Single-Dose Psilocybin Therapy Shows Durable Efficacy at 52 Weeks in Phase 3 Trial for Treatment-Resistant Depression

On September 9, 2026, clinical investigators and executives at Compass Pathways unblinded the final data lock for the 52-week extension of the COMP005 trial, revealing that a synthetic formulation of psilocybin provided sustained relief for treatment-resistant depression. The topline results from Part C of the Phase 3 study demonstrated that participants who received a 25-milligram dose of the investigational therapy, known as COMP360, maintained significant reductions in depressive symptoms for a full year. For a patient population that has historically exhausted standard pharmacotherapy, the data marks a critical milestone in moving psychedelic medicine from experimental research toward mainstream psychiatric practice.[4][5]

The COMP005 trial initially enrolled 258 participants across the United States, all of whom had failed to respond to at least two prior antidepressant treatments. The study was structured in three phases: a blinded acute phase through week six, a blinded maintenance phase through week 26, and an open-label extension—Part C—that tracked patients through week 52. Approximately 70% of the original cohort elected to continue into the final open-label period, providing researchers with one of the longest continuous datasets on psilocybin therapy to date.[3][5]

The most pronounced effects were observed among participants who were originally randomized to the 25-milligram treatment arm and received an additional dose during the open-label extension. For this group, the mean reduction in the Montgomery-Åsberg Depression Rating Scale (MADRS) reached 13 points from baseline at the 52-week mark. This sustained drop indicates that a second administration can deepen and prolong the clinical benefit for patients who only achieved a partial response after their initial session.[4][5]

Equally notable were the outcomes for the control group. Participants who were originally assigned to the placebo arm during the blinded phases, but who crossed over to receive their first 25-milligram dose of COMP360 in Part C, experienced an average 10-point reduction in their MADRS scores. This rapid onset of symptom relief mirrors the acute efficacy seen in the trial's earlier stages and reinforces the drug's primary mechanism of action when combined with psychological support.[3][5]

Across all participants who received the 25-milligram open-label dose in Part C, clinical response rates hovered between 40% and 45% in the six weeks following administration. Furthermore, approximately 30% of these patients achieved full clinical remission, a remarkably high threshold for a chronic, treatment-resistant population. "COMP360 has now demonstrated rapid onset, substantial magnitude of effect and sustained durability through one year with just a few doses," said Kabir Nath, chief executive officer of Compass Pathways.[4]

The safety profile of the synthetic psilocybin remained stable throughout the 52-week observation period. Investigators reported no new safety signals during Part C, with the adverse event profile remaining consistent with the earlier blinded phases. Most treatment-emergent adverse events, such as headache, nausea, and transient anxiety, occurred on the day of dosing and resolved quickly without requiring medical intervention.[4][5]

The durability of the response addresses one of the primary historical concerns regarding psychedelic-assisted therapy: whether the profound acute effects fade rapidly over time. "These 52-week results show COMP360, if approved, has the potential to be truly life changing for TRD patients," noted Dr. Guy Goodwin, chief medical officer of Compass Pathways. He emphasized that the consistent magnitude of effect over a one-year period is highly unusual in such a chronic patient population.[4]

The broader Phase 3 clinical program for COMP360 also includes a second, larger trial known as COMP006, which is currently evaluating 581 participants across North America and Europe. That study is comparing the efficacy of two fixed doses of 25 milligrams administered three weeks apart against lower doses of 10 milligrams and 1 milligram. The parallel generation of data is designed to answer lingering questions about optimal dosing intervals and the comparative benefit of single versus repeated administrations.[1][5]

With the 52-week data now in hand, the regulatory pathway for COMP360 is accelerating. Compass Pathways has initiated a rolling New Drug Application (NDA) submission with the U.S. Food and Drug Administration, which it expects to complete in the fourth quarter of 2026. If the FDA grants approval, the company anticipates a commercial launch in the first half of 2027, potentially establishing a new standard of care that relies on infrequent, clinic-based dosing rather than daily oral medications.[4][5]

The integration of psilocybin into public mental healthcare systems will still require significant logistical planning. The treatment model necessitates specialized clinical infrastructure, including trained therapists to provide psychological support before, during, and after the dosing session. As the field awaits the FDA's final decision, healthcare providers and regulators are already working to design the clinical frameworks needed to safely deliver this novel therapeutic class at scale.[1][2]