Compass Pathways plc stock (NASDAQ: CMPS) declined about 11% in premarket trading on Tuesday after the company released six-month results from its second Phase 3 study of COMP360, a synthesized formulation of psilocybin being evaluated for treatment-resistant depression (TRD).
The data refer to the 26-week findings from the COMP006 trial. Nearly 600 patients enrolled in the study had highly chronic TRD, with current depressive episodes that lasted on average more than three years and more than six lifetime depressive episodes.
In the trial, participants randomized to the 25 mg dose arm experienced a clinically meaningful reduction in Montgomery-Åsberg Depression Rating Scale (MADRS) scores by week 6 following two fixed doses of COMP360; 39% met that threshold and sustained the response through week 26. By comparison, the earlier COMP005 trial, which evaluated a single dose, reported a 25% clinically meaningful response rate.
The company also reported that nearly 30% of those who had achieved a clinically meaningful response at week 6 went on to reach remission after receiving retreatment.
Safety findings for COMP360 in COMP006 were described as generally favorable, with no new safety signals identified. Most treatment-emergent adverse events were transient and occurred primarily on the day of dosing. The most commonly observed adverse events were nausea, headache, anxiety and visual hallucination. Serious adverse events were infrequent over the 26-week period, recorded at 6.3% in the 1 mg arm and 5.7% in the 25 mg arm.
Regulatory work continues in parallel with the clinical program. Compass is conducting a rolling New Drug Application submission and an initial review with the U.S. Food and Drug Administration is underway. The company expects to complete the final submission in the fourth quarter of 2026 and is targeting a potential commercial launch of COMP360 in the first half of 2027, contingent on FDA approval and any required Drug Enforcement Administration rescheduling.
Separate development efforts remain underway at Compass, including a late-stage program for post-traumatic stress disorder. The company plans to host a webinar on July 7 at 8:00 am ET to discuss aspects of its programs.
Clear summary
Compass Pathways released 26-week COMP006 trial data showing durable clinical responses for COMP360 in a population with severe, long-standing TRD. The 25 mg arm demonstrated a 39% clinically meaningful response at week 6 retained through week 26. Safety was consistent with previous findings and no new concerns were reported. A rolling NDA review with the FDA is in progress, with final submission slated for Q4 2026 and possible launch in H1 2027 if approvals and rescheduling occur. The stock reacted negatively in premarket trading.