A Phase III, Multicentre, Randomised, Double-blind, Placebo-controlled Study to Investigate the Efficacy, Safety, and Tolerability of COMP360 in Participants With Treatment-resistant Depression

Efficacy, Safety, and Tolerability of a single administration of COMP360 in participants with treatment-resistant depression (TRD) This is a phase III, international, multi-centre, randomised, parallel group, fixed single-dose, double-blind, placebo-controlled study. The study population will include participants aged ≥18 years with TRD. Overall, 255 participants will be randomised in a 2:1 ratio to receive COMP360 25 mg or placebo. The study comprises three parts (A, B, and C) and will last approximately 62 weeks including a three- to ten-week Screening Period. Part A will include a six-week follow-up from initial investigational product (IP) administration. In this study, the primary aim is to assess the efficacy and safety of a single dose of COMP360 25 mg versus placebo for reducing symptom severity in TRD, when administered with psychological support. This will be assessed in a 6-week, single-dose, double-blind, placebo-controlled part of the study (Part A). Durability of efficacy and long-term safety, and the efficacy and safety of re-treatment will be assessed in a 20-week single-dose, double-blind re-treatment part (Part B), and a 26-week open-label treatment part (Part C).