments. 

At week 12, the number of responders in the high-dose group was at 20% and 10% in the lowest dose group. 

On the other hand, adverse events occurred in 77% of total participants spanning all three groups; these included headache, nausea, dizziness, fatigue and in some cases, suicidal ideation or behavior or self-injury -rates of suicidality were found in participants at 1% at 1mg,  4% at 10mg and 5% at 25mg.

The study authors said that larger and longer trials, including comparison with existing treatments, are required to further determine the efficacy and safety of psilocybin for TRD. Indeed, longer-term follow-up of these patients will be key to establishing the durability of psilocybin therapy’s effects. 

In this sense, COMPASS is already set to conduct larger phase 3 trials exploring the effects of two doses of psilocybin beginning in December 2022. Expected to include over 900 participants in 14 countries, the study is projected to wrap up by mid-2025.

Next up: Psychedelics And Treatment-Resistant Depression: Reactions On Published Results

Image by Engin Akyurt from Pixabay