COMP360 six-month data: 39% of patients on the 25 mg dose maintained their response

THE DISPATCH

In July, Compass Pathways released the complete six-month dataset from its second Phase 3 trial of synthetic psilocybin (COMP360) for treatment-resistant depression. It's the most detailed durability picture this compound has produced to date.¹ On the 25 mg dose, 39 percent of participants had a clinically meaningful response at week 6 and maintained it, on average, through week 26. Among week 6 responders who had not yet reached remission, 28 percent got there after retreatment during the trial's blinded 26-week follow-up.¹ The clinical question this newsletter has tracked since spring, whether the effect lasts, now has a provisional answer. The new question is narrower and more practical: what happens, procedurally and financially, when a patient needs retreatment outside a research protocol?

In this issue:

→ What the six-month data shows, and what "durable" means here, precisely

→ The retreatment finding, and why it points straight at a billing problem nobody has solved

→ Where the reimbursement infrastructure stands today, and where it doesn't

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THE SCIENCE

Compass Pathways' second Phase 3 trial, COMP006, enrolled 581 participants with treatment-resistant depression. On average, participants were in a current depressive episode lasting more than three years and had made more than six prior treatment attempts over their lifetime.¹ They were randomized to 25 mg (296 participants), 10 mg (142), or 1 mg (143) of synthetic psilocybin, given as two fixed doses three weeks apart. The 10 mg and 1 mg arms served as active comparators, not an inert placebo.² At the week 6 primary endpoint, depression severity on the Montgomery-Åsberg Depression Rating Scale (MADRS) fell 3.8 points more in the 25 mg arm than in the 1 mg arm, a statistically significant difference (p<0.001).² That between-arm comparison, rather than the response rate within the 25 mg arm alone, is the trial's estimate of the drug's specific contribution, although functional unblinding remains a known methodological challenge in psychedelic trials, even with active low-dose comparators.

The July data extends that picture to week 26. Thirty-nine percent of the 25 mg arm, 116 of 296 participants, had a clinically meaningful response at week 6 and maintained that benefit, on average, through week 26.¹ "Clinically meaningful" has a specific definition here: a reduction of at least 25 percent in MADRS score. That's a lower bar than the 50 percent reduction commonly used to define "response" in depression trials, and it matters when comparing this figure with other studies.

The retreatment finding is the part worth sitting with longest. Among the 68 participants in the 25 mg arm who had a clinically meaningful response at week 6 but had not yet reached remission, 28 percent went on to reach remission after an additional dose during Part B, the trial's blinded follow-up period.³ Remission here means a MADRS score of 12 or below, with no single item scored 4 or higher. Compass has not published how many of those 68 participants actually took the additional dose, and the company describes this as a post hoc analysis, so the figure is best read as a provisional signal until the full dataset appears in a peer-reviewed paper. Even so, it's the practical core of this release: the first Phase 3 signal that a course of COMP360 may not be a one-time treatment event, but potentially the start of a maintenance model, with further doses given when response fades rather than on a fixed schedule. Safety through 26 weeks stayed consistent with the earlier data. Serious adverse events occurred in 5.7 percent of the 25 mg arm and 6.3 percent of the 1 mg arm, with no new safety signal at the higher dose.¹

This is where the clinical finding runs into an infrastructure problem this newsletter has flagged for months, with little movement to report. A psilocybin-assisted session is not a pill. It requires a supervised six-to-eight-hour administration with trained clinical staff present throughout, a delivery model with no equivalent in standard psychiatric billing. The billing infrastructure insurers use to process claims is only partly in place. The American Medical Association's Category III Current Procedural Terminology (CPT) codes for monitoring during psychedelic medication therapy (0820T to 0822T) took effect in January 2024, but Category III codes are temporary tracking codes without the established payment values that routine reimbursement depends on.⁸ Diagnoses are already coded under ICD-10, and drug-specific HCPCS codes typically follow FDA approval. Compass's rolling FDA submission remains on track for the fourth quarter of 2026, and a Commissioner's National Priority Voucher (CNPV) could compress the review that follows to as little as one to two months.⁴ But FDA approval answers only one question: whether the drug can be prescribed. It doesn't answer whether, or how, a clinician gets paid for the supervised hours the treatment requires, or how a patient who needs retreatment months after a first course gets it covered. That billing gap is still open.

