UK-based Compass Pathways announced positive topline results from its second pivotal Phase III clinical trial evaluating COMP360, a proprietary crystalline formulation of psilocybin, in patients with treatment-resistant depression (TRD). The study met its primary endpoint, demonstrating a statistically significant improvement in depressive symptoms compared to the control group. This development places COMP360, which is administered in conjunction with psychological support, closer to potentially becoming the first psychedelic-derived therapy approved for TRD, a condition affecting millions of patients who do not respond to existing pharmacological interventions.

Trial specifics

The Phase III study was a randomized, double-blind, multicenter trial designed to evaluate the efficacy and safety of COMP360 psilocybin therapy in adults with treatment-resistant depression. Patients were randomized to receive either a 25 mg dose of COMP360 or a control treatment, both administered with psychological support from trained therapists. The primary endpoint was the change from baseline in the Montgomery-Åsberg Depression Rating Scale (MADRS) total score at Week 6. The company reported that the 25 mg COMP360 arm achieved a statistically significant reduction in MADRS scores compared to the control arm, validating the efficacy signal observed in previous studies.

Regarding safety, the company stated that COMP360 was generally well-tolerated. The adverse event profile was consistent with prior studies of psilocybin, with the most common treatment-emergent adverse events including headache, nausea, and transient acute psychedelic effects known as potential risks of the drug class. No new safety signals were identified. Based on these data, combined with results from the earlier Phase III COMP005 trial, Compass Pathways indicated it intends to finalize its regulatory data package. The company plans to submit a New Drug Application (NDA) to the US FDA in the second half of 2026.

Research context

COMP360 is a synthesized formulation of psilocybin, a psychoactive compound that acts primarily as a partial agonist at the 5-HT2A serotonin receptor. The therapeutic hypothesis suggests that psilocybin, when paired with psychological support, induces a state of heightened neuroplasticity that allows patients to disrupt rigid, negative thought patterns associated with depression. This mechanism differs fundamentally from chronic daily maintenance with selective serotonin reuptake inhibitors (SSRIs), offering a rapid-onset, episodic treatment model for patients who have failed at least two prior antidepressant therapies. The US FDA previously granted COMP360 Breakthrough Therapy designation for this indication, a reflection of the significant unmet need in the TRD population.

The landscape for psychedelic and rapid-acting antidepressants has become increasingly active, with several companies targeting similar pathways. Key competitors include:

• Johnson & Johnson’s Spravato (esketamine), an NMDA receptor antagonist delivered as an intranasal spray, which is currently the only approved rapid-acting dissociation-inducing therapy for treatment-resistant depression.
• Usona Institute’s psilocybin, a non-profit led program developing a synthetic psilocybin formulation for major depressive disorder (MDD) which is currently in Phase III development.
• Cybin Inc.’s CYB003, a deuterated psilocybin analog designed to offer a shorter duration of effect and reduced variability, which is advancing through Phase III studies for major depressive disorder.
• Lykos Therapeutics (formerly MAPS PBC), which has focused on midomafetamine (MDMA) for PTSD, though its regulatory pathway provides a precedent for the drug-device combination frameworks required for psychedelic-assisted therapies.