New 52-Week Topline Open-Label Data from Phase 3 COMP005 Trial: The Power of Another COMP360 Dose

Compass Pathways today announced the topline 52-week results (Part C) from its phase 3 COMP005 trial of COMP360, a synthetic formulation of psilocybin, for the management of treatment-resistant depression (TRD).¹ These results further support COMP360’s differentiated profile and potential for long lasting benefit. The open-label Part C data demonstrate 4 important findings:

1. Notable additional benefit was observed with an added reduction in MADRS score leading to an average 13-point reduction from baseline at week 52 and extended out to 1 year for participants who were randomly assigned to the 25 mg arm and received an additional dose in Part C.
2. For participants in the placebo arm who received their first dose of COMP360 25 mg in Part C, these findings further reinforce that a single dose of 25 mg has the potential to produce rapid onset, meaningful effect and durability.
3. For all participants in Part C who received a 25 mg dose, strong response and remission rates were observed with 40% to 45% responders and approximately 30% remitters across all timepoints in the 6 weeks following the Part C dose.
4. The COMP360 safety profile in Part C is consistent with Parts A and B and continues to show a generally well-tolerated and safe profile with no new safety findings.

“COMP360 has now demonstrated rapid onset, substantial magnitude of effect and sustained durability through one year with just a few doses. This emerging clinical profile is unmatched in TRD and puts COMP360 in a league of its own,” said Kabir Nath, the chief executive officer of Compass Pathways. “We are excited for what this means for TRD patients and for those who care for them and the potential to move beyond treatments that require daily or frequent administration.

More About the COMP005 Trial

The COMP005 trial was a randomized, double-blind, placebo-controlled study assessing the safety and efficacy of a single dose of 25 mg COMP360 compared with placebo for reducing symptom severity in TRD. Investigators enrolled 258 participants in the United States.

The trial was broken down into 3 parts:

• Part A: Blinded through week 6; Eligible participants were randomly assigned (2:1) to receive a single dose of 25 mg of COMP360 or placebo.
• Part B: Blinded from weeks 6 to 26; Eligible participants could receive an additional dose of the same treatment to which they were originally randomized.
• Part C: Open-label from week 26 to 52; Eligible participants from both dosing arms could receive a single dose of 25 mg.

Approximately 70% of the study participants continued beyond week 26 and entered Part C. In the 25 mg arm, approximately 80% (n=90) who entered Part C received an additional open-label dose. This was their second or third dose depending on whether they received an additional dose in Part B. In the placebo arm, approximately 90% (n=52) who entered Part C received an open-label 25 mg dose. This was their first dose of COMP360 25 mg given they received placebo in parts A and B.

“These 52-week results show COMP360, if approved, has the potential to be truly life changing for TRD patients. The consistent, rapid onset, pronounced magnitude of effect and durability to one year are remarkable to see, especially in such a chronic TRD population,” said Guy Goodwin, MD, the chief medical officer of Compass Pathways. “TRD remains one of the most challenging conditions in psychiatry to treat, and these results further reinforce COMP360’s highly differentiated clinical profile. Across the 52-week study period, participants experienced cumulative and sustained reductions in depressive symptoms, which represent a significant advancement for the field. Importantly, we are especially excited to see the trends in the open-label Part C of this trial, with continued benefit and high rates of response and remission, which we believe is a closer representation of how COMP360 will be used in real-world clinical practice. For people living with TRD, and for the clinicians committed to helping them, we believe COMP360 has the potential to reshape expectations for treatment and provide long-term benefit.”

The Ongoing COMP006 Trial

COMP006, the second part of the COMP360 phase 3 program, is a randomized, double-blind study with 581 dosed participants across North America and Europe that is comparing the efficacy and safety of 2 fixed doses, taken 3 weeks apart, of 25 mg COMP360 to 10 mg COMP360 and 1 mg COMP360 (25 mg: n=296; 10 mg: n=142; 1 mg: n=143). There is a potential for a total of 4 doses of COMP360 across a 52-week period. The trial is comprised of 3 parts: Part A, which was blinded through 9 weeks; Part B, which recently concluded and remained blinded through week 26; and Part C, which contains an open-label treatment part from week 26 to 52.²

Next Steps

“As we continue to advance COMP360 for patients, our rolling NDA submission and review are well underway, with final NDA submission expected in the fourth quarter and launch expected in the first half of next year, subject to FDA approval. With a robust clinical package, and growing patient and provider anticipation for COMP360 as a much-needed treatment for TRD, Compass is well-positioned and ready to deliver,” shared Nath.

References

1. Compass Pathways’ new 52-week topline open-label data from phase 3 COMP005 trial demonstrates additional benefit from another COMP360 dose in Part C extending durability out to 1 year. News release. September 9, 2026. Accessed September 9, 2026. https://ir.compasspathways.com/News--Events-/news/news-details/2026/Compass-Pathways-New-52-Week-Topline-Open-Label-Data-from-Phase-3-COMP005-Trial-Demonstrates-Additional-Benefit-from-Another-COMP360-Dose-in-Part-C-Extending-Durability-Out-to-1-Year/default.aspx

2. Kuntz L. New 6-month data from second phase 3 trial confirms rapid effect of COMP360 for TRD. Psychiatric Times. July 7, 2026. https://www.psychiatrictimes.com/view/new-6-month-data-from-second-phase-3-trial-confirms-rapid-effect-of-comp360-for-trd