Compass Pathways has reported positive six-month results from its second Phase 3 trial evaluating COMP360, its synthetic psilocybin formulation, in adults with treatment-resistant depression (TRD).

The findings from the ongoing COMP006 study reinforce previously reported Phase 3 data, demonstrating rapid symptom improvement and sustained benefit for up to 26 weeks while maintaining a generally well-tolerated safety profile.

The trial enrolled nearly 600 participants with highly chronic treatment-resistant depression, with patients experiencing depressive episodes lasting an average of more than three years and more than six lifetime depressive episodes.

Compass said participants receiving two 25 mg doses of COMP360 maintained clinically meaningful improvements through at least six months.

According to the company, 39% of patients receiving the 25 mg dose achieved a clinically meaningful reduction in depression severity by Week 6 and maintained that response through Week 26. The results compare with previously reported findings from the Phase 3 COMP005 study, where 25% of participants maintained a clinically meaningful response following a single dose, suggesting additional benefit from a second treatment in some patients.

The study also found that almost 30% of patients who responded following initial treatment went on to achieve remission after retreatment during the second part of the trial.

Safety findings remained consistent with previous studies. The majority of treatment-emergent adverse events were transient and occurred on the day of dosing, with nausea, headache, anxiety and visual hallucinations reported as the most common events. Serious adverse events were reported at similar rates in both treatment groups, and the company said no new safety findings were identified.

Compass is conducting a rolling New Drug Application submission with the FDA and expects to complete its regulatory filing during the fourth quarter of 2026. If approved and following rescheduling by the US Drug Enforcement Administration, the company expects to launch COMP360 during the first half of 2027.

Kabir Nath, chief executive officer of Compass Pathways, said: “The COMP006 data further strengthens our robust clinical package for COMP360 and represents an important step toward completing our NDA submission.”

He added: “COMP360 has demonstrated consistent results, with rapid onset and durable benefit for people living with chronic, treatment-resistant depression.”

Treatment-resistant depression affects people whose symptoms do not respond adequately to multiple antidepressant therapies and remains one of the most difficult psychiatric conditions to treat.

Compass said the positive findings from COMP006, together with the earlier COMP005 trial, represent the first time a classic psychedelic has demonstrated consistent Phase 3 evidence of rapid onset, durable clinical benefit and reproducible efficacy in treatment-resistant depression.

Alongside preparations for a potential regulatory approval, the company is continuing development of COMP360 while progressing its late-stage clinical programme investigating the therapy in post-traumatic stress disorder.