The esketamine precedent, discussed in this newsletter previously, showed that a novel psychiatric therapy can move from FDA approval to meaningful insurance coverage within one to two years when the delivery model is relatively contained: a supervised session plus two hours of monitoring. Psilocybin's supervised window runs three to four times longer. The retreatment data doesn't change the substance of that gap. If anything, a therapy that may need to be given again when response fades makes solving it more urgent, since the billing question would then come up for the same patient more than once.

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THE STORY

The clinical picture from this July's data release is specific. A two-dose course of synthetic psilocybin was followed by a clinically meaningful antidepressant response (at least a 25 percent drop in MADRS score) in close to four in ten patients on the 25 mg dose, and that response held, on average, through six months. For context, these were patients who had, on average, made more than six previous treatment attempts. Among early responders who had not yet reached remission, 28 percent got there after retreatment.³ It's a meaningful, if still provisional, durability signal from a Phase 3 trial with 581 participants.

The gap sitting next to that data is just as concrete, and it belongs to no single actor. Only temporary Category III tracking codes exist for supervised psychedelic-assisted therapy, so no insurer, public or private, yet has an established, valued way to pay for the session hours this treatment requires, let alone a retreatment session.⁸ No single company, regulator, or insurer created this gap. It predates this data, and this data doesn't close it on its own.

Here's what is moving. Compass's rolling NDA submission continues toward its targeted fourth-quarter 2026 filing, and the CNPV program remains in place to compress the review that follows.⁴ Billing infrastructure typically follows regulatory approval rather than coming before it, which is why the gap tends to widen right after the news gets most exciting. Watch CMS and the relevant professional coding bodies over the next two quarters for any move toward permanent Category I codes. That signal, more than the approval news itself, will decide how quickly this durability data becomes something a patient can actually use more than once.

Rose Hill Life Sciences is a psychedelic research organization – specializing in the production and research of Psilocybe cubensis operating at the intersection of science and therapeutic integration.

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ON OUR RADAR

① Compass's Rolling NDA Stays on Its Q4 Timeline

Compass confirmed in its August 5, 2026 earnings release that its rolling FDA submission for treatment-resistant depression remains on track, backed by $433.3 million in cash the company says funds it through a targeted first-half 2027 launch.⁵ No new coding or reimbursement proposal was announced alongside it.

② Compass's Separate PTSD Trial Adds a Second Retreatment Question

COMP202, Compass's dedicated PTSD trial, includes its own open-label extension offering eligible participants one retreatment dose. That's the same structural question this issue's depression data raises, now being tested in a second diagnosis.⁶

③ A Different Compound, the Same Reimbursement Question Ahead

Otsuka's acquisition of Transcend Therapeutics, agreed in March 2026 for up to $1.225 billion and completed that June, centers on TSND-201, a PTSD candidate that recently completed Phase 2 and is entering Phase 3 recruitment.⁷ It's a different molecule, not a 5-HT2A agonist, but any supervised-session psychiatric therapy that eventually reaches approval will need this same billing infrastructure built first.

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YOU ASKED

Q: "If a patient of mine responds well to psilocybin-assisted therapy once it's approved, and the effect fades after six months, what actually happens next under current billing?"

Today, very little is structured. Temporary Category III CPT codes for monitoring during psychedelic medication therapy have existed since January 2024, but they are tracking codes without established payment values, so once the drug itself is FDA approved, there will not yet be a routine way for a clinician to be reimbursed for a first course, let alone a retreatment.⁸ In practice, a clinic offering retreatment would have to negotiate payment directly with the patient or a self-insured employer plan until coding catches up. Access looked similar in the early years after esketamine's 2019 approval, though psilocybin's longer supervised session makes the coding problem more complex. The retreatment data in this issue is a provisional answer to a clinical question. Billing is a separate, unresolved question, and patients deserve to hear honestly that the two don't move on the same timeline.

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This week's takeaway: Compass's six-month data points to a durable antidepressant response following a two-dose course of synthetic psilocybin, and to a meaningful chance of remission after retreatment. Both findings are still provisional until peer review. The billing infrastructure needed to pay for that treatment, or for a retreatment, doesn't exist yet, and nothing in this data changes that timeline.

A question worth sitting with: If a therapy's own trial data suggests patients may need it more than once, does building the reimbursement infrastructure before approval become a clinical necessity rather than an administrative convenience?

Read the full data release directly: Compass Pathways: Six-Month Data from Second Phase 3 Trial

If a patient has asked you about psilocybin and you weren't sure where to point them, this is the source. Forward it to one colleague fielding the same question.

— Rotem Petranker

PhD, Clinician and Psychedelic Researcher

Advancing the development of novel psychedelic-based therapeutics

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FOOTNOTES

¹ Compass Pathways. "Compass Pathways Announces Six-Month Data from Second Phase 3 Trial Confirming Rapid and Durable Profile." July 7, 2026. https://ir.compasspathways.com/News--Events-/news/news-details/2026/Compass-Pathways-Announces-Six-Month-Data-from-Second-Phase-3-Trial-Confirming-Rapid-and-Durable-Profile/default.aspx

² Compass Pathways. "Compass Pathways Successfully Achieves Primary Endpoint in Second Phase 3 Trial Evaluating COMP360 Psilocybin for Treatment-Resistant Depression." February 17, 2026. https://ir.compasspathways.com/News--Events-/news/news-details/2026/Compass-Pathways-Successfully-Achieves-Primary-Endpoint-in-Second-Phase-3-Trial-Evaluating-COMP360-Psilocybin-for-Treatment-Resistant-Depression/default.aspx

³ Compass Pathways. "Phase 3 COMP006 Data Review" (investor webcast presentation), slide 13. July 7, 2026. https://s204.q4cdn.com/927483861/files/doc_events/2026/Phase-3-006-data-webcast-presentation-7-July-26.pdf

⁴ Compass Pathways. "Compass Pathways Announces FDA Granted NDA Rolling Review Request and Awarded Commissioner's National Priority Voucher." 2026. https://ir.compasspathways.com/News--Events-/news/news-details/2026/Compass-Pathways-Announces-FDA-Granted-NDA-Rolling-Review-Request-and-Awarded-Commissioners-National-Priority-Voucher/default.aspx

⁵ Compass Pathways. "Compass Pathways Announces Second Quarter and First Half 2026 Financial Results and Business Highlights." August 5, 2026. https://ir.compasspathways.com/News--Events-/news/news-details/2026/Compass-Pathways-Announces-Second-Quarter-and-First-Half-2026-Financial-Results-and-Business-Highlights/default.aspx

⁶ Compass Pathways. "Compass Pathways Announces FDA Acceptance of IND Application for PTSD and Hosts Webinar on PTSD and TRD." January 7, 2026. https://ir.compasspathways.com/News--Events-/news/news-details/2026/Compass-Pathways-Announces-FDA-Acceptance-of-IND-Application-for-PTSD-and-Hosts-Webinar-on-PTSD-and-TRD/default.aspx

⁷ Otsuka Pharmaceutical Co., Ltd. "Otsuka Pharmaceutical to Acquire Transcend Therapeutics." March 27, 2026, completed June 15, 2026. https://www.otsuka.co.jp/en/company/newsreleases/2026/20260327_2.html

⁸ MAPS Public Benefit Corporation. "MAPS PBC Announces New American Medical Association CPT III Codes for Psychedelic-Assisted Therapies Take Effect." January 2024. https://www.prnewswire.com/news-releases/maps-pbc-announces-new-american-medical-association-cpt-iii-codes-for-psychedelic-assisted-therapies-take-effect-302024227.html

